AM 69-9 

EFFECTS OF TWO COMMON MEDICATIONS ON 

COMPLEX PERFORMANCE 

Approved by 

~~ J. RoBERT DILLE, M.D. 

CHIEF, CIVIL AEROMEDICAL 

INSTITUTE 

W. Dean Chiles, Ph.D. 

Harry L. Gibbons, M.D. 

Paul W. Smith, Ph.D. 

Released by 

P. v. SIEGEL, M.D. 

FEDERAL AIR SURGEON 

June 1969 

Department of Transportation 

FEDERAL AVIATION ADMINISTRATION 

Office of Aviation Medicine 
Qualified requesters may obtain Aviation Medical Reports from Defense Documentation 

Center. The general public may purchase from Clearinghouse for Federal Scientific and 

Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151. 
EFFECTS OF TWO COMMON MEDICATIONS ON COMPLEX PERFORMANCE 

I. Introduction. 

Many individuals, at the first sign of a cold, 

follow the admonishments of the TV commercials and take one of the large variety of antihistaminics available on the market. Similarly, 

lesser numbers of individuals troubled with 

stomach disorders take a variety of medications 

to alleviate symptoms. The bottle in which the 

antihistamine comes typically cautions the user 

not to drive or operate machinery in the event 

that drowsiness should occur. It is to be expected that people would observe this caution 

with various degrees of care and that different 

people would adopt different criteria as to when 

drowsiness is present. An analogous situation 

can be said to exist in the case of those gastrointestinal remedies containing barbiturates. It 

is clear that doses of these two types of medications exceeding some level would lead to decrements in the individual's performance capabilities. What is not clear is the effect, if any, of 

normal, clinical dosages. 

The purpose of this exploratory research was 

to examine the effects of normal, clinical dosages 

of Donnatal and chlorpheniramine maleate on 

the performance of complex tasks assessing important elements. of human behavior of the sort 

involved in aircraft and air traffic control operations. 

II. Method. 

Subjects. The 10 subjects who served in this 

experiment were college students who had received extensive preliminary training and experience on the battery of tasks used. They 

were trained and tested in five-man groups; the 

test apparatus provided five subject positions, and 

testing five subjects simultaneously not only 

permitted the measurement of group performance but was also both efficient and economical. 

The subjects were paid for their services at a 

rate of approximately $9 per 4-hour session. 

They were also offered a bonus of $2 for per1 

formance that "equaJled or exceeded the level" 

they had previously demonstrated themselves to 

be capable of achieving. 

Apparatus. The apparatus used in this experiment has been described in detail elsewhere* 

and, therefore, will be described only briefly 

here. The subjects performed on a battery of 

five tasks presented in six different combinations 

so that both the level and natures of the. workload imposed could be varied. The tasks are 

identified by the following names : warning lights 

monitoring, probability monitoring, arithmetic, 

code-lock (a group task), and target identification. 

The warning lights task involved the monitoring of a static process and consisted of two aspects. The first aspect was represented by five 

red lights--one at each corner and one in the 

middle of the panel. The subject was instructed 

to push the button below a given red light any 

time that light was illuminated. The second 

aspect consisted of green lights paired with the 

above-mentioned red lights. With this task, the 

subject was required to push a button below a 

given green light to re-illuminate that light if it 

should go off. For each of these two tasks, response times were measured in tenths of a second 

from the onset (or offset) of a light until the 

subject returned the light to its normal condition 

by pushing the appropriate button. 

The probability monitoring task required the 

subject to scan four, randomly fluctuating meters 

to determine if the average of the pointer positions of any meter had deviated from zero (12 

o'clock). The "signal" to which he was to respond was a shift in the mean of a given meter 

from zero to 25 units to the right or the left. If 

the subject suspected a bias to be present on a 

particular meter, he tested his hypothesis by 

throwing a three-position, spring centered lever-

* CHILEs, W. D., E. A. ALLUISI and 0. S. ADAMS : 

Work schedules and performance during confinement. 

Human F'aotors, 10:143-196, 1968. 
type switch in the direction of the sus~ted 

bias. The pointer would automatically come to 

rest on its correct mean, thus, giving him immediate feed-back as to the accuracy of his response. Time was recorded to the nearest second 

from the introduction of a bias until the appropriate response removed the bias or until that 

bias was replaced by a new bias on that or some 

other meter. 

The mental arithmetic task required the subject to sum two three-digit numbers and subtract 

a third three-digit number from that sum. He 

entered his answer by appropriate manipulation 

of a set of three decade pushbuttons for the first 

three digits and a three-position, center-off switch 

to indicate whether the fourth digit was a "O" 

or a "1." Problems were presented at a rate of 

three per minute; performance was scored in 

terms of the percentage of problems correct. 

