AM GS-17 

THE EFFECTS OF COGNITIVE APPRAISAL OF STRESS 

ON HEART RATE AND TASK PERFORMANCE 

Richard I. Thackray, Ph.D. 

David W. Pearson 

Approved by Released by 

~~ J. RoBERT DILLE, M.D. P. v . .SIEGEL, M.D. 

23823 

CHIEF' CIVIL AEROMEDICAL 

INSTITUTE 

FEDERAL AIR SURGEON 

September 1968 

Department of Transportation 

FEDERAL AVIATION ADMINISTRATION 

Office of Aviation Medicine 
THE EFFECTS OF COGNITIVE APPRAISAL OF STRESS ON HEART 

RATE AND TASK PERFORMANCE 

I. Introduction. 

In aviation occupations, performance impairment under stress conditions is particularly undesirable. However, it is known that individuals 

differ widely in stress susceptibility. 3 Some individuals exposed to a given stress situation will 

show performance impairment, some may improve in performance, and others show no apparent change.7 Previous attempts to identify, 

through the use of conventional anxiety scales, 

those individuals who may show performance impairment to a particular stress condition have 

generally not been too successfuU Within the 

past few years, increasing emphasis in stress research is being placed on the more direct approach of determining an individual's attitude 

toward a specific stress situation, under the assumption that attitudes should be significant 

determinants of behavioral and physiological response to the stressor.5 

In adopting the position that cognitive appraisal of threat is a factor of major importance 

in accounting for individual differences in stress 

susceptibility, Hodges and Spielberger2 recently 

hypothesized that in a given stress situation, such 

as threat of shock, subjects who had expressed a 

high fear of shock would differ from low fear of 

shock subjects in their over-all response to the 

stressor. Their general findings were that subjects classified as having high fear of shock on 

the basis of a questionnaire item administered 

several months prior to the experiment gave 

significantly greater heart rate increase to threat 

of shock than subjects classified as low fear of 

shock. Subjects were not aware prior to the 

aetual administration of threat that the experiment involved any shock or threat of shock. In 

addition the study found no difference in the 

heart rate response of high and low anxious subjects to threat of shock when subjects were separated on the basis of scores on the Taylor 

Manifest Anxiety Scale.11 

1 

The present study was designed to replicate 

the essential findings of Hodges and Spielberger 

and hopefully also to relate performance change 

under stress to individual differences in cognitive 

appraisal. It was predicted that (a) subjects expressing a high fear of shock would reveal 

greater heart rate acceleration to threat of shock 

than low fear of shock subjects and (b) under 

threat of shock, high fear of shock subjects would 

demonstrate greater performance impairment on 

a motor (pursuit rotor) task than low fear of 

shock subjects. A subsidiary aspect of the study 

explored the question of control vs. lack of control as a faetor influeneing the magnitude of 

stress response. 

II. Method. 

Subjects. The subjects were male undergraduates obtained from introductory psychology 

courses at Oklahoma University. They were selected from a larger group which had been administered a questionnaire relating to a variety 

of potentially stressful situations approximately 

one month prior to the experiment. Each item 

was answered in terms of a five-point scale 

ranging from "not stressful" to "extremely stressful." The specific item used for selection was "receiving an electric shock." Subjects responding 

above the midpoint were classified as high fear 

of shock (HFS) subjects and those responding 

below the midpoint as low fear of shock (LFS) 

subjects. No information was provided any of 

the subjects contacted other than that they had 

been randomly selected to participate in a psychological experiment involving motor learning. A 

total of 24 HFS and 24 LFS subjects were used 

in the experiment. 

Apparatus. The basic performance equipment 

consisted of a pursuit rotor (Lafayette Instrument Co.) and electric stop elock. The pursuit 

rotor was set to a rota tiona~ speed of 60 RPM and 

maintained at this speed throughout the experi-
ment. An Applegate Model 230 stimulator served 

as the dummy "shock apparatus." Heart rate 

(HR) was obtained by means of a Gulton finger 

pulse transducer and recorded on a Beckman 

TypeR Dynograph. The subject, all equipment, 

and the experimenter were located in the same 

room. The subject sat at a small table which 

held the pursuit rotor. A tape recorder was used 

to present all the instructions given to the subject. 

