F AA-AM-72-19 

RESIDUAL PERFORMANCE EFFECTS OF SIMULATED 

SONIC BOOMS INTRODUCED DURING SLEEP 

W. Dean Chiles, Ph.D. 

Georgetta West, B.S. 

FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma 73125 

May 1972 

Availability is unlimited. Document may be released 

to the National Technical Information Service, 

Springfield, Virginia 22151, for sale to the public. 

Prepared for 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

Office of Aviation Medicine 

Washington, D.C. 20591 
Federal Aviation Administration, Office of Aviation 

Medicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. RESIDUAL PERFORMANCE EFFECTS OF SIMULATED SONIC BOOMS INTRODUCED DURING SLEEP by W. Dean Chiles and 

Georgetta West, May 1972, 8 pp. Report No. FAAAM-72-19. 

Twenty-four male subjects were tested on a complex performance device involving monitoring, mental arithmetic, and 

pattern discrimination. Three age-groups were used : 21 to 

26, 40 to 45, and 60 to 72. Subjects were tested for 30 minutes 

each morning and each evening for a 21-day period. On the 

sixth through the 17th nights, subjects were exposed to eight 

simulated sonic booms with an "outdoors" overpressure level 

of 1.0 psf presented at 1-hour intervals during sleep. 

The results provided no evidence that exposure to simulated 

sonic booms during sleep produced measurable consequences 

with respect to complex performance. A significant age 

effect was found for five of the ten measures. Significant 

differences (apparently a learning effect) were found in performance across the three phases (pre-boom, boom, and postboom). There was also a significant interaction between age 

and phase for five of the measures. Analysis of the simple 

effects indicated there were rather large differences among 

the three groups at the beginning of testing with the differences decreasing in the two latter phases. 

The time-of-day effect was significant for five of the measures. 

I. Chiles, W. D. 

II. West, 

Georgetta 

Descriptors 

Complex 

Performance 

Sonic Booms 

Age 

Diurnal 

Variations 

Federal Aviation Adm

Medicine, Civil Aero

City, Oklahoma. RES

FECTS OF SIMULAT

DUCED DURING SL

Georgetta West, May 

AM-72-19. 

Twenty-four male s

formance device invol

pattern discrimination

26, 40 to 45, and 60 to 

each morning and eac

sixth through the 17th 

simulated sonic booms 

of 1.0 psf presented a

The results provided 

sonic booms during s

with respect to com

effect was found for 

differences (apparentl

formance across the t

boom). There was al

and phase for five of 

effects indicated there 

the three groups at t

ences decreasing in the 

The time-of-day effe

ures. 
Federal Aviation Administration, Office of Aviation 

l\Iedicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. RESIDUAL PERFORMANCE EFFECTS OF SIMULATED SONIC BOOMS INTRODUCED DURING SLEEP by W. Dean Chiles and Georgetta West, May 1972, 8 pp. Report No. FAAAM- 72-19. 

Twenty-four male subjects were tested on a complex performance device involving monitoring, mental arithmetic, and 

pattern discrimination. Three age-groups were used: 21 to 

26, 40 to 45, and 60 to 72. Subjects were tested for 30 minutes 

each morning and each evening for a 21-day period. On the 

sixth through the 17th nights, subjects were exposed to eight 

simulated sonic booms with an "outdoors" overpressure level 

of 1.0 psf presented at 1-hour intervals during sleep. 

The results provided no evidence that exposure to simulated 

sonic booms during sleep produced measurable consequences 

with respect to complex performance. A significant age 

effect was found for five of the ten measures. Significant 

differences (apparently a learning effect) were found in performance across the three phases (pre-boom, boom, and postboom). There was also a significant interaction between age 

and phase for five of the measures. Analysis of the simple 

effects indicated there were rather large differences among 

the three groups at the beginning of testing with the differences decreasing in the two latter phases. 

The time-of-day effect was significant for five of the measures. 

I. Chiles, W. D. 

II. West, 

Georgetta 

Descriptors 

Complex 

Performance 

Sonic Booms 

Age 

Diurnal 

Variations 

Federal Aviation Admin

Medicine, Civil Aerom

City, Oklahoma. RESID

FECTS OF SIMULATE

DUCED DURING SLE

Georgetta West, May 19

AM-72-19. 

Twenty-four male sub

formance deYice involvin

pattern discrimination. 

26, 40 to 45, and 60 to 72

each morning and each 

sixth through the 17th n

simulated sonic booms w

of 1.0 psf presented at 

The results provided n

sonic booms during slee

with respect to compl

effect was found for fi

differences (apparently 

formance across the thr

boom). There was also 

and phase for five of th

effects indicated there 

the three groups at the 

ences decreasing in the tw

The time-of-day effect 

ures. 
1. Report No. '2. Government Accession No. 3. Recipient's Catalog No. 

FAA-AM-72-19 4. Title and Subtitle 5. Report Dote 

RESIDUAL PERFORMANCE EFFECTS OF SIMULATED 

SONIC BOOMS INTRODUCED DURING SLEEP 

May 1972 

6. Performing Organization Code 

7. Author( s) 

W. Dean Chiles, Ph.D. 

Geor~etta West B.S. 9. Performing Organization Name and Address 

FAA Civil Aeromedical Institute 

P. 0. Box 25082 

Oklahoma City, Oklahoma 73125 

12. Sponsoring Agency Nome and Addresc 

Office of Aviation Medicine 

Federal Aviation Administration 

800 Independence Avenue, S.W. 

Washington, D. C. 20591 

15. Supplementary Notes 

8 . Performing Orgoni zation Report No. 

