CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                        
                                                                                
                                                                                
     Computerized neurobehavioral testing was administered to a random          
     half-sample of examinees aged 20-59 years by a trained examiner in a       
     soundproof room in the mobile examination center (MEC).  A screening       
     questionnaire was administered to assess factors that might have           
     affected test performance.  There were no medical or safety exclusions     
     for this component.                                                        
                                                                                
     Because this examination was administered on a selected subsample in       
     the examination center, the central nervous system (CNS) sample weight     
     (WTPFCNS6) should be used for data analysis.  For more information on      
     the use of sample weights in NHANES III data analysis, refer to the        
     NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996b).           
                                                                                
     Three computerized tests were used to evaluate central nervous system      
     function.  They were:  (1) a simple reaction time test (SRTT), a basic     
     measure of motor response speed to a visual stimulus; (2) a symbol-digit   
     substitution test (SDST), a test of coding ability; and (3) a              
     serial-digit learning test (SDLT), a short-term memory test.  These        
     tests are components of the Neurobehavioral Evaluation System 2 (NES2)     
     developed by Baker and Letz (1985; Letz, 1990).  NES2 is a system of       
     computerized tests designed to assess neurobehavioral function in          
     epidemiological studies of populations with occupational or                
     environmental exposure to chemicals.                                       
                                                                                
     The tests were administered on a Compaq 286 DeskPro(TM) personal           
     computer (12.5 MHz, 80286 CPU chip) configured with 640K RAM, one          
     1.2MB floppy disk drive, one parallel port, two serial ports, a            
     standard game joystick controller board, and an Ethernet interface         
     board.  The system used the standard, detachable keyboard with a           
     custom-made wooden keyboard overlay that left only the top row of          
     digit keys exposed to prevent inadvertent contact with keys not needed     
     in the testing; it also used a standard, monochrome (green) Compaq         
     monitor.  In September 1991, between the conclusion of Phase 1 and the     
     initiation of Phase 2 data collection, the monitors were replaced with     
     comparable, new amber monitors due to a deterioration in display           
     performance.  A push-button, computer-game joystick (NES2 Joystick by      
     Neurobehavioral Systems, Inc., Winchester, MA) was used to record the      
     SRTT responses.                                                            
                                                                                
     The tests were administered by health technicians, MEC interviewers, and   
     translators who were trained to perform the testing.  Before               
     examinations began, special training sessions were held at NCHS or at      
     the offices of the contractor responsible for survey operations.           
     Training sessions also occurred at MEC sites during the survey, and        
     retraining was done approximately twice per year.  The test was            
     conducted in English or Spanish, and examinees who could not speak         
     English or Spanish were not tested.  English or Spanish language           
     instructions appeared on the computer screen for each test, and the        
     examiner also gave the instructions verbally.                              
                                                                               
                                                                                
     Translators were trained to administer the testing independently or        
     with a health technician.  The training was conducted in the MEC by a      
     Spanish-speaking health technician, Spanish-speaking NCHS staff            
     member, or Spanish-speaking MEC interviewer trained to administer the      
     CNS test.  Training for translators included reviewing the manual with     
     the trainer, performing the tests as an examinee, and administering        
     the examination in Spanish.                                                
                                                                                
     Physical comfort may have affected examinees' test results.  The air       
     conditioning in the soundproof room used for testing sometimes failed      
     to maintain an optimally comfortable room temperature.  Because of         
     this, room temperature (CNPTEMP) was recorded for use as a covariate;      
     however, this practice did not begin until the second year of the          
     survey.  The location of the thermometer within the room and the time      
     that temperature was recorded were not consistent throughout the           
     survey.  For instance, some examiners entered the temperature at the       
     beginning of the testing session, and others recorded it at the end of     
     the session.  This source of error is likely to be small.                  
                                                                                
     Initially, some trials of the SRTT were performed with both the            
     non-preferred hand and the preferred hand.  Early in the survey, the       
     procedure was changed to perform all trials only with the preferred        
     hand.  As a result, analysts may want to exclude SRTT data from those      
     examinees who used both hands for the test.  The affected data have a      
     value of "2  Non-preferred hand used on trials 31-50" for the variable     
     CNPNBPH (LOG:  Number of trials with preferred hand).                      
                                                                                