The target identification task required the subject to view a standard "target image" and then 

decide whether the first, second, or neither of 

two comparison images was the same as the 

standard image. The task was made somewhat 

more difficult by random distortion of the comparison images. Problems were presented at a 

fixed rate of two per minute. The subject indicated his answer by depression of the appropriate 

one of three buttons marked "1", "2", and "N" 

(Neither). Performance was measured in terms 

of the number of correct responses. 

The code-lock task, which involved group performance, required the subjects to find the correct 

sequence in which each subject should push the 

code-lock button located on each subject's panel; 

entering the correct sequence illuminated a green 

light. The onset of a red light on each subject's 

panel indicated to the subject that a problem was 

present and, during the search for the correct 

sequence, provided an immediate indication that 

an error had been made. The subjects followed 

a standard search procedure until each subject 

had pushed his button once and only once in the 

correct sequence at which time the green light 

was illuminated. After a 30-second delay, the 

same problem was presented again and the subjects were to enter the previously obtained solution as rapidly as possible without error. Then, 

after another 30-second delay, a new problem 

was presented. The subjects used an earphone 

intercom system to coordinate both their initial 

search for the correct sequence and the entering 

of their second solution. Measures were made 

of the time required to reach the first solution, 

the time required to enter the second solution, 

the total number of errors, and the total number 

of responses for the first and for the second 

solutions. 

Procedure. Performance was measured during 

one session for a given day on the combinations 

of tasks shown in Table 1 ; each test session lasted 

4 hours and consisted of two of these programs 

in succession. Although no break was provided 

in the 4-hour schedule, subjects could, with permission, leave their duty stations one at a time 

for purposes of going to the rest rooms or getting 

a drink of water during the period beginning at 

105 minutes and ending at 130 minutes. 

TABLE I.-Basic 2-hour Task Performance Schedule 

Task 

00 15 30 

Reaction time _________________ XXX XXX XXX Meter monitoring ______________ XXX XXX XXX 

Mental arithmetic _____________ XXX XXX 

Problem solving _______________ XXX 

Visual discrimination ___________ 

Drug administration. The two drugs used in 

this experiment were Donnatal (phenobarbital16.2 mg.; hyoscyamine sulfate-0.1037 mg.; 

atropine sulfate-0.0194 mg.; hyoscine hydrobromide--0.0065 mg.; plus lactose) and chlorpheniramine maleate ( 4 mg.; plus lactose). The 

2 

Time (Minutes) 

45 60 75 90 105 120 

XXX XXX XXX XXX XXX 

XXX XXX XXX XXX XXX 

XXX XXX XXX 

XXX XXX 

capsules containing the drugs were identical in 

size and appearance; they were taken immediately before a given test session began. The 

experiment consisted of five sessions. The first 

session was a "no-capsule" baseline control. In 

the subsequent sessions, the capsules were admin-
istered "double blind." All subjects in a crew 

received the same drug on a given session. On 

two of the sessions, subjects were given a capsule 

containing Donnatal ; on one session they were 

given a capsule containing lactose; and on one 

session they were given chlorpheniramine maleate. 

The only information given to the subjects about 

the drugs was that on a given day, they would 

be taking a normal dosage of one of two commonly used medications. 

III. Results and Discussion. 

Friedman's analysis of variance by ranks was 

used to evaluate the differences in performance 

across the three basic drug conditions. Separate 

analyses were performed for the red lights, green 

lights, and probability monitoring tasks for each 

of the six combinations of tasks under which 

these three monitoring tasks were performed. 

Separate analyses were also performed for the 

arithmetic and target identification tasks for each 

of the two task combinations under which they 

were performed. Thus, 22 analyses were carried 

out-18 for the monitoring tasks and four for 

the active tasks. No analysis was attempted on 

the code-lock task since only group performance 

was measured on this task and, with only two 

groups of subjects being tested, no adequate estimate of error variance was available. The results of these analyses for the red, green, and 

probability monitoring tasks are shown in Tables 

2, 3, and 4 respectively. The results of the 

analyses of the arithmetic and target identification data are shown in Tables 5 and 6. 

Table 2. Red Lights Monitoring 

(Mean Response Times in Seconds) 

Task Don- Chlor. Place- X 2r 

natal Mal. bo 

Monitoring only _________ 1.17 1. 16 1. 03 1. 55 

Arithmetic _____ • 94 1. 24 1. 00 2.6 

Arithmetic & 

code-lock ____ 1.12 1. 20 1. 35 5.85 

Code-lock ______ 1. 04 1. 31 1. 16 2.45 

Target identification and 

code-lock ____ 1. 60 1. 12 . 97 11.15 

Target identification ______ 1. 29 1. 70 1. 04 6.20 

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TABLE 3. Green Lights Monitoring 

(Mean Response Times in Seconds) 