10 . Work Unit No. 

11 . Contract or Grant No. 

--------j 13. Type of Report and Period Covered 

OAM Report 

14. Sponsoring Agency Code 

This research was performed under Tasks AM-A-70-PSY-13, AM-A-71-PSY-13, 

AM-B-70-PSY-24, and AM-B-71-PSY-24. 

16. Abstract 

Twenty-four male subjects were tested on a complex performance device 

involving monitoring, mental arithmetic, and pattern discrimination. Three 

age-groups were used: 20 to 26, 40 to 45, and 60 to 72. Subjects were 

tested for 30 minutes each morning and each evening for a 21-day period. 

On the sixth through the 17th nights, subjects were exposed to eight 

simulated sonic booms with an "outdoors" overpressure level of 1.0 psf 

presented at 1-hour intervals during sleep. 

The results provided no evidence that exposure to simulated sonic booms 

during sleep produced measurable consequences with respect to complex performance. A significant age effect was found for five of the ten measures. 

Significant differences (apparently a learning effect) were found in performance across the three phases (pre-boom, boom, and post-boom). There was 

also a significant interaction between age and phase for five of the measures. 

Analysis of the simple effects indicated there were rather large differences 

among the three groups at the beginning of testing with the differences 

decreasing in the two latter phases. 

The time-of-day effect was significant for five of the measures. 

17. K0y Words 

Complex Performance 

Sonic Booms 

Age 

Diurnal Variations 

19. Security Clossif. {of this report) 

Unclassified 

Form DOT F 1100;7 1e-s91 

18. Distribution Statement 

Availability is unlimited. Document may 

be released to the National Technical 

Information Service, Springfield, Virginia 

22151, for sale to the public. 

20. Security Classif. {of this page) 21. No. of Pages 22. Price 

Unclassified 8 $3.00 
ACKNOWLEDGMENT 

The present study was conducted as a part of a larger experiment directed by Drs. W. E. Collins and P. F. Iampietro. Their complete cooperation is gratefully acknowledged. 
RESIDUAL PERFORMANCE EFFECTS OF SIMULATED SONIC BOOMS 

INTRODUCED DURING SLEEP 

I. Introduction. 

In June 1968, the Subcommittee on Human 

R~ponse, a pa_rt o£ the National Academy o£ 

Sciences Commrttee on SST -Sonic Boom, issued 

a Report on Human Response to the Sonic Boom. 

In that report, the Subcommittee posed two 

questions which, among others relating to sonic 

booms, have not yet been "fully studied." One 

o£ these questions was: "Do repeated booms 

cause changes in the depth o£ sleep as judged by 

the electroencephalogram (EEG) ?" A second 

question was: "Do repeated brief awakeninrrs o£ 

norma~ subj~cts cause behavioral changes, o psychological drs tress, or excessi Ye fatigue~" The 

prese~t study w~s conducted as a part o£ a larger 

expenment carried out by the Civil Aeromedical 

Institute to provide information bearino- on these . b 

two questwns. 

The rationale for studying sleep effects o£ 

sonic booms derives from the fact that a sirrnifi- . b 

cant portwn o£ the population sleeps at times 

other than during the nighttime hours. Thus, 

the occurrence o£ sonic booms over populated 

areas at almost any time durino- the day or nio-ht . b b 

mrght be expected to impinge upon sleepino- indi_viduals. During daylight hours, these p:ople 

mr~ht be, for example, night workers, hospital 

patients, or the elderly. The specific aspect o£ 

the problem that is o£ concern to this report is 

the possibility that, i£ there are disturbinrr effects 

o£ sonic booms on sleep, the accumulation°o£ such 

effects over a number o£ days might result in 

measurable changes in behavior. (Other aspects 

o£ the larger study will be reported in later 

OAM ~eports: Collins and Iampietro ( 1972), 

and Smith and Hutto ( 1972).) 

Previous research on the effects o£ sleep loss 

suggests that complex performance involving 

Assistance in data collection by Blair Fennell, Cynthia 

Mitchell, Karen Lewis and RuthAnn Parvin is gratefully aclmowledged. 

1 

time sharing may provide more sensitive indices 

o£ performance deficiencies than are afforded bv 

simpler measures (Chiles, Alluisi, and Adam~, 1968). In addition, the context in which this 

study was formulated placed emphasis on the 

generation o£ data and findings o£ potential 

relevance to practical situations. This consider~tion also points toward the advisability o£ 

usmg complex performance in that such performance is typical o£ the demands placed on the 

worker by his job. The CAMI Multiple Task 

Performance Battery (MTPB) provides measures o£ such performance. In addition to the 

fact that the system is largely automated and 

can be used to test up to five subjects simultaneously, the MTPB permits variations in the 

difficulty o£ individual tasks over a fair range, 

and, more importantly, the requirement for the 

time-shared performance o£ different tasks can 

be imposed. 