     During Phase 2 of the survey, reading glasses were available for           
     examinees who forgot to bring their own reading glasses to the MEC.        
     Examinees could select from four pairs of glasses of different             
     diopters or magnifying powers (+1.0 diopter, +1.5 diopters, +2.0           
     diopters, and +2.5 diopters).                                              
                                                                                
     Although all examiners were well-trained in standardized procedures        
     for these tests, performance on neurobehavioral tests may have been        
     subject to an examiner effect.  This would have been particularly          
     likely when the examiner encouraged the examinee during the exam, as       
     was the case in NHANES III.  Therefore, analysts should consider using     
     the examiner number (CNPTECH) as a covariate in analyses of data from      
     these tests.                                                               
                                                                                
     For details of the examination protocol, see the Neurobehavioral           
     Testing Procedures Manual (U.S. DHHS, 1996b).                              
                                                                                
     Data processing and editing were performed to ensure internal data         
     consistency.  Notes have been provided for variables requiring             
     additional explanation.                                                   
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       CONDITIONS AFFECTING TEST RESULTS                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5502          How much sleep did you get last night?               
      CNPQ01               Would you say about the usual amount,                
                           less than usual, or more than usual?                 
                   3131    1     About usual amount                             
                   1552    2     Less than usual                                
                    461    3     More than usual                                
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5503          Right now would you say you are feeling              
      CNPQ02               energetic, fresh, average, tired, or                 
                           exhausted?                                           
                    280    1     Energetic                                      
                    668    2     Fresh                                          
                   2815    3     Average                                        
                   1229    4     Tired                                          
                    152    5     Exhausted                                      
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5504          How much familiarity do you have with                
      CNPQ03               computers or video games?  Would you say             
                           none, some, or a lot?                                
                   2167    0     None                                           
                   2268    1     Some                                           
                    709    2     A lot                                          
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5505          Not counting decaffeinated products, how             
      CNPQ04               many cups of coffee, tea, or cola have               
                           you had in the past 3 hours?                         
                   4912    0     None                                           
                    164    1     One                                            
                     68    2     2 or more                                      
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       CONDITIONS AFFECTING TEST RESULTS                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5506          How many drinks of alcohol have you had              
      CNPQ05               in the past 3 hours?  Include any                    
                           alcoholic drinks such as wine, beer, or              
                           hard liquor.                                         
                   5080    0     None                                           
                     47    1     One                                            
                     17    2     2 or more                                      
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5507          Which hand do you prefer to use for this             
      CNPQ06               test?                                                
                   4720    1     Right                                          
                    424    2     Left                                           
                    518    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5508          Simple Reaction Time Test (SRTT)                     
      CNPQ07               completed                                            
                   5138    1     Yes                                            
                     63    2     No                                             
                    461    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5509          Symbol Digit Substitution Test (SDST)                
      CNPQ08               completed                                            
                   5092    1     Yes                                            
                    109    2     No                                             
                    461    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5510          Serial Digit Learning Test (SDLT)                    
      CNPQ09               completed                                            
                   4962    1     Yes                                            
                    236    2     No                                             
                    464    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       CONDITIONS AFFECTING TEST RESULTS                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5511          How hard did you try to perform this                 
      CNPQ10               computer test?                                       
                    135    0     None/not at all                                
                   1268    1     Some                                           
                   1137    2     A lot                                          
                   2596    3     As hard as I could                             
                    526    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5512          Language used for test administration                
      CNPLANG      4460    1     English                                        
                    685    2     Spanish                                        
                    517    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5513-5515          Room temperature (degrees Fahrenheit)                
      CNPTEMP      4013    060-092                                              
                   1649    888   Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5516-5520          Examiner number                                      
      CNPTECH      5207    01001-09018                                          
                    455    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5521          LOG: Number of trials with preferred                 
      CNPNBPH              hand                                                 
                   4896    1     Preferred hand used on all 50                  
                                 trials                                         
                    242    2     Non-preferred hand used on trials              
                                 31-50                                          
                    524    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5522-5525          SRTT: Trial 01 reaction time (msec)                  
      CNPRT01      5138    0064-3866                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5526-5529          SRTT: Trial 02 reaction time (msec)                  
      CNPRT02      5138    0071-3533                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5530-5533          SRTT: Trial 03 reaction time (msec)                  
      CNPRT03      5138    0050-3509                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5534-5537          SRTT: Trial 04 reaction time (msec)                  