Task Don- Chlor. Place- X2r 

natal Mal. bo 

Monitoring only _________ 3.44 2.54 2.56 .05 

Arithmetic _____ 3.22 2.08 2.14 3.65 

Arithmetic and 

code-lock ____ 2.14 2.87 4.91 .05 

Code-lock ______ 2.51 3.52 2.70 2.6 

Target identification and 

code-lock ____ 3.09 5.19 2.98 .35 

Target identification ______ 3.00 4.63 2.98 1.4 

TABLE 4. Probability Monitoring 

(Mean Detection Times in Seconds) 

Task Don- Chlor. Place- X2r 

natal Mal. bo 

Monitoring only _________ 63.05 62.48 60.09 . 6 

Arithmetic _____ 70.73 68.57 65.49 1.4 

Arithmetic and 65.66 68.62 70.32 2.6 

code-lock ____ 65.66 68.62 70.32 2.6 

Code-lock ______ 67.50 74.28 68.95 2.6 

Target identification and 

code-lock ____ 67.25 74.50 72.06 .08 

Target identification ______ 67.86 78.76 74.51 3.8 

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Only two of the resultant statistics reached the 

.05 level of significance, and both of these were 

for the response times to the red lights. Response time to the onset of red lights when the 

task combination involved performance of the 

red light task concurrently with the target identification and code-lock tasks differed significantly for the three drug conditions (P is less 

than .01). The ordering of the mean times was, 

from shortest to longest, placebo, chlorpheniramine maleate,. and Donna tal. Performance of 

the red lights task also differed significantly for 

the three drug conditions (P is less than .05) 

when this task was performed in combination 

with the target identification task without concurrent code-lock performance. However, in this 
case, although the shortest response times were 

again associated with the placebo condition, the 

ordering o£ the other two drug conditions was 

reversed ; performance with Donna tal was better 

than with chlorpheniramine maleate. 

TABLE 5. Arithmetic Performance, Percent Correct 

Task Don- Chlor. Place- X2r p 

natal Mal. bo 

With code-lock_ 89.6 87.8 84.9 3.65 ------ With monitoring only _____ 91.8 91.1 92.7 2.26 ------

TABLE 6. Target Identification, Percent Correct 

Task Don- Chlor. Place- X2r p 

natal Mal. bo 

With Code-lock_ 81.3 74.0 79.0 1. 95 ------

With monitoring only _____ 87.3 85.0 85.3 1. 80 ------

Clearly the law o£ parsimony dictates that 

obtaining two significant statistics out o£ the 

total o£ 22 that were computed should properly 

be attributed to chance. This interpretation is 

reinforced by two further considerations. First, 

there is no rationale that would predict that this 

task would show an effect o£ either or both o£ 

these drugs in the absence o£ any effect on other 

tasks. Second, in previous research with the 

battery o£ tasks, the red warning lights task has 

been highly resistant to the effects o£ relevant 

variables. The £act that the ordering o£ the two 

drugs £or the two different task combinations is 

reversed also suggests that this finding is something other than a real effect o£ the drugs. 

It was recognized £rom the beginning that the 

dosages o£ the two drugs were marginal in terms 

o£ producing a measurable effect on performance. 

The rationale £or selecting these dosages was 

that the information that was needed was with 

4 

respect to the effects o£ ingestion o£ typical 

amounts o£ the drugs in question. Further, it 

was assumed that people follow instructions when 

taking such drugs, and therefore, information as 

to the effects o£ overdoses would not be particularly useful. Clearly, i£ the nature o£ these 

two drugs were less well known, this rationale 

would be less appropriate. 

Another £actor that tended to minimize the 

possible effects o£ the drugs was that the subjects were highly trained £or their "jobs." The 

subject with the least total training on the task 

complex had experienced more than 50 hours o£ 

directly relevant practice on the task complex as 

a participant (along with the other nine subjects) in earlier (non -drug) experiments. Thus, 

the workload imposed on the subjects by even 

the most demanding task combinations had, by 

the beginning o£ this study, been reduced to a 

minimum. However, it should be noted that the 

workloads. imposed by the heavier demand conditions (mental arithmetic plus group problem 

solving and visual discrimination plus problem 

solving) are quite high. Even the best subjects 

require something on the order o£ eight to ten 

repetitions o£ the basic 2-hour schedule before 

their performance begins to level off. Hence, it 

is argued that the various levels o£ workload 

used in the study provide reasonable approximations to the kinds o£ demands placed on the man 

involved in routine performances. It should be 

noted that the results might very well have been 

different with less well-trained subjects. 

It is concluded that the dosages o£ Donnatal 

or chlorpheniramine maleate used in our experiment do not have a deleterious effect upon highly 

trained subjects in the performance o£ the tasks 

that were assessed by this particular multiple 

task performance battery. The major qualification o£ this conclusion lies in the £act that only 

ten subjects were tested. Although this number 

o£ subjects is adequate £or the purposes o£ establishing average effects, it does not permit any 

detailed examination o£ individual differences in 

relation to the possible occurrence o£ idiosyncratic reactions o£ particular subjects.