Procedure. Upon arriving for the experiment, 

each subject was assigned according to a quasi 

random procedure to one of three conditions: 

Control (C); shock contingent (SC); or shock 

noncontingent (SNC). A total of eight subjects 

was assigned to each of these conditions in each 

(HFS arrd LFS) group. The subject was then 

ta:ken to the experimental room and introduced 

to the experimenter who had no knowledge as to 

whether he was a HF'S or LFS subject. Following the administration of several questionnaires, 

including the Taylor11 Manifest Anxiety Scale 

(MAS), the subject was seated at a table holding 

the pursuit rotor and the initial instructions 

played. These instructions, which were the same 

for all subjects, explained how the task was to be 

performed during the initial training phase. The 

subject was told that the purpose of the experiment was to study the effects of generalized 

muscle tension on learning and that this was the 

reason for the finger sensor. After the instructions were finished, the pulse transducer was attached to the index finger of the subject's nonpreferred hand and the Dynograph adjusted. 

Fifteen training trials were then administered. 

Each trial was of 20 seconds duration with 20 

second rest periods between trials. Total time 

that the stylus was in contact with the metal disk 

on the pursuit rotor was recorded by the experimenter at the end of each trial. HR was recorded continuously during this period and 

during the remainder of the experiment. 

Following the completion of training, subjects 

in the two shock threat groups were played instructions which in essence informed them that 

during the next phase of the experiment they 

would be required to perform under pressure. 

The subjects assigned to the SNC condition were 

told they would receive an uncomfortable, but 

harmless electric shock at random intervals 

during some trial. It was emphasized that the 

shock was randomly programmed by the shock 

apparatus and that neither the subject nor the 

2 

experimenter had any control over when it would 

occur. The subjects in the SC condition were 

also informed that they would receive an uncomfortable, but harmless shock. However, their 

instructions stated that this would only occur 

if their performance dropped below the average 

score they attained during training. They were 

told that the shock apparatus would be set to 

their average score, and that it would automatically deliver a shock whenever their performance fell below this value. Following completion of these instructions to a subject assigned 

to either of these two conditions, the experimenter brought out a rather impressive looking 

shock apparatus which had been previously 

hidden in a cabinet and placed it on a table next 

to the subject. Two EKG plate electrodes were 

attached to the subject's right leg and connected 

through a dummy cable to the shock apparatus. 

The apparatus was then plugged into a wall out1st and the experimenter manipulated several 

dials, presumably setting information into the 

machine. No questions were answered by the 

experimenter during this or any other phase of 

the experiment. The subjects assigned to the C 

condition were given reading material ( a financial newsletter) during the period occupied by 

the shock threat instructions. AU subjects were 

then given fifteen additional trials on the pursuit 

rotor. 

During the post experimental inquiry, subjects 

in the SC condition were congratulated on having 

avoided the shock, while subjects in the SNC 

condition were questioned as to their reaction to 

the shock. Since they generally reported feeling 

little or nothing, the experimenter acted rather 

surprised and said that they must have been 

lucky. It was then explained that the shock apparatus had also been randomly programmed for 

various intensities of shock and they were fortunate in having received some very mild ones. 

Since no shocks were actually used in the experiment, this information was felt necessary to provide the subjects in the SNC condition with some 

explanation as to why no shocks occurred. In 

addition, it also served to reduce the possibility 

of feedback to other subjects that the experiment 

involved shock threat, but that no shocks were 

really used. 

111 easures. Heart rate was measured only during 

the 20-second inter-trial intervals and then con-
14 . 

c 12 ~ LFS ·-E 

' 10 D (/) 

~ HFS a 

Q) 8 

.0 

c 6 

Q) 

Ol 4 

c 

a 2 .r:. 

u 

0:: 0 

I 

-2 

c SNC sc 

FIGURE 1. Mean heart rate change from the training period to the test period for high fear of shock ( HFS) and low 

J'ear of shock ( LFS) groups administered control ( 0), shock noncontingent ( SNO), and shock contingent (SO) 

instructions. 

+--

Q) 4.0 

01 

'-

0 3.6 1-

~LFS 

c 3.2 0 

(/) 

u 2.8 Q) 

DHFS 

(/) 

Q) 2.4 

E 

1- 2.0 

c 

Q) 1.6 (/) 

0 

Q) I. 2 '-

u 

c 

c SNC sc 

FIGURE 2. Mean performance increase from the training period to the test period for the high fear of shock (HFS) 

and low fear of shock (LFS) gt•oups administered control (0), shock noncontingent ( SNO) and shock contingent 

(SO) instructions. 

verted to beats per minute. This was necessary 

because movement artifacts which occurred in the 

records of some subjects during task performance 

3 

made it virtually impossible to accurately determine HR. Performance scores consisted of the 

total time on target in each 20-second period. 
III. Results. 