      CNPRT04      5138    0060-3538                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5538-5541          SRTT: Trial 05 reaction time (msec)                  
      CNPRT05      5138    0103-3993                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5542-5545          SRTT: Trial 06 reaction time (msec)                  
      CNPRT06      5138    0059-1831                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5546-5549          SRTT: Trial 07 reaction time (msec)                  
      CNPRT07      5138    0081-2778                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5550-5553          SRTT: Trial 08 reaction time (msec)                  
      CNPRT08      5138    0122-3486                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5554-5557          SRTT: Trial 09 reaction time (msec)                  
      CNPRT09      5138    0054-1764                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5558-5561          SRTT: Trial 10 reaction time (msec)                  
      CNPRT10      5138    0088-1965                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5562-5565          SRTT: Trial 11 reaction time (msec)                  
      CNPRT11      5138    0056-1004                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5566-5569          SRTT: Trial 12 reaction time (msec)                  
      CNPRT12      5138    0055-1708                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5570-5573          SRTT: Trial 13 reaction time (msec)                  
      CNPRT13      5138    0059-3607                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5574-5577          SRTT: Trial 14 reaction time (msec)                  
      CNPRT14      5138    0083-2524                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5578-5581          SRTT: Trial 15 reaction time (msec)                  
      CNPRT15      5138    0137-1204                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5582-5585          SRTT: Trial 16 reaction time (msec)                  
      CNPRT16      5138    0135-1205                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5586-5589          SRTT: Trial 17 reaction time (msec)                  
      CNPRT17      5138    0106-3234                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5590-5593          SRTT: Trial 18 reaction time (msec)                  
      CNPRT18      5138    0068-1210                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5594-5597          SRTT: Trial 19 reaction time (msec)                  
      CNPRT19      5138    0068-1457                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5598-5601          SRTT: Trial 20 reaction time (msec)                  
      CNPRT20      5138    0060-2470                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5602-5605          SRTT: Trial 21 reaction time (msec)                  
      CNPRT21      5138    0072-1457                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5606-5609          SRTT: Trial 22 reaction time (msec)                  
      CNPRT22      5138    0085-1203                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5610-5613          SRTT: Trial 23 reaction time (msec)                  
      CNPRT23      5138    0118-1202                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5614-5617          SRTT: Trial 24 reaction time (msec)                  
      CNPRT24      5138    0071-2480                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5618-5621          SRTT: Trial 25 reaction time (msec)                  
      CNPRT25      5138    0051-1202                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5622-5625          SRTT: Trial 26 reaction time (msec)                  
      CNPRT26      5138    0145-2521                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5626-5629          SRTT: Trial 27 reaction time (msec)                  
      CNPRT27      5138    0061-2896                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5630-5633          SRTT: Trial 28 reaction time (msec)                  
      CNPRT28      5138    0068-3230                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5634-5637          SRTT: Trial 29 reaction time (msec)                  
      CNPRT29      5138    0098-1962                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5638-5641          SRTT: Trial 30 reaction time (msec)                  
      CNPRT30      5138    0120-3991                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5642-5645          SRTT: Trial 31 reaction time (msec)                  
      CNPRT31      5138    0062-1202                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5646-5649          SRTT: Trial 32 reaction time (msec)                  
      CNPRT32      5138    0121-1204                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5650-5653          SRTT: Trial 33 reaction time (msec)                  
      CNPRT33      5138    0092-3995                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5654-5657          SRTT: Trial 34 reaction time (msec)                  
      CNPRT34      5138    0130-3589                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5658-5661          SRTT: Trial 35 reaction time (msec)                  
      CNPRT35      5138    0130-3535                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5662-5665          SRTT: Trial 36 reaction time (msec)                  
      CNPRT36      5138    0057-1344                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5666-5669          SRTT: Trial 37 reaction time (msec)                  
      CNPRT37      5138    0052-1202                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5670-5673          SRTT: Trial 38 reaction time (msec)                  
      CNPRT38      5138    0092-1513                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5674-5677          SRTT: Trial 39 reaction time (msec)                  
      CNPRT39      5138    0120-2975                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5678-5681          SRTT: Trial 40 reaction time (msec)                  
      CNPRT40      5138    0139-2272                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5682-5685          SRTT: Trial 41 reaction time (msec)                  
      CNPRT41      5138    0076-1200                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5686-5689          SRTT: Trial 42 reaction time (msec)                  
      CNPRT42      5138    0139-3534                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5690-5693          SRTT: Trial 43 reaction time (msec)                  
      CNPRT43      5138    0063-1055                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5694-5697          SRTT: Trial 44 reaction time (msec)                  
      CNPRT44      5138    0052-1062                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5698-5701          SRTT: Trial 45 reaction time (msec)                  
      CNPRT45      5138    0125-0999                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5702-5705          SRTT: Trial 46 reaction time (msec)                  
      CNPRT46      5138    0081-1209                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                        SIMPLE REACTION TIME TEST (SRTT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5706-5709          SRTT: Trial 47 reaction time (msec)                  
      CNPRT47      5138    0120-3338                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5710-5713          SRTT: Trial 48 reaction time (msec)                  
      CNPRT48      5138    0121-2727                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5714-5717          SRTT: Trial 49 reaction time (msec)                  
      CNPRT49      5138    0085-2013                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5718-5721          SRTT: Trial 50 reaction time (msec)                  
      CNPRT50      5138    0069-1006                                            
                    524    8888  Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5722-5729          SRTT summary:  Mean reaction time (msec) See note    
      CNPMENRT     5138    00000154-660.0606                                    
                    524    88888888  Blank but applicable                       
                  25649    Blank                                                
                                                                                
