PERSONALITY AND PHYSIOLOGICAL CORRELATES O

PERFORMANCE DECREMENT ON A MONOTONOUS 

TASK REQUIRING SUSTAINED ATTENTION 

FAA Civil Aeromedical Institute 

Richard I. Thackray, Ph.D. 

Karen N. Jones, B.S. 

Robert M. Touchstone, M.S. 

P.O. Box 25082 

Oklahoma City,Oklahoma 73125 

• 

~-. • 

December 1973 

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 
FM-AM-73-14 

4. Title and Subtitle 

PERSONALITY AND PHYSIOLOGICAL CORRELATES OF 

PERFORMANCE DECREMENT ON A MONOTONOUS TASK 

REQUIRING SUSTAINED ATTENTION 

7. Author( s) 

Richard I. Thackray, Ph.D., Karen N. Jones, B.S., 

and Robert M. Touchstone, M.S. 

9 . Performing Orgoni zation Name and Address 

FM Civil Aeromedical Institute 

P. 0. Box 25082 

Oklahoma City, Oklahoma 73125 

12. Sponsoring Agency Name and Addres• 

Office of Aviation Medicine 

Federal Aviation Administration 

800 Independence Avenue, S.W. 

Washington, D. C. 20591 

15. Supplementary Notes 

----------------~ 

5. Report Date 

December 1973 

6 . Performing Organization Code 

8. Performing Organization Report No. 

10. Work Un it No. 

II . Contract or Grant No. 

13. Type of Report ond Period Covered 

OAM Report 

14. Sponsoring Agency Code 

This research was performed under Tasks AM-A-72-PSY-32 and AM-A-73-PSY-32. 

16. Abstract 

The reductions in task load resulting from the increasing automation of air 

traffic control may actually increase the requirement for controllers to maintain 

high levels of sustained attention in order to detect infrequent system malfunctions. A previous study indicated that individuals scoring high on a 

distractibility scale found it difficult to maintain sustained attention on a 

monotonous, but perceptually demanding, task. The present study used the same 

serial reaction task to study other possible personality, as well as physiological, correlates of individual differences in performance decrement under 

low task-load conditions. Sixty subjects performed the task continuously for 

4"0 minutes. Extraverted subjects showed increasing lapses of attention, while 

introverted subjects failed to show any evidence of a decline in attention. 

Of the two extraversion components (impulsivity and sociability), impulsivity 

was the component responsible for the obtained decrement. Heart-rate variability 

showed a significant relationship with performance decrement while mean heart 

rate did not. 

17. Key Words 

Air Traffic Control 

Attention 

Extraversion 

Heart Rate 

Heart-Rate Variability 

19. Security Classif. (of this report) 

Unclassified 

Form DOT F 1100;7 18-691 

Impulsivity 

Monotony 

Vigilance 

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 13 $3.00 
ACKNOWLEDGMENTS 

The authors wish to gratefully acknowledge the assistance of Marilyn 

Dollar and Joe Bailey in scoring and analyzing the data of this study. 
PERSONALITY AND PHYSIOLOGICAL CORRELATES OF PERFORMANCE 

DECREMENT ON A MONOTONOUS TASK REQUIRING 

SUSTAINED ATTENTION 

I. Introduction. 

Projected trends in the automation of air 

traffic control suggest the possibility that the 

role of the future radar controller may be more 

of a system monitor than an active participant 

in traffic control.11 This reduction in task load 

is likely to increase rather than decrease demands 

upon the controller to maintain sustained attention in order to ensure his readiness to respond 

to an unexpected system malfunction or emergency situation. Although it is known that some 

individuals are better able than others to sustain 

attention under low task-load conditions, reasons 

for these differences are not fully understood. 

In a previous study by Thackray, Jones, and 

Touchstone,17 it was found that individuals who 

rated themselves as highly distractible in their 

daily lives were unable to sustain attention when 

required to perform a monotonous serial reaction 

task demanding continuous attention. In contrast, low distractibility subjects (Ss) were able 

to perform the task in a superior manner with 

no evidence of a decline in attention. The obtained decrement took the form of increasingly 

variable response times with frequent gaps or 

pauses which various investigators have hypothesized to be a reflection of declining task attention.2 10 The high and low distractibility groups 

did not show differing patterns of decrement in 

either mean response time or frequency of errors. 