The above-referenced research on sleep loss 

also showed that differences in the levels o£ performance o£ even highly trained subjects can be 

expected as a function o£ time o£ day, with per-

~ormance in the evening being superior to that 

m the morning. Thus, it is possible that any 

accumulative effects o£ the sleep disturbance 

might be more readily revealed when performance is already at a lower point on the continuum. Therefore, measurement periods in both 

morning and evening hours were deemed necessary. Although a third, mid-day session would 

have been desirable, the logistics o£ testinrr sub- • b 

Jects who held regular jobs militated arrainst 

such additional testing. 0 

One o£ the facets o£ the problem identified by 

t~1e Subcommittee concerned the widely held belle£ that there are important differences across 

age-groups in the average quality o£ sleep · the 

implication was that middle and older 'arre- o 

~roups generally experience more difficulty sleepmg and are more susceptible to arousal by 
an investigation. 

The purpose of the study, then, was to examine 

complex performance as it might be affected by 

the introduction of sonic booms during sleep. 

Other factors considered in the research design 

concerned the time of day at which measures 

were to be made, the age of the subjects, and the 

specific tasks and task combinations to be performed. 

II. Method. 

A. Sttbjects. Twenty-four male subjects were 

tested in this study; they were paid for their 

services. The subjects were selected to provide 

three different age-groups. The youngest agegroup consisted of eight subjects ranging from 

21-26 years of age; their median education level 

was two years of college. The middle age-group 

contained eight subjects with an age range of 

40-45 years; their median education level was 

three years of college. The oldest age-group 

ranged from 60-72 years of age with a median 

education level of 2.5 years of college. 

B. Experimental Tas!.·s. The Multiple Task 

Performance Battery used in this study has been 

described in detail in an earlier report (Chiles, 

Alluisi, and Adams, 1968) and, therefore, will 

not be fully described here. The apparatus presented two passive and two .active tasks. The 

passive tasks consisted of monitoring warning 

lights and probability meters; the active tasks 

consisted of mental arithmetic and pattern 

discrimination. 

There were two different aspects of the warning lights task. The subjects were to monitor 

five normally illuminated green lights which 

were located one in each corner of the panel and 

one in the center. If any one of these lights 

were to go out, the subject was to push a button 

directly below that light to turn it back on. A 

red light, which was normally not illuminated, 

was paired with each of the green lights. If one 

of these lights were to come on, the subject was 

to push the button directly below that light to 

turn it off. If no response was made to a warning-light signal, the light automatically returned 

to its normal state after 15 seconds. The mean 

inter-signal interval for the warning-lights task 

was 30 seconds. Response time was measured 

2 

of two 15-minute test intervals was treat

separately. 

The second passive task involved monitori

four meters located across the top of the pan

The pointer of each meter fluctuated in a rando

manner about the zero (12 o'clock) position. 

signal on this task consisted of a shift of t

pointer of one of the meters from an avera

position of zero to an average position of pl

or minus 25 ( 1 o'clock or 11 o'clock). The su

ject responded by pushing a lever switch i

mediately below the appropriate meter in t

direction of the deflection thereby returning t

pointer to its normal state. If no response w

made, the signal would remain until the ne

signal was introduced. The mean intersign

interval on the probability task was 30 second

The performance measure was the mean corre

response time for each 15-minute interval; 

case no response was made to a given signal, t

response time was determined by the total laps

time until a response was made to a subseque

signal. 

For the two youngest age-groups, the men

arithmetic task required the subject to sol

problems by adding two 2-digit numbers a

subtracting a third 2-digit number from the 

sultant sum, e.g., 55+28-49. The subject 

corded his answer by actuation of a set of pu

buttons located above the panel; he then push

a lever switch located to the right of the arit

metic display to "set his answer into the m

chine." The problems ''ere presented at a ra

of one every 20 seconds. The performan

measures on this task were the mean respon

time and the mean percentage correct. For t

oldest age-group, the individual problem e

ments were 1-digit rather than 2-digit numbe

e.g., 8 + 7- 6. The reason for this change w

the apparent inability of one of the first tw

subjects trained in the oldest age-group to mas

the 2-digit problems. 

The problems on the pattern discriminati

task involved the successive presentation of 

standard pattern for five seconds and two co

parison patterns for two seconds each. The

patterns were presented on a 36-cell, square d

play in the lower left corner of the panel. Ea

pattern consisted of six vertical bars, rangi

in height from one to six squares. The subj
ppy 

standard pattern. The subject responded to this 

task by pushing one of three buttons marked 

"1," "2," and "N" (neither). 

The task was complicated for the subjects in 

the youngest and the middle age-group by introducing random distortions of the comparison 

images (see Chiles, Alluisi, and Adams, 1968, 

p. 156). The distortion invo~ ved four randomly 

selected "noise" cells; if a noise cell should have 

been illuminated as part of a comparison pattern, the light would :fail to come on and vice 

versa. The oldest age-group was tested without 

the distortion; it was feared that difficulties 

similar to those experienced with arithmetic 

might be encountered on this task if it were 

made too complex. Problems were presented at 

the rate of one every 30 seconds. Performance 

was measured in terms of the percentage of 

correct responses. 