        5730-5737          SRTT summary: Standard deviation of the  See note    
      CNPSDRT              reaction times (msec)                                
                   5138    010.8057-176.2465                                    
                    524    88888888  Blank but applicable                       
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5738-5739          SDST: Number of errors, trial 1                      
      CNP1ERR      3514    00    None                                           
                    821    01    1 error                                        
                    330    02    2 errors                                       
                    178    03    3 errors                                       
                    106    04    4 errors                                       
                     65    05    5 errors                                       
                     29    06    6 errors                                       
                     12    07    7 errors                                       
                     29    08    8 errors                                       
                      8    09    9 errors                                       
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5740-5744          SDST: Latency 1, trial 1 (sec)           See note    
      CNP1LAT1     5092    -54.3-043.1                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5745-5749          SDST: Latency 2, trial 1 (sec)           See note    
      CNP1LAT2     5092    -34.5-061.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5750-5754          SDST: Latency 3, trial 1 (sec)           See note    
      CNP1LAT3     5092    -43.4-038.3                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5755-5759          SDST: Latency 4, trial 1 (sec)           See note    
      CNP1LAT4     5092    -42.6-059.4                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5760-5764          SDST: Latency 5, trial 1 (sec)           See note    
      CNP1LAT5     5092    -41.7-00026                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5765-5769          SDST: Latency 6, trial 1 (sec)           See note    
      CNP1LAT6     5092    -34.9-061.5                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5770-5774          SDST: Latency 7, trial 1 (sec)           See note    
      CNP1LAT7     5092    -21.2-080.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5775-5779          SDST: Latency 8, trial 1 (sec)           See note    
      CNP1LAT8     5092    -59.2-062.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5780-5784          SDST: Latency 9, trial 1 (sec)           See note    
      CNP1LAT9     5092    -41.1-039.2                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5785-5790          SDST: Total latency, trial 1 (sec)       See note    
      CNP1TOTL     5092    011.07-212.98                                        
                    570    888888  Blank but applicable                         
                  25649    Blank                                                
                                                                                