The present study was an extension of the 

previous investigation and was designed to investigate other possible personality, as well as 

physiological, correlates of individual differences 

in performance decrement on this task. 

Although it is fairly well established that 

extraversion is related to performance decrement 

on both vigilance1 5 and serial reaction tasks,3 4 

a satisfactory explanation of why extraverts do 

more poorly than introverts on these tasks has 

not been developed. Using a factor analytic ap1 

proach, Eysenck and Eysenck8 hav~ dete~ined 

that extraversion is not a unitary d1menswn but 

rather consists of two main components, sociability and impulsivity. Since there is evidence that 

impulsivity is related to distractibility,12 the 

findings of a relationship between distractibility 

and performance decrement in the previous 

study by Thackray, Jones, and Touchstone17 

might suggest impulsivity rather than sociability 

to be the component of extraversion most directly 

related to vigilance decrement. The fiml.ings of 

a vigilance study by Krupski, Raskin, and 

Bakan14 also suggest this possibility. Impulsivity and sociability subscores of the Eysenck 

Personality Inventory9 were obtained and both 

found to be positively correlated with commission 

errors. While neither correlation was statistically 

significant, the higher value was obtained for 

impulsivity. 

On the basis of this previous research, it was 

hypothesized that extraversion would be positively related to performance decrement on the 

serial reaction task and that the obtained decrement would be primarily manifested in increased 

response variability. It was hypothesized further 

that, of the two extraversion components (impulsivity and sociability), impulsivity would 

show the greater relationship with the obtained 

decrement. 

A second aspect of the present study was to 

evaluate the use of heart-rate variability as a 

monitor of performance decrement. Evidence 

from a variety of studies suggests that this measure may be a sensitive physiological index of 

attention. Relative to resting conditions, heartrate variability has been shown to decrease markedly when attention is initially directed to task 

stimuli12 16 18 or when changes in the direction of 

increased task load occurY To the extent that 

attention declines during performance on a monotonous task, this decline should be reflected in 

increased heart-rate variability 
ship between heart-rate variability and performance decrement, it was felt that the measurement 

intervals were too few to adequately assess 

whether or not a relationship existed. in the 

present study, heart-rate data were continuously 

recorded and computer processed to provide a 

more adequate determination of possible relationships. It was hypothesized that heart-rate variability would show a progressive increase during 

the task session and that this increase would be 

positively correlated with performance decrement 

(increased response variability) on the serial 

reaction task. Since Thackray, Jones, and 

Touchstone17 failed to obtain any evidence of a 

change in mean heart rate during performance 

on this task, no relationship between mean heart 

rate and performance decrement was expected. 

II. Method. 

A. Subjects. Sixty paid college men served 

as Ss. None had any prior experience with the 

task used. 

B. Apparatus. The same serial reaction task 

employed in the previous .study11 was used in 

this study. This type of task appears ideal for 

studying the decrement function since it provides 

repetitive and monotonous stimulation, demands 

continuous discrimination, involves only minor 

physical fatigue, yields essentially continuous 

measures of response time, provides immediate 

feedback to the S, and gives a measure of errors 

as well as correct responses. 

The S 's · panel contained four lever-actuated 

microswitches arranged in a row 1% inches apart 

with a three-fourths inch diameter visual display 

centrally located over the keys. The visual display presented the numbers 1-4 . corresponding 

to keys 1-4 as numbered from left to right. A 

tape reader was used to present the numerical 

stimuli to the S. Stimuli consisted of a quasirandom series of numbers with the restrictions 

that no number occur twice in succession and 

that each number occur an equal number of times 

in the series. ThP. series was 300 stimuli in length 

and repeated itself automatically. 

Each time a given number appeared, the S 

attempted to press the corresponding key. If a 

correct response was made, the tape reader advanced, a new number was presented, and the 

2 

the correct key was pressed. Elapsed time between responses was measured by means of a 

Welford Mark V SETAR (Welford Bioelectronics Enterprises) and the data punched on paper 

tape. Response times were identified as to 

whether they corresponded to correct or incorr~ct 

responses. 