C. Procedure. The subjects were trained and 

tested in two-man teams. each member of a team 

being from the same age-group. Each team was 

given a 1-hour training session, usually, the day 

before their first actual test session. The first 

30 minutes of training involved familiarizing the 

subjects with the various tasks and the appropriate responses. Each man was urged to do his 

g, jp

test session that was the same as those given 

during the test proper. The first 15 minutes 

consisted of monitoring and mental arithmetic 

and the last 15 minutes consisted of monitoring 

and pattern discrimination. Thereafter; each 

group was tested for 30 minutes each morning 

at approximately 0700 hours and 30 minutes each 

evening at approximately 2000 hours for a 21-

day period. The data collected during the first 

two days (four test sessions) were not used in 

the statistical analysis. This was considered a 

le,·eling-off period for the subjects. 

The subjects spent the first five nights (Phase 

I) sleeping in the boom room and getting adjusted to the experimental situation. For the 

next 12 consecutive nights (Phase II), eight 

simulated sonic booms were presented each night. 

They· were presented hourly beginning at 2300 

hours and ending at 0600 hours. The "outside" 

o,·erpressure le,·el of the booms was 1 psf (measured in the pressure chamber adjacent to the 

subject's sleeping quarters) and 0.1 psf inside 

the sleeping quarters. Rise time of the boom 

recorded in the sleeping quarters was 12 msecs 

with a boom duration of approximately 284 

msecs. The last four nights (Phase III) were 

set aside for a recovery period. Between the 

TABLE I.-F Ratios for Analyses of Variance 

A 

(Morn vs Even) 

d.f.=1,21 

B 

(Pre-Boom-Post) 

d.f.=2,42 

c 

(Age-Groups) 

d.f.=2, 21 

AB 

d.f.=2,42 

AC 

d.f.=2, 21 

BC 

d.f.=4,42 

ABC 

d.f.=4, 42 

*p <.05 **p <. 01 

RO R15 GO G15 MO M15 A% AT T% Comp 

7.78* .01 5. 69* 1. 58 . 01 .07 8.46* 8.01* 3.17 4.82* 

3.51* .89 13.43***28.44*** 3.83* 2.91 9.40***39.68***31.80***19.18*** 

4.21* 2.69 13.23** 9.58** .03 . 24 . 26 . 66 7.74** 4.06* 

.00 . 00 .00 .00 .00 .03 .00 .00 .00 .00 

.39 . 69 1. 53 1. 10 2.05 2.30 5.08* 1. 04 . 80 2.25 

3.17* 6.48*** 4.02** 14.54*** 1. 10 .75 1. 54 1. 96 . 45 8.34*** 

.00 . 00 .00 .GO . 00 .03 .00 .00 . 00 .00 

***p <. 001 

3 
of the subjects in the youngest age-group were 

students and three had regular jobs. Seven of 

the subjects in the middle age-group were employed in various occupations and one was a 

student. Seven of the subjects in the oldest agegroup were retired and one had a professional 

job. 

III. Results. 

Each of the nine performance measures and a 

composite measure of monitoring performance 

were subjected to analyses of variance (Lindquist Type VI design). The monitoring. composite was the sum of the linear transformation 

of the red-lights measures, green-lights measures, 

and meter measures; for this composite measure, 

a larger number reflects better performance. 

The variables entered in each analysis were: 

experiment phases (Phase I, pre-boom; Phase 

II, boom ; and Phase III, post-boom) , agegroups (the youngest-21-26 year olds, the 

middle age-group--40-45 year olds, and the 

oldest group-60-72 year olds), time of day 

(morning and evening), and subjects (within 

groups). The results of these analyses are sho,vn 

in Table 1. 

A. 0 omposite J,f onitming llf easure. Analysis 

of this measure revealed a significant difference 

in performance across phases and a significant 

difference between the performances of the different age-groups along with a significant interaction between the two variables (Table 1). The 

cell means for this interaction are shown in 

Table 2. The data were further evaluated by 

"t" tests (as outlined by Lindquist ( 1956, p. 

272)) between individual means to clarify the 

effects of the two variables involved. The oldest 

age-group's performance improved significantly 

in comparing Phase II with Phase I (t=3.78, 

d.f.=42; p<.01) and likewise in comparing 

Phase III with Phase I (t=5.41, d.£.=42; 

p<.01). The other two groups showed no such 

improvement. In comparing groups, the oldest 

age-group performed significantly poorer than 

the youngest (t=3.81; p<.05) and middle agegroup (t=2.51; p<.01) only during the first 

phase of testing. 

Performance for this measure was significantly 

better in the evening than in the morning (Table 

3). 

4 

Age 

20 40 60 

RArith I 1. 08 1. 36 2.15 

II 1. 02 1. 32 1. 79 

III 1. 12 1. 37 1. 74 

RTID I 1. 05 1. 44 1. 86 

II 1. 04 1. 60 1. 49 

III 1. 23 1. 53 1. 37 

GArith I 2.31 3. 75 5.97 

II 2. 12 3.28 4.94 

III 2.23 3.05 4.34 

GTID I 2.16 3.53 5.81 

II 1. 89 3.23 4.14 

III 2.13 3.02 3.49 

MArith I 13.71 10.20 12.68 

II 8.26 11.77 10.49 

III 8.59 7.36 9.04 

MTID I 10.50 12.69 12.52 

II 8.00 15.59 10.54 

III 7.61 8.81 7.78 

A% I 86.04 91.20 90.40 

II 95.43 94.77 91.81 

III 95.97 95.94 93.70 

A Time I 7.96 9.01 8.12 

II 7.64 8.11 7.64 

III 7.13 7.62 7.35 

T% I 80.08 79.37 91.56 

II 88.09 85. 13 96.69 

III 87.83 85.47 97.67 

Comp. I 40.46 37.90 32.95 

II 41.72 37.83 36.26 

III 40.94 39. 16 37.68 

TABLE 3.-Means for Measures that Showed a Significan

Time-of-Day Effect. 