        5791-5792          SDST summary: Number of correct                      
      CNPCORR1             responses for latencies 2 through 9,                 
                           trial 1                                              
                      8    00                                                   
                     32    01                                                   
                     24    02                                                   
                     65    03                                                   
                    106    04                                                   
                    159    05                                                   
                    316    06                                                   
                    755    07                                                   
                   3627    08                                                   
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5793-5798          SDST summary: Error-corrected latency    See note    
      CNPCLAT1             for trial 1 - total latency/number of                
                           correct responses (sec)                              
                   5084    001.38-095.68                                        
                    570    888888  Blank but applicable                         
                  25657    Blank                                                
                                                                                
        5799-5800          SDST: Number of errors, trial 2                      
      CNP2ERR      4117    00    None                                           
                    616    01    1 error                                        
                    170    02    2 errors                                       
                     90    03    3 errors                                       
                     47    04    4 errors                                       
                     27    05    5 errors                                       
                     13    06    6 errors                                       
                      4    07    7 errors                                       
                      4    08    8 errors                                       
                      4    09    9 errors                                       
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5801-5805          SDST: Latency 1, trial 2 (sec)           See note    
      CNP2LAT1     5092    -36.8-037.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5806-5810          SDST: Latency 2, trial 2 (sec)           See note    
      CNP2LAT2     5092    -48.5-057.3                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5811-5815          SDST: Latency 3, trial 2 (sec)           See note    
      CNP2LAT3     5092    -0028-00055                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5816-5820          SDST: Latency 4, trial 2 (sec)           See note    
      CNP2LAT4     5092    -18.1-099.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5821-5825          SDST: Latency 5, trial 2 (sec)           See note    
      CNP2LAT5     5092    -27.3-00048                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5826-5830          SDST: Latency 6, trial 2 (sec)           See note    
      CNP2LAT6     5092    -22.1-032.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5831-5835          SDST: Latency 7, trial 2 (sec)           See note    
      CNP2LAT7     5092    -54.9-038.3                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5836-5840          SDST: Latency 8, trial 2 (sec)           See note    
      CNP2LAT8     5092    -20.6-025.5                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5841-5845          SDST: Latency 9, trial 2 (sec)           See note    
      CNP2LAT9     5092    -86.9-052.1                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5846-5851          SDST: Total latency, trial 2 (sec)       See note    
      CNP2TOTL     5092    003.79-467.95                                        
                    570    888888  Blank but applicable                         
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5852-5853          SDST summary: Number of correct                      
      CNPCORR2             responses for latencies 2 through 9,                 
                           trial 2                                              
                      4    00                                                   
                      7    01                                                   
                     10    02                                                   
                     26    03                                                   
                     34    04                                                   
                     75    05                                                   
                    158    06                                                   
                    539    07                                                   
                   4239    08                                                   
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5854-5859          SDST summary: Error-corrected latency    See note    
      CNPCLAT2             for trial 2 - total latency/number of                
                           correct responses (sec)                              
                   5088    001.51-104.18                                        
                    570    888888  Blank but applicable                         
                  25653    Blank                                                
                                                                                
        5860-5861          SDST: Number of errors, trial 3                      
      CNP3ERR      4103    00    None                                           
                    658    01    1 error                                        
                    179    02    2 errors                                       
                     63    03    3 errors                                       
                     46    04    4 errors                                       
                     16    05    5 errors                                       
                     12    06    6 errors                                       
                      4    07    7 errors                                       
                      7    08    8 errors                                       
                      4    09    9 errors                                       
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5862-5866          SDST: Latency 1, trial 3 (sec)           See note    
      CNP3LAT1     5092    -24.4-040.1                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5867-5871          SDST: Latency 2, trial 3 (sec)           See note    
      CNP3LAT2     5092    -24.8-032.4                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5872-5876          SDST: Latency 3, trial 3 (sec)           See note    
      CNP3LAT3     5092    -23.6-042.5                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5877-5881          SDST: Latency 4, trial 3 (sec)           See note    
      CNP3LAT4     5092    -0038-041.7                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5882-5886          SDST: Latency 5, trial 3 (sec)           See note    
      CNP3LAT5     5092    -31.8-029.2                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5887-5891          SDST: Latency 6, trial 3 (sec)           See note    
      CNP3LAT6     5092    -32.2-034.6                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5892-5896          SDST: Latency 7, trial 3 (sec)           See note    
      CNP3LAT7     5092    -23.8-034.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5897-5901          SDST: Latency 8, trial 3 (sec)           See note    
      CNP3LAT8     5092    -25.4-037.7                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5902-5906          SDST: Latency 9, trial 3 (sec)           See note    
      CNP3LAT9     5092    -15.4-00027                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5907-5912          SDST: Total latency, trial 3 (sec)       See note    
      CNP3TOTL     5092    008.49-145.23                                        
                    570    888888  Blank but applicable                         
                  25649    Blank                                                
                                                                                