Heart rate was obtained from chest electrodes 

with the leads connected to a Beckman Type R 

Dynograph. Pulses from a cardiotachometer 

coupler were used as inputs to the SETAR for 

recording successive heart beats. 

C. Proced1.tre. Upon arriving for the experiment, the S was administered Form A of the 

Eysenck Personality Inventory (EPI). To minimize association between the inventory and the 

experiment, the S was not told that the personality scale was relevant to the present experiment, 

and one experimenter (E) administered the inventory while a different E conducted the rest of 

the experiment. 

Following completion of the inventory, the S 

was taken to the experimental room, instrumented 

for physiological recording, and the task instructions presented. Besides explaining the basic procedure, the instructions emphasized that the task 

should be performed as rapidly as possible but 

not at the expense of accuracy. 

After the task instructions, the S was given a 

one-minute practice trial and then told that he 

was to work continuously for approximately 50 

minutes. To prevent the S's knowing that the 

task was almost over, the experiment was stopped 

after 40 rather than 50 minutes. At this time, 

the E went into the experimental room, removed 

the electrodes, and asked the S to complete a postexper-imental questionnaire. 

D. llfeasurement of the Performance and Physiological Data. The performance data were computer processed and the following obtained for 

each S for each successive four-minute period of 

the session : 

(a) Mean response time 

(b) Standard deviation of the response times 

(response variability) 

(c) Number of incorrect responses 

For heart rate, a computer program was developed to yield two measures for each successive 

four-minute period during the performance ses-
Product-Moment Correlations Between Extraversion, 

Neuroticism, Impulsivity, and Sociability. 

1 

Extraversion 

2 

Neuroticism 

1 -.33** 

2 

3 

** .E. <:' • 0 1 

s1on. These measures were the mean rate and the 

standard deviation. Because of occasional muscle 

potential artifacts and premature contractions, 

the computer program was designed to reject any 

apparent heart beat interval which, when converted to a beat-per-minute (bpm) basis, exceeded 

160 bpm or fell below 30 bpm. In addition, any 

two successive heart beats which increased by 

more than 25 bpm or decreased by more than 46 

bpm were also rejected. These limits were empirically determined from preliminary handscored analyses and were felt to represent values 

for this set of experimental conditions which 

would maximize rejection of artifacts and minimize rejection of "valid" heart-rate data. 

III. Results. 

A. Personality Variables. Mean scores on the 

EPI were 12.3, 9.4, 4.0, and 5.4 for the extraversion, neuroticism, impulsivity, and sociability 

scales respectively. Table 1 shows the intercorrelations of these measurements. As expected, 

extraversion showed a significant, positive correlation with both impulsivity and sociability. 

The significant negative correlation between extraversion and neuroticism, however, was not 

expected. 

Although negative correlations between extraversion and neuroticism are frequently found, 

these are generally non-significant.9 Because a 

significant relationship was obtained between 

these two variables in the sample employed, neuroticism was separately examined even though it 

was not originally intended to do so. (Neuro3 

3 

Impulsivity 

.52** 

.00 

4 

Sociability 

.75** 

-.40** 

.03 

ticism has been frequently examined in vigilance-type studies and has typically shown no 

relationship to performance decrement.6 ) For 

each of the four scales, the 15 Ss with the highest 

and lowest scores were identified. The high and 

low cutoff scores for each distribution were as 

follows: extraversion (15 and 10), neuroticism 

( 12 and 6), impulsivity ( 5 and 3), and sociability 

(7 and 4). 

Since the neuroticism, extraversion, impulsivity, 

and sociability subgroups were each drawn from 

the same sample of 60 Ss, the total w:oup data 

for each performance measure were initially 

plotted in order to provide reference data for the 

comparison of differential response patterns of 

the Yarious subgroups. The data for mean response time, response variability, and frequency 

of errors for the 60 Ss are shown in Figure 1. 