Morning Evening 

RArith 1. 48 1. 40 

GArith 3.69 3.42 

A Time 7.99 7.70 

Comp. Score 38.10 38.55 

p <. 05 for the difference between morning and evenin

for each measure. 

B. Red-Lights Afeasures. The red-lights meas

ures for the first 15-minute test interval showe

significant differences ln performance acros
no such differences. Ho"·eyer, both measures 

showed a significant interaction between experiment phase and age as seen in the cell means for 

those measures in Table 2. Further analysis 

showed that the performance of the oldest agegroup improYed significantly from Phase I to 

Phase II during the first interval (t=2.42, 

d.f.=42; p<.05) and likewise for the second 

interval (t=2.42, d.f.=42; p<.05). Performance also improYed from Phase I to Phase III 

for the first interval (t=2.76, d.f.=42; p<.01) 

and for the second interval ( t = 3.20, d.f~= 42; 

p<.01). Neither of the other groups showed 

significant changes across phases. During Phase 

I, the youngest age-group performed significantly better than the oldest for the first-interval 

(t=3.67; 7J<.05) and the second-interval (t= 

3.42; p<.05) measures. The middle age-group 

responded significantly faster to the red lights 

than did the oldest age-group during Phase I 

for the first 15-minute intenal (t=2.64; p<.05). 

For Phase II, only the first-interval measure 

showed significant differences between groups; 

the youngest age-group responded more quickly 

than the oldest (t=2.57; p<.05). 

Both measures showed better performance in 

the evening than in the morning, but the difference was significant only for the first-interval 

measure (Table 3). 

C. Green-Lights Measttres. Both green-lights 

measures showed significant differences across 

phases and between groups, and there was a 

significant interaction between the two variables 

(Table 1). Analysis of the simple effects (cell 

means for those measures in Table 2) showed 

that the performance of the oldest age-group 

improved significantly from Phase I to Phase II 

for the first-interval measure ( t=2.63, d. f. =42; 

p<.01) and also for the second-intern! measure 

(t=5.14, d.f.=42; p<.01). The improvement 

of the oldest age-group from Phase I to Phase 

III was also significant for the first-intenal 

measure (t=4.16, d.f.=42; p<.01) and the 

second-intenal measure (t=7.14, d.f. = 42; 

p < .01). No other groups showed significant 

imprm·ement across phases. For the measures 

during both intervals, a significant difference 

across age-groups was found during all three 

phases. The largest differences behYeen groups 

were found during Phase I. For the first 15-

5 

the middle age-group ( t = 2.38; p < .05) and the 

oldest age-group (t=6.06; p<.05); and the 

middle age-group responded significantly faster 

than the oldest age-group (t=3.68; p<.05). 

During the second 15-minute interval, the responses of the youngest age-group were significantly faster than those of the middle age-group 

(t=2.35; p<.05) and the oldest age-group 

(t=6.25; p<.05) and, as with the first-interval 

measure, the middle age-group responded significantly faster than the oldest age-group 

(t=3.91; p<.05). During Phase II, the firstinterval measure showed significant differences 

between the middle and the oldest age-groups 

(t=2.75; p<.05) and between the youngest and 

oldest age-groups (t=4.67; p<.05) with the 

oldest age-group having the poorer performance 

in each case. The second-interval measure 

showed significant differences between the youngest and the middle age-groups (t=2.30; p<.05) 

and between the youngest and the oldest agegroups ( t = 3.85; p < .05) with the youngest agegroup having the better performance in each 

case. During Phase III, the youngest age-group 

performed significantly better than the oldest 

age-group for both the first 15-minute interval 

(t=3.49; p<.05) and the second interval (t= 

2.33; p<.05); and the middle age-group performed significantly better than the oldest agegroup on the first-interval measure ( t=2.14; 

p<.05). 

As with the red lights, both green-lights 

measures showed better performance during the 

e\·ening but only with the first-interval measure 

was the difference between morning and evening 

performance significant (Table 3). 

D. Probability lffonit01ing. None of the variables had a significant effect on the secondinterval probability measure. The only significant effect on the first-interval measure was a 

significant difference across phases (Table 1). 

The performance of the groups during Phase I 

was significantly poorer than their Phase-III 

performance (Table 2). As seen in Table 2, 

although the age by phase interaction was not 

significant, only the oldest age-group showed 

continuous improYement across phases. 

E. Arithmetic lf!easures. Neither arithmetic 

measure sho"·ed significant differences between 
gp,

Phase I to Phase II (t=6.fl6, d.f.=42; p<.01) 

and from Phase I to Phase III (t=8.20, d.f.=42; 

p< .01) . Since there was a significant interaction behYeen time of day and age-groups, fnrther 

analyses were performed. No differences were 

found between groups for either morning or 

e,-ening sessions; and only the oldest age-group 

performed significantly better in the evening 

than in the morning on this task (Table 4) . For 

the arithmetic response-time measure, Phase I 

performance was significantly poorer than that 

of Phase II (t=10.16, d.f.=42; p<.01) or Phase 

III (t=17.82, d.f.=42; p<.01); and Phase II 

performance was significantly poorer than that 

of Phase III (t=7.66, d.f.=42; p<.01). 