        5913-5914          SDST summary: Number of correct                      
      CNPCORR3             responses for latencies 2 through 9,                 
                           trial 3                                              
                      5    00                                                   
                      7    01                                                   
                     11    02                                                   
                     17    03                                                   
                     39    04                                                   
                     63    05                                                   
                    154    06                                                   
                    600    07                                                   
                   4196    08                                                   
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5915-5920          SDST summary: Error-corrected latency    See note    
      CNPCLAT3             for trial 3 - total latency/number of                
                           correct responses (sec)                              
                   5087    001.21-105.03                                        
                    570    888888  Blank but applicable                         
                  25654    Blank                                                
                                                                                
        5921-5922          SDST: Number of errors, trial 4                      
      CNP4ERR      3971    00    None                                           
                    708    01    1 error                                        
                    229    02    2 errors                                       
                    108    03    3 errors                                       
                     46    04    4 errors                                       
                     22    05    5 errors                                       
                      3    06    6 errors                                       
                      2    07    7 errors                                       
                      2    08    8 errors                                       
                      1    09    9 errors                                       
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5923-5927          SDST: Latency 1, trial 4 (sec)           See note    
      CNP4LAT1     5092    -25.8-099.9                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5928-5932          SDST: Latency 2, trial 4 (sec)           See note    
      CNP4LAT2     5092    -88.2-087.2                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5933-5937          SDST: Latency 3, trial 4 (sec)           See note    
      CNP4LAT3     5092    -26.4-076.6                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5938-5942          SDST: Latency 4, trial 4 (sec)           See note    
      CNP4LAT4     5092    -15.7-024.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5943-5947          SDST: Latency 5, trial 4 (sec)           See note    
      CNP4LAT5     5092    -22.2-035.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5948-5952          SDST: Latency 6, trial 4 (sec)           See note    
      CNP4LAT6     5092    -32.9-030.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5953-5957          SDST: Latency 7, trial 4 (sec)           See note    
      CNP4LAT7     5092    -17.2-024.5                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5958-5962          SDST: Latency 8, trial 4 (sec)           See note    
      CNP4LAT8     5092    -28.3-034.8                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                     SYMBOL DIGIT SUBSTITUTION TEST (SDST)                      
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5963-5967          SDST: Latency 9, trial 4 (sec)           See note    
      CNP4LAT9     5092    -18.3-034.2                                          
                    570    88888 Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5968-5973          SDST: Total latency, trial 4 (sec)       See note    
      CNP4TOTL     5092    010.29-178.86                                        
                    570    888888  Blank but applicable                         
                  25649    Blank                                                
                                                                                
        5974-5975          SDST summary: Number of correct                      
      CNPCORR4             responses for latencies 2 through 9,                 
                           trial 4                                              
                      1    00                                                   
                      3    01                                                   
                      2    02                                                   
                     19    03                                                   
                     39    04                                                   
                    103    05                                                   
                    199    06                                                   
                    678    07                                                   
                   4048    08                                                   
                    570    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
        5976-5981          SDST summary: Error-corrected latency    See note    
      CNPCLAT4             for trial 4 - total latency/number of                
                           correct responses (sec)                              
                   5091    001.36-138.71                                        
                    570    888888  Blank but applicable                         
                  25650    Blank                                                
                                                                                