Analyses of variance conducted on each set of 

data yielded significant F-value for the effect 

of four-minute perioQ.s for mean response time 

(F=4.16; p<.01), response variability (F= 

21.19; p<.01), and frequency of errors (F=12.79; 

p<.01 ). The only variable which did not reveal 

a progressive increase with time was mean response time. The abrupt increase in response 

time from period 1 to period 2 was also noted in 

the previous study17 and is apparently a characteristic of this task. Scheffe7 tests revealed that, 

while the difference between periods 1 and 10 

was significant ( F = 29.86; p < .005), the difference 

between periods 2 and 10 was not (F=4.96; 

p>.05). 
(/) 

0 

z 

0 

0 

w 

(/) 

(/) 

0 

z 

0 

0 

w 

(/) 

.80 

. 78 

.76 

.30 

.26 

.22 

. I 8 

.I 4 

I 0.4 

CJ) 

0:: 

0 8.8 

ct 

0:: 

w 7.2 

LL 

0 5.6 

0 

z 4.0 

,. 

MEAN RESPONSE TIME 

RESPONSE VARIABILITY (50) 

ERRORS 

2 3 4 5 6 7 8 9 10 

FOUR- MINUTE PERIODS 

FIGURE 1. Mean response time, response variability (standard deviation), and frequency of errors for each fourminute period of the task session. Data are for the total group of 60 Ss. 

Tables 2, 3, 4, and 5 present the results of 

analyses of variance conducted on the performance data of each subgroup. Since the betweenperiods effects were significant in the analyses 

of variance conducted on the data for all 60 Ss, 

it is not surprising that the differences between 

periods were significant for all variables in each 

subgroup with the exception of mean response 

time for extraversion. This F-value approached, 

but did not reach, significance at the 5 per cent 

level (p<.lO). None of the group differences 

was significant, but significant interactions were 

obtained between groups and periods for mean 

4 

response time on the extra version factor and for 

response variability on both the extraversion and 

impulsivity factors. Figure 2, which shows mean 

response time for the high and low extra version 

groups, displays generally increasing response 

times for the high group, but a mixed pattern 

for the low group. Tests of simple effects revealed the differences between periods to be significant for both the high (F=2.82; p<.Ol) and 

low (F=2.00; p<.05) groups. Figure 3 shows 

the response variability patterns for the high 

and low extraversion and impulsivity groups. 

There is a continuous rise in variability among 
Table 2 

Analyses of Variance of Mean Response Time, Response Variability, 

and Errors for Extreme Groups on Neuroticism. 

Mn Response Response 

Source db Time Variabiliti Errors 

MS F M> r MS F 

Between Ss 29 

A (Groups) 1 0.2483 2.05 0.0819 1.23 4.8891 0.54 

~s Within Groups 28 0.1211 0.0666 9.0855 

Within Ss 270 

B (Periods) 9 0.0036 2.48* 0.0345 12.74*** 4.9179 7.27*** 

A X B 9 0.0010 0.70 0.0031 1.13 0.5680 0.83 

~s Within Groups 252 0.0015 0.0027 0.6766 

* E. = . 05 ** E. = .01 ***E.= .001 

5 
Table 3 

Analyses of Variance of Mean Response Time, 

Response Variability, and Errors for Extreme Groups on Extraversion. 

Mn Response Response 

Source df Time Variabilit~ Errors 

MS E MS F MS F 

Between Ss 29 

A (Groups) 1 0.0013 0.01 0.0091 0.07 30.2713 3.62 

[s Within Groups 28 0.1865 0.1219 8.3636 

Within Ss 270 

B (Periods) 9 0.0033 1.80 0.0312 9.68*** 6.0700 8.64*** 

A X B 9 0.0055 3.03** 0.0089 2. 77** 0.4281 0.61 

[s Within Groups 252 0.0018 0.0032 0.7026 

* E. = .OS ** E. = .01 *** E. = .001 

6 
Table 4 

Analyses of Variance of Mean Response Time, Response Variability, 

and Errors for Extreme Groups on Impulsivity. 