Mean HR during the total training period was 

obtained for each subject in the three LFS and 

HFS groups. Likewise, th0 mean time on target 

during the last five training trials was obtained 

for each subject in each group. Examination o£ 

the data revealed that the major portion of learning occurred during the first ten trials. Thus, 

the mean of the last five trials appeared to provide the most appropriate measure of performance level during the training period. Two-way 

analyses of variance conducted on both sets of 

data revealed no main effects or interactions 

significant at the five per cent point. 

In evaluating the effects of the experimental 

conditions, it was decided to confine the primary 

analysis to the change in HR or performance 

occurring during the first test trial only.* Since 

no actual shocks were employed in the study it 

was expected that the effects of threat would be 

maximal during this period and would tend to 

decline without subsequent reinforcement. Consequently, the algebraic difference in HR between 

the 20-second period following the first test trial 

and the mean of the preceding training trials was 

obtained for each subject. For performance data 

the algebraic difference between each subject's 

score on his first test trial and the mean of his 

preceding five training trials was obtained. 

The mean change scores for the three HFS and 

LFS groups are shown in Figures 1 and 2, with 

Figure 1 displaying the HR data and Figure 2 

the performance data. 

The effect of the experimental conditions on HR 

of the HFS and LFS groups was evaluated by 

a two-way analysis of variance. The summary 

analysis presented in Table 1 indicates that only 

the experimental conditions yield a significant F 

value. 

TABLE 1. Summary Analysis of Variance of the Effects 

of Threat of Shock on HR of High and Low Fear 

of Shock Subjects. 

Source df MS F 

Experimental Conditions 2 349 6.84* 

Fear of Shock 1 99 1.94 

Experimental Conditions X 

Fear of Shock 2 133 2.60 

Error 42 51 

*p<.05 

*The remaining 14 trials were included in the design for 

another purpose and will not be reported here. 

4 

Orthogonal comparisons12 revealed the HR increase of the SC-HFS group to be significantly 

greater than its control group (F=12.5, p<.05), 

while no significance was found for the SC-LFS 

vs. C-LFS comparison. Although both HFS 

and LFS groups showed an increase in HR with 

respect to their control groups under the SNC 

condition, only the LFS orthogonal comparison 

was significant (F=6.35, p<.05). 

A similar analysis of variance was conducted 

on the performance data of Figure 2. The 

summary analysis presented in Table 2 reveals 

that both main effects are significant. 

TABLE 2. Summary Analysis of Variance of the Effects 

of Shock on Performance Scores of High and Low 

Fear of Shock Subjects. 

Source df MS F 

Experimental Conditions 2 4.96 3.39* 

Fear of Shock 1 8.82 6.04* 

Experimental Conditions X 

Fear of Shock 2 1.30 .89 

Error 42 1.46 

*p<.05 

Orthogonal comparisons support the HR data 

by revealing a significant difference (F=4.7'7, 

p<.05) between SC-HFS vs. C-HFS, but no 

significance between the SC-LFS vs. C-LFS 

comparison. However, while both of the SNC 

groups showed an apparent impairment of performance with reference to their respective control groups, the comparisons were not significant. 

Since all subjects were administered the MAS, 

the distribution of scores on this scale was split 

at the median and the resulting classification 

compared with the high and low fear of shock 

classification. A tetrachoric correlation coefficient of .08 with a corresponding chi square value 

of .1'5 (p>.05) indicated no relationship between 

fear of shock and manifest anxiety. 

IV. Discussion. 

The results offer at least partial support for 

the original findings of Hodges and Spielberger2 

of a relationship between expressed fear of shock 

and response to a shock threat situation. However, the most interesting and somewhat unexpected finding of the present study was the differing effects of the shock threat contingencies 

on both HR and performance for the high and 

low fear of shock groups. Thus, in comparing 

the shock contingent and shock noncontingent 

conditions, it was the HFS group under the 
shock contingent condition which showed the 

most pronounced change in HR and performance 

relative to its control. The LFS group under the 

same threat condition did not differ from its 

control in either HR or performance. While 

the results for the shock contingent threat condition clearly support the original hypothesis of 