The response times of the subjects in the evening were significantly faster than for morning 

performance (Table 3). 

TABLE 4.-Cell Means for Arithmetic Percentage 

(Age and Time-of-Day Interaction). 

Morning ______ _ 

Evening ______ _ 

20 

92.74 

92.23 

Age 

40 

93.11 

94.85 

60 

89.36 

94.59 

F. PatteT1t Discrimination. As shown in 

Table 1, the oldest age-group (which was presented problems without distortion of the comparison patterns) performed significantly better 

than both the youngest age-group (t=3.06, 

d.£.= 21; p<.01) and the middle age-group 

(t=3.67, d.f.=21; p<.01). Performance on this 

task improved from Phase I to Phase II 

(t=6.71, d.f.=42; p<.05) and from Phase I to 

Phase III (t=7.08, d.f.=42; p<.05). 

IV. Discussion. 

The mechanism through which the sonic 

booms might haYe been expected to produce performance decrements would presumably have 

been a reduction in the amount of sleep and/ or 

a deterioration in the "quality" of sleep dnring 

Phase II. This would have been expected to be 

re\'ealed in the form of decrements during Phase 

II relatiYe to Phase III; and, on the assumption 

that learning was complete before the beginning 

6 

\p

, 

data reflecting the main effect of phases loo

very much like a learning effect. There we

no decrements dnring Phase II relative to eith

the pre- or post-boom phases. Thus, there is n

evidence that any possible sleep interferenc

produced by the simulated sonic booms of 1 p

(0.1 psf inside the sleeping quarters) had 

residual effect on the performance of any of th

age-groups. The lack of a performance effe

of the booms is clearly compatible with the r

sults of the analyses of the sleep behavior of th

subjects. Namely, the results of those analyse

indicated that, on the average, sleep during th

boom phase of the experiment did not diffe

from that during the preceding or succeedin

phases (Collins and Iampietro, 1972). 

Despite the fact that the experimental desig

did not provide a very powerful test of th

effects of age as a variable, significant difference

between age-groups were found. The primar

reason for the relatively low power of the desig

was that, although eight subjects per group gav

adequate power for assessing the effects of th

boom, this was a rather small number for th

main effect of age. In addition, the apparen

necessity of giving easier problems to the oldes

subjects on the arithmetic and pattern discrimi

nation tasks would be expected to attenuate an

real differences between that group and the othe

two groups. Clearly, the differences in problem 

difficulty would be expected to have direct effect

on the performance of the arithmetic and pat

tern discrimination tasks, and, because of th

time sharing requirements, we might expect in

direct effects on the performance of the othe

~asks. Thus, the significant differences acros

age-groups on the pattern discrimination task 

are properly attributed to the fact that the old

est age-group had easier problems. It could be 

argued that the lack of a significant age effec

on the arithmetic task is, in fact, evidence tha

there was an age effect. Specifically, as regards 

the percentage-correct measure, the 1-digit problems were so easy that, if age were not a factor

the oldest age-group should have performed significantly better than the other two groups, but 

they actually performed (non-significantly) 

poorer. The argument is even clearer in the 

case of the response-time measure. In another 

study using the same tasks with college-age sub-
seconds for the same 1

digit problems after only 

two 15-minute practice sessions (Jennings, Chiles, 

and \Vest, 1972). However, direct substantiating 

evidence for these arguments is not available, 

and, therefore, they must be regarded as inferences. 

The most prominent age effect was observed 

in the prolongation of the learning process in the 

oldest age-group as compared to the other two 

age-groups in the performance of the warninglights monitoring task. The general picture 

presented by these measures was that of rather 

large differences in response times between the 

oldest and the other age-groups during Phase I, 

with reductions in the magnitudes of the differences in Phase II and III. More direct evidence 

of the slower learning rate of the oldest agegroup is seen in the interaction between agegroups and phases on the monitoring tasks. 

Specifically, significant improvements across 

phases were found only in the case of the oldest 

age-group. The pattern of significant differences 

between the middle and youngest age-groups, 

e.g., differences in Phase I and Phase II but not 

in Phase III, is suggestive of a difference in the 

learning rates of those two groups. The finding 

of differential learning rates, which is clearest 

in the comparison of the oldest and the youngest 

age-groups, is directly compatible with previous 

findings such as those of Welford and Birren 

(1965) who reported age-related impairments in 

ability to learn simple tasks. 

There appear to be three mechanisms underlying the differences in age-groups. The three 

possibilities are clearly not mutually exclusive 

and it is quite likely that all contributed. First, 

the differences could have been a repetition of 

the findings of previous reaction time studies 

though only in part. For example, the largest 

difference found by Goldfarb (1941) between a 

group ranging in age from 18 to 24 and a group 

ranging in age from 55 to 64 was with a 5-choice 

reaction time task; the actual magnitude of the 

difference was less than 0.1 seconds. If we use 

this figure as an estimate of the contribution of 

reaction time to the difference between our 

youngest and oldest subjects, then reaction time 

would account for less than 20% of the difference in the case of red-lights monitoring (with 

arithmetic) and less than 5% in the case of green 

lights (also with arithmetic). The second likely 

7 

Clearly, the rate at which the subject could 

effectively scan the various monitoring displays 

and the frequency with which he did so would 

be important determiners of response times. 