Mn Response Response 

Source df Time Variabilit::l Errors 

MS F MS F MS F 

Between Ss 29 

A (Groups) 1 0.0870 0.53 0.0081 0.04 0.7802 0.01 

~s Within Groups 28 0.1630 0.1899 11.9390 

Within Ss 270 

B (Periods) 9 0.0054 2.28* 0.0509 9.51*** 6.1654 8.78*** 

A X B 9 0.0045 1.91 0.0109 2.03* 0.4487 0.64 

~s Within Groups 252 0.0023 0.0054 0.7019 

* E. = .OS ** E. = .01 *** E. = .001 

7 
Table 5 

Analyses of Variance of Mean Response Time, Response Variabili~y, 

and Errors for Extreme Groups on Sociability. 

Mn Response Response 

Source db Time Variabilit~ Errors 

MS F MS F MS F 

Between Ss 29 

A (Groups) 1 0.0337 0.28 0.0008 0. 01 4.1298 0.41 

~s Within Groups 28 0.1185 0.1608 9.9754 

Within Ss 270 

B (Periods) 9 0.0066 3.22** 0.0601 9.43*** 4.7696 6.28**

A X B 9 0.0031 1.52 0.0055 0.86 0.6066 0.80 

~s Within Groups 252 0.0020 0.0064 0.7597 

* £ = .OS ** £ = .01 *** £ = .001 

8 
C/) 

0 

z 

0 

(.) 

w 

C/) 

.82 

.81 

.8 0 

. 79 

.78 

.77 

.76 

.7 5 

1 

I 

I 

0 

,, 

I \ 

I \ 

I \ 

I \ 

o, 

2 3 

' 'o ' ' 'o 

' 

4 5 6 

"o I 

\\ I 

\ I 

\I 

0 

I 

0 

I 

I 

I 

• • HIGH 

o--o LOW 

7 8 9 

0 

I 

10 

FOUR- MINUTE PERIODS FIGURE 2. Mean response times for the high and low extraversion groups across periods. 

the high extraversion and impulsivity Ss during 

the experimental sessions with a relatively stable 

level of response variability among the low Ss. 

Tests of simple effects of periods revealed the 

differences between periods to be significant for 

the high extraversion (F=11.03; p<.001) and 

high impulsivity (F=9.59; p<.001) groups. 

There were no differences between periods for 

either the low extraversion (F=1.42; p>.05) or 

low impulsivity (F=1.74; p>.05) groups. 

B. Heart-Rate Measures. As expected, heartrate variability for the entire sample of 60 Ss 

showe~ a progressive, significant increase (F= 

20.64; p<.001) during the session. Mean heart 

rate showed a slight, but significant, decrease 

( F = 2.54; p < .01). These data are shown in 

9 

Figure 4. Since the previous study by Thackray, 

Jones, and Touchstone17 failed to find any change 

in mean heart rate, further tests were conducted 

on mean heart rate. Scheffe tests revealed no 

difference between periods 1 and 8 (F=1.53; 

p>.05) or between periods 1 and 10 (F=8.57; 

p > .05). The only significant difference was obtained when the periods with the highest (period 

2) and lowest (period 10) heart rates were compared (F=16.84; p=.05. 

The correlations of heart-rate variability and 

mean heart rate with performance variability are 

shown in Figure 5) . 

None of the correlations between perfonnance 

variability and mean heart rate was significant 

for any of the periods. Heart-rate variability 

was not significantly correlated with performance 
(f) 

0 

z 

0 

.30 

.26 

.22 

.I 8 

.I 4 

(.) 

w .34 

(f) 

.30 

.26 

.22 

.18 

.I 4 

o/ 

1 

_0., ,o--o-- ~__...--..-.r 

2 3 4 5 

-o- -o- -o- -o6 

EXTRAVERSION 

• • HIGH 

o--o LOW 

IMPULSIVITY 

7 

• • HIGH 

o- -o LOW 

8 9 

FOUR- MINUTE PERIODS 

-o 

10 

FIGURE 3. Response variability for the high and low extraversion and impulsivity groups across periods. 

10 
w 

~ 

~ 

z 

:E 

a:: 

w 

Cl. 

5.6 

5.2 

4.8 

4.4 

~ 73.5 

<( 

w 73.0 

m 

72.5 

72.0 

1 

2 3 

HEART RATE VARIABILITY 

MEAN HEART RATE 

4 5 6 7 8 9 10 

FOUR MINUTE PERIODS 

FIGURE 4. Mean heart rate and heart-rate variability (standard deviation) for each of the four-minute periods. 