        5982-5986          SDST summary: Mean of the two            See note    
      CNPCBEST             lowest error-corrected latencies                     
                           (sec/correct digit)                                  
                   5077    01.38-022.2                                          
                    570    88888 Blank but applicable                           
                  25664    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       SERIAL DIGIT LEARNING TEST (SDLT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5987          SDLT: Total 0 trials                                 
      CNPT0TRA     4388    1     1 trial 0                                      
                    510    2     2 trial 0                                      
                     52    3     3 trial 0                                      
                     11    4     4 trial 0                                      
                      1    5     5 trial 0                                      
                    700    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5988          SDLT: Score, trial 1                     See note    
      CNP1SCOR      608    0     Correct                                        
                    976    1     2/3 correct                                    
                   3378    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5989          SDLT: Score, trial 2                     See note    
      CNP2SCOR     1518    0     Correct                                        
                   1098    1     2/3 correct                                    
                   2346    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  25649    Blank                                                
                                                                                
             5990          SDLT: Score, trial 3                     See note    
      CNP3SCOR     1783    0     Correct                                        
                    929    1     2/3 correct                                    
                   1748    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  26151    Blank                                                
                                                                                
             5991          SDLT: Score, trial 4                     See note    
      CNP4SCOR     1465    0     Correct                                        
                    795    1     2/3 correct                                    
                   1325    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  27026    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       SERIAL DIGIT LEARNING TEST (SDLT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
             5992          SDLT: Score, trial 5                     See note    
      CNP5SCOR     1103    0     Correct                                        
                    620    1     2/3 correct                                    
                   1100    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  27788    Blank                                                
                                                                                
             5993          SDLT: Score, trial 6                     See note    
      CNP6SCOR      790    0     Correct                                        
                    552    1     2/3 correct                                    
                    893    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  28376    Blank                                                
                                                                                
             5994          SDLT: Score, trial 7                     See note    
      CNP7SCOR      658    0     Correct                                        
                    450    1     2/3 correct                                    
                    731    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  28772    Blank                                                
                                                                                
             5995          SDLT: Score, trial 8                     See note    
      CNP8SCOR      518    0     Correct                                        
                    396    1     2/3 correct                                    
                    618    2     Incorrect                                      
                    700    8     Blank but applicable                           
                  29079    Blank                                                
                                                                                
        5996-5997          SDLT summary: Trials to criterion                    
      CNPTSTOC      502    02                                                   
                    875    03                                                   
                    762    04                                                   
                    588    05                                                   
                    396    06                                                   
                    307    07                                                   
                   1463    08                                                   
                     69    09                                                   
                    700    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
                                                                               
                                                                                
                        NHANES III Examination Data File                        
                                                                                
    ------------------------------------------------------------------------    
                   CENTRAL NERVOUS SYSTEM FUNCTION EVALUATION                   
    ------------------------------------------------------------------------    
                       SERIAL DIGIT LEARNING TEST (SDLT)                        
    ------------------------------------------------------------------------    
    Positions            Item description                                       
    SAS name    Counts       and code                               Notes       
    ------------------------------------------------------------------------    
                                                                                
        5998-5999          SDLT summary: Total score                            
      CNPTTSCR     4962    00-16                                                
                    700    88    Blank but applicable                           
                  25649    Blank                                                
                                                                                
     NOTES                                                                     
                                                                                
                                                                                
     CNP1LAT1-CNP1LAT9, CNP2LAT1-CNP2LAT9, CNP3LAT1-CNP3LAT9,                   
     CNP4LAT1-CNP4LAT9:  Latencies for trials 1-4                               
                                                                                
          A total of five trials were conducted in the Symbol Digit             
          Substitution Test (SDST), a practice trial (not included in these     
          data) and four actual trials (trials 1-4).  The practice trial was    
          primarily for training the examinee in the test procedure.  It did    
          not accept incorrect responses, and data from the practice trial      
          are not included in this file.  If the examinee entered an            
          incorrect digit, a short beep sounded, and no digit was entered on    
          the screen; to proceed, a correct digit had to be entered.  If the    
          examinee made more than four errors during the practice trial, the    
          trial was repeated.  If the examinee made more than four errors on    
          the second attempt of the practice trial, the test was                
          discontinued, and the next test was initiated automatically.          
          Symbols and digits were paired differently on each trial.  Although   
          incorrect responses were allowed on the four actual trials, more      
          than four errors resulted in a message emphasizing the need to        
          avoid errors.                                                         
                                                                                
          These variables represent the latency to enter each of the nine       
          digits of each trial.  Incorrect responses were reported as           
          negative values.                                                      
                                                                                