greater performance impairment and HR change 

under shock threat for HFS subjects, the results 

for the noncontingent threat condition are some 

what more ambiguous. Although both HFS and 

LF'S subjects revealed similar changes in HR and 

performance under this latter condition, there 

was no evidence to suggest a greater stress response among the HFS subjects. The similarity 

of the trends for HFS and LFS subjects in both 

HR and performance data suggests that the non· 

contingent threat condition probably exerted a 

weak, but equal stress effect on all subjects regardless of expressed fear of shock. If this 

interpretation is correct, the significantly greater 

HR increase for the LFS group relative to its 

control would be simply a reflection of a general, 

weak stress effect acting across all subjects. 

The question of why the predicted effects of 

shock threat occurred only under the shock contingent condition is somewhat puzzling. To the 

extent that this condition was perceived by HFS 

subjects as allowing a means of controlling the 

occurrence of shock and thereby offering a way 

of coping with the stress, it would seem that introducing a threat of shock which is contingent 

on performance would result in less stress for 

HFS subjects than the SNC condition in which 

no control over the stressor was possible. There 

is evidence from a number of related studies 

which would suggest that the opportunity for a 

coping response should reduce stress behavior.6 •

9 

Such studies, however, have typically been concerned with the effects of ego-defense mechanisms 

such as denial, reaction formation, or intellectualization in reducing reaction to stress. There is 

apparently very little experimental evidence to 

5 

sugg-est that allowing a subject the means of 

possibly avoiding the occurrence of a stressor 

through some imtrUJnental act would necessarily 

also serve to reduce stress. Indeed, it is entirely 

possible that such control could actually enhance 

the total stress effect. Thus, one of the few 

studies with results in apparent accord with the 

findings of the present study is the well-known 

"executive monkey" study in which animals who 

could avoid shock through an operant response 

showed extensive gastrointestinal lesions, while 

their controls who received the same shocks, but 

not related to any instrumental response, showed 

no damage.8 

The results suggest that under certain conditions the introduction of an apparently appropriate coping response may result in greater stress 

than a situation in which no control is possible. 

What the conditions are which determine this is 

a question for future research. With regard to 

the SC condition, possibly some degree of control 

over the occurrence of a stressor serves to reduce 

stress when threat is not too great. However, 

when the level of threat becomes excessive, as it 

may have with the HFS subjects in the present 

study, control may act to actually increase the 

stress response. 

In neither the present study nor the previous 

one by Hodges and Spielberger2 was a relationship found between fear of shock classification 

and scores on the MAS. A lack of relationship 

between the MAS and response to threat of shock 

has recently also been shown for skin resistance 

activity as well. 4 These results, taken together, 

suggest that a measure of trait anxiety10 such as 

the MAS is considerably less effective in predicting response to a shock stress situation than a 

measure based upon cognitive appraisal of shock 

threat. Further research is needed to determine 

whether measures of cognitive appraisal of 

threat prove to be as effective in predicting response to stress situations other than shock. 
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In R. GLASER (Ed.), Training 1·esearch and education. 

Pittsburgh: University of Pittsburgh Press, 1962. 

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shock on heart rate for subjects who differ in manifest anxiety and fear of shock. Psychophysiology, 

2 :287-294, 1966. 

3. HoRVATH, F. E. Psychological stress: 

definitions and experimental research. 

tems Yearbook, 4:203-231, 1959. 

A review of 

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and two indices of autonomic response to stress. 

Journal of Personality and Social Psychology, 2:324-

333, 1965. 

5. LAZARUS, R. S. Psychological stress and the coping 

process. New York: McGraw-Hill, 1966. 

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by experimentally altering cognitive appraisal. 

Journal of Abnonnal and Social Psychology, 69:195-

205, 1964. 

6 

7. LAZARUS, R. S., DEESE, J., & OSLER, S. F. The effects of psychological stress upon performance. 

Psychological Bulletin, 49 :293-317, 1952. 

8. PORTER, R. W., BRADY, J. V., CONRAD, D., MASON, J.W., 

GALAMBOS, R., & RiocH, D. M. Some experimental 

observations on gastrointestinal lesions in behaviorally conditioned monkeys. Psychosomatic Medicine, 20 :379-394, 1958. 

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DAVISON, L. Experimental reduction of stress based 

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In C. D. SPIELBERGER (Ed.), Anxiety and behavior. 

New York: Academic Press, 1966. 

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