Data shown are for all 60 Ss. 

variability during the first three periods, but 

showed significant and generally increasing correlations during the remaining seven periods. 

IV. Discussion. 

Increases in response variability on a serial reaction task have been shown to be largely the 

result of increases in the frequency and duration 

of gaps or pauses in performance.17 The present 

study revealed that Ss scoring high in extraversion displayed a continuous increase in response 

variability during the performance session, while 

Ss scoring low in extraversion (introverts) maintained a relatively uniform rate of responding. 

Since extraverts are known to exhibit more frequent pauses or blocks during performance on 

serial reaction4 and simple tapping15 tasks than 

do introverts, the present results would appear 

to support these previous findings. 

11 

Of greater interest was the predicted finding 

that impulsivity rather than sociability was the 

extra version factor primarily responsible for the 

obtained decreemnt. Although both impulsivity 

and sociability were significantly correlated with 

extraversion, only the high and low impulsivity 

groups showed response variability patterns 

which were similar to those of the high and low 

extraverts. This cannot be attributed simply to 

a sampling bias in whic,h a greater proportion 

of impulsivity than sociability Ss were drawn 

from the extraversion groups. The proportions 

were approximately equal with 57 per cent of 

the high and low impulsivity Ss and 63 per cent 

of the high and low sociability Ss common to the 

two extraversion groups. 

Neither errors nor means response time showed 

any appreciable relationship with any of the personality variables. The only exception was the 
z 

w 

(.) .32 

lL 

lL .24 

w 

0 

(.) .16 

z 

0 .08 

..... 

<t 0 ~ 

~- .08 

a:: 

8 - .16 

2 3 4 

FOUR 

0 = HEART RATE VARIABILITY 

0 = MEAN HEART RATE 

5 6 7 8 

MINU T E PE RIO DS 

9 1

FIGURE 5. Product-moment correlations of mean heart rate and heart-rate variability with performance variab

ity across periods. Data are for all 60 Ss. 

interaction obtained between extraversion and 

periods for mean response time. Extra verts 

showed a continuous increase in response time 

during the session, while introverts showed a 

mixed pattern consisting of an initial increase 

followed by a progressive decrease and a final 

increase. The meaning of this latter pattern is 

uncertain, although it reflects the general pattern 

obtained for the total group of 60 Ss. The lack 

of relationship between frequency of errors and 

any of the personality variables agrees with the 

lack of relationship between this measure and 

susceptibility to distraction obtained in the previous studyY Since Corcoran4 also failed to 

find a relationship between extraversioll'-introversion and frequency of errors using a similar task, 

it would appear that an increase in error frequency during serial reaction performance is 

either a poor index of declining attention or it 

reflects attentional processes unrelated to those 

manifested by increas~d response variability. 

While the negative correlation between extraversion and neuroticism was not anticipated, this 

small, though significant, correlat:lon does not 

alter interpretation of the results obtained. First, 

no relationships were found between neuroticism 

12 

and any of the performance measures. An

second, although impulsivity showed no corre

tion with neuroticism, the decrement pattern o

tained for impulsivity was essentially the same 

that obtained for extraversion. Thus, the neg

tive correlation is interpreted to reflect a comm

factor not related to performance decrement 

this type of task. 

The possible employment of heart-rate var

bility as a useful monitor of declining task atte

tion is suggested by the finding of a genera

increasing correlation between heart-rate var

bility and performance variability during t

session. Mean heart rate, on the other han

showed no relationship to response variabili

Research currently being planned will exami

the utility of employing heart-rate variability 

a monitor of declining attention during perfor

ance of a more complex task involving a lar

number of visual inputs with infrequency chan

ing critical stimuli. 

V. Summary. 

The present study revealed that Ss scori

highest on an extraversion scale found it diffic

to maintain a uniform rate of responding on 

serial reaction task over a 40-minute period. T
variable response times which previous studies 

have suggested is a reflection of declining task 

attention. Individuals scoring low in extraversion (introverts) showed no evidence of this kind 

of performance decrement