                                                                                
     CNP1SCOR-CNP8SCOR: Serial Digit Learning Test (SDLT) score                 
                                                                                
          Note that to allow comparison with NES2 results from other            
          settings the scoring convention for this variable differs from        
          that usually applied to the NHANES III data, where 0 indicates        
          none or never.  Examinees received a score of 0 if all eight          
          digits were entered correctly, 1 if six or seven digits were          
          entered correctly, and 2 if fewer than six digits were entered        
          correctly.                                                            
                                                                                
                                                                                
     CNP1TOTL, CNP2TOTL, CNP3TOTL, CNP4TOTL:  Total latency, trials 1-4         
                                                                                
          CNP1TOTL represents the time elapsed on trial 1 from the time         
          the first item was answered to the time the ninth item was            
          answered.  Therefore, it does not include the latency to respond to   
          the first symbol.                                                     
                                                                                
                                                                                
     CNP2LAT1-CNP2LAT9:  Latencies for trial 2                                  
                                                                                
          See note for CNP1LAT1-CNP1LAT9.                                       
                                                                                
                                                                                
                                                                               
                                                                                
     CNP2TOTL:  Total latency, trial 2                                          
                                                                                
          See note for CNP1TOTL.                                                
                                                                                
                                                                                
     CNP3LAT1-CNP3LAT9:  Latencies for trial 3                                  
                                                                                
          See note for CNP1LAT1-CNP1LAT9.                                       
                                                                                
                                                                                
     CNP3TOTL:  Total latency, trial 3                                          
                                                                                
          See note for CNP1TOTL.                                                
                                                                                
                                                                                
     CNP4LAT1-CNP4LAT9:  Latencies for trial 4                                  
                                                                                
          See note for CNP1LAT1-CNP1LAT9.                                       
                                                                                
                                                                                
     CNP4TOTL:  Total latency, trial 4                                          
                                                                                
          See note for CNP1TOTL.                                                
                                                                                
                                                                                
     CNPCBEST:  Mean of two lowest error-corrected latencies                    
                                                                                
          This single summary measure for the SDST is the mean of the           
          error-corrected latencies (CNPCLAT1-CNPCLAT4) on the two best         
          (lowest latency) of the four trials.  The units for this summary      
          measure are "sec/correct digit."                                      
                                                                                
                                                                                
     CNPCLAT1, CNPCLAT2, CNPCLAT3, CNPCLAT4:  Error-corrected latency for       
                    trials 1-4                                                  
                                                                                
          The error-corrected latency was calculated for each of the four       
          actual trials.  It is the mean number of seconds per correct          
          digit for each trial, excluding the first item in the trial.          
                                                                                
          If the number of correct responses for latencies 2 through 9 was      
          0, CNPCLAT1 was set to missing (blank).  Otherwise,                   
          CNPCLAT1=CNP1TOTL/CNPCORR1.                                           
                                                                                
                                                                                
     CNPCLAT2:  Error-corrected latency for trial 2                             
                                                                                
          See note for CNPCLAT1.                                                
                                                                                
                                                                                
     CNPCLAT3:  Error-corrected latency for trial 3                             
                                                                                
          See note for CNPCLAT1.                                                
                                                                               
                                                                                
     CNPCLAT4:  Error-corrected latency for trial 4                             
                                                                                
          See note for CNPCLAT1.                                                
                                                                                
                                                                                
     CNPMENRT:  Mean reaction time                                              
                                                                                
          To calculate the mean reaction time, values from the first ten        
          trials (CNPRT01-CNPRT10) were excluded as well as values from other   
          trials that were greater than or equal to 750 msec or less than or    
          equal to 50 msec.  This mean may not be valid if the number of trials 
          included in the average was less than 20.                             
                                                                                
                                                                                
     CNPSDRT:  Standard deviation of the reaction time                          
                                                                                
          To calculate the standard deviation of the reaction time, values      
          from the first ten trials (CNPRT01-CNPRT10) were excluded as well     
          as values from other trials that were greater than or equal to 750    
          msec or less than or equal to 50 msec.  This statistic may not be     
          valid if the number of trials included in the calculation was less    
          than 20.