This would be especially true of the green lights 

as compared to the red lights in that the onset 

of a red light was much more likely to be seen 

"out of the corner of the subject's eye." Another 

aspect of the efficiency of scanning is the flexibility of the subject in shifting, for example, 

from working an arithmetic problem to scanning the monitoring displays. Closely related 

to the flexibility factor is the breadth of the 

subject's attention with respect to perceiving a 

monitoring signal when his vision is focused on 

the displays for one of the two active tasks. 

The findings reported by Wall ace ( 1956) lend 

support to the proposition that flexibility and/or 

breadth of attention were important contributors. He found that subjects in their sixties 

required tachistoscopic exposures about six times 

as long as did those in their twenties in the 

identification of very simple pictures and designs; they required up to 20 times as long for 

more complicated material. The third possible 

contributor to the production of performance 

differences as a function of age is differential 

motivation. However, the observations of the 

experimenters gave them the clear impression 

that the oldest age-group took the experiment 

the most seriously; the middle age-group was 

next; and the youngest subjects, although their 

continued application to the tasks was above our 

expectations, took the experiment the least 

seriously. Since the apparent differences in 

motivation were most pronounced toward the 

end of Phase III, any bias present should have 

tended to favor the performance of the older 

age-groups and, thus, would tend to underestimate age effects. Therefore, we consider the 

best explanation of the results with respect to 

age to be that the biggest contribution was made 

by differences in time-sharing skills such as scanning habits and flexibility of attention. Reaction time per se undoubtedly made a contribution, but it was probably relatively small. 

The obtained differences between morning and 

evening performance are clearly compatible with 

the findings of previons research reviewed by 

Ray, ~fartin , and Alluisi ( 1961) and Trumbul 

( 1966) as well as the research reported by Chiles, 
gpg 

that the multiple task performance approach 

used in this study yields relatively sensitive 

measures. Generally, we would not consider 

time of day to be one of the more powerful laboratory variables. It should also be remembered 

that the difference favoring evening performance 

was present despite the fact that a full day of 

activity intervened between the morning and 

evening sessions. On the other hand, an average 

time of only about 30 minutes elapsed from the 

time the subjects were aroused from sleep until 

they reported to the laboratory for testing. 

Thus, the pace of events p~ior to the morning 

test session may have been rather slow with 

respect to bringing them to a full level of performance alertness. The obtained interaction 

between time of day and age-group in the case 

of the percentage-correct arithmetic measure, 

when analyzed for simple effects, suggests that 

the oldest age-group may have had more difficulty "getting up to speed" in the morning than 

did the youngest age-group. However, this was 

the only measure that yielded a significant _interaction between these two variables. Therefore, 

this finding should probably be considered as an 

isolated case since we can offer no good rationale 

as to why the effect should be peculiar to the 

accuracy of arithmetic computation. 

The simulated sonic booms introduced durin

sleep did not have measurable consequences wit

respect to complex performance. The fact tha

significant effects were found as a function o

age and as a function of the time of day at whic

performance was measured suggests that th

measures were sensitive to meaningful variable

Thus, it is concluded that the sleep effects of th

booms did not contribute significant varianc

with respect to performance. 

Age appears to make a large contribution t

the level of complex performance to be expecte

under these conditions. The most prominen

feature is the difference in the rate at whic

skill is acquired, but, even after extensive prac

tice, differences between the oldest subjects ( 6

to 72) and youngest subjects (21 to 26) are sti

evident. Earlier in learning, significant differ

ences are also seen between middle age-grou

subjects ( 40 to 45) and the oldest subjects. And

at the beginning of learning, differences are see

between the youngest and middle age-grou

subjects. 

The time of day at which testing is carrie

out was found to be a significant contributor t

the level of performance exhibited by the sub

jects. Thus, further support is given to th

generally held conclusion that diurnal variation

in performance must be considered both as 

part' of the methodology of performance meas

urement and in establishing operating proce

dures. 

REFERENCES 

1. Chiles, W. D., E. A. Alluisi, and 0. S. Adams: Work 

Schedules and Performance During Confinement, 

HUMAN FACTORS, 10:143-196, 1968. 

2. Collins, W. E., and P. F. Iampietro: In preparation 

for OAM publication, 1972. 

3 Goldfarb, W. : An Investigation of Reaction Time 

in Older Adults and Its Relationship to Certain 

Observed Mental Test Patterns. Teachers College 

Contribution to Education, No. 831, New York, 

Columbia University, 1941. 

4. Jennings, Alan E., W. D. Chiles, and Georgetta 

West: l\fethoclology in the measurement of complex 

human performance: Two dimensional compensatory 

tracking. Office of Aviation :\Ieclicine Report A:\l72-21, 1972. 

5. Lindquist, E. F.: Design rznd Analysis of Experiments in Psycltology and Education, Boston, Houghton l\liffiin Company, 1956. 

8 

6. Ray, J. T., 0. E. Martin, Jr., and E. A. Alluis

Human Performance as a Function of the Work

Rest Cycle: A Review of Selected Studies, NA

NRC Publication 882, 1961. 

7. Smith, R. C., and G. Hutto: Sonic Booms and Sleep

Affect Change as a Function of Age. Office o

Aviation Medicine Report No. FAA-AM-72-24, 197

8. Trumbull, R.: Diurnal Cycles and Work-Rest Sched

uling in Unusual Environments, HUMAN FACTORS

8 :385-398, 1966. 

9. Wallace, J. G. : Some Studies of Perception in Re

lation to Age, BRITISH JOURNAL OF PSYCHOL

OGY, 47:283-297, 1956. 

10. Welford, A. T., and J . E. Bin·en (Eels.) : Behavio

Aging, and tlt c Xc1TOus System, Springfield, Illinoi

Thomas, 1965. 
Federal Aviation Administration, Office of Aviation 

Medicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. RESIDUAL PERFORMANCE EFFECTS OF SIMULATED SONIC BOOMS INTRODUCED DURING SLEEP by W. Dean Chiles and 

Georgetta West, May 1972, 8 pp. Report No. FAAAM-72-19. 

Twenty-four male subjects were tested on a complex performance device involving monitoring, mental arithmetic, and 

pattern discrimination. Three age-groups were used: 21 to 

26, 40 to 45, and 60 to 72. Suhjects were tested for 30 minutes 

each morning and each evening for a 21-day period. On the 

sixth through the 17th nights, subjects " -ere exposed to eight 

simulated sonic booms with an "outdoors" overpressure level 

of 1.0 psf presented at 1-hour intervals during sleep. 

The results provided no evidence that exposure to simulated 

sonic booms during sleep produced measurable consequences 

with respect to complex performance. A significant age 

effect was found for five of the ten measures. Significant 

differences (apparently a learning effect) were found in performance across the three phases (pre-boom, boom, and postboom). There was also a significant interaction between age 

and phase for five of the measures. Analysis of the simple 

effects indicated there were rather large differences among 

the three groups at the beginning of testing with the differences decreasing in the two latter phases. 

The time-of-day effect was significant for five of the measures. 

I. Chiles, W . D. 

II. West, 

Georgetta 

Descriptors 

Complex 

Performance 

Sonic Booms 

Age 

Diurnal 

Variations 

Federal Aviation Adm

Medicine, Civil Aero

City, Oklahoma. RES

FECTS OF SIMULAT

DUCED DURING SL

Georgetta West, May 

AM-72-19. 

Twenty-four male s

formance device invol

pattern discrimination

26, 40 to 45, and 60 to 

each morning and eac

sixth through the 17th 

simulated sonic booms 

of 1.0 psf presented a

The results provided 

sonic booms during s

with respect to com

effect was found for 

differences (apparentl

formance across the t

boom). '!.'here was al

and phase for five of 

effects indicated there 

the three groups at t

ences decreasing in the 

The time-of-day effe

ures. 
Federal Aviation Administration, Office of Aviation 

Medicine, Civil Aeromedical Insti tute, Oklahoma 

City, Oklahoma. RESIDUAL PERFORMANCE EFFECTS OF SIMULATED SONIC BOOrrS INTRODUCED DURING SLEEP by W. Den. Chiles and Georgetta -West, May 1972, 8 pp. Rep No. FAAAM-72-19. 

Twenty-four male subjects were tested on a complex performance device involving monitoring, mental arithmetic, and 

pattern discrimination. Three age-groups were used: 21 to 

26, 40 to 45, and 60 to 72. Suhjects were tested for 30 minutes 

each morning and each evening for a 21-day period. On the 

sixth through the 17th nights, subjects were exposed to eight 

simulated sonic booms with an "outdoors" overpressure level 

of 1.0 psf presented at 1-hour intervals during sleep. 

I. Chiles, W. D. 

II. West, 

Georgetta 

Descriptors 

Complex 

Performance 

Sonic Booms 

Age 

Diurnal 

Variations 

Federal Aviation Admi

Medicine, Civil Aerom

City, Oklahoma. RESI

FECTS OF SIMULATE

DUCED DURING SLE

Georgetta West, May 1

AM-72-19. 

Twenty-four male sub

formance device involvi

pattern discrimination. 

26, 40 to 45, and 60 to 7

each morning and each 

sixth through the 17th 

simulated sonic booms 

of 1.0 psf presented at 

:------------------------------- ..... ________________________ ------------------------------------------------------------------------------------------... . --

The results provided no evidence that exposure to simulated 

sonic booms during sleep produced measurable consequences 

with respect to complex performance. A significant age 

effect was found for five of the ten measures. Significant 

differences (apparently a learning effect) were found in performance across the three phases (pre-boom, boom, and postboom). There was also a significant interaction between age 

and phase for five of the measures. Analysis of the simple 

effects indicated there were rather large differences among 

the three groups at the beginning of testing with the differences decreasing in the two latter phases. 

The time-of-day effect was significant for five of the measures. 

The results provided 

sonic booms during sle

with respect to comp

effect was found for f

differences (apparently 

formance across the th

boom). There was also 

and phase for five of 

effects indicated there 

the three groups at the 

ences decreasing in the 

The time-of-day effec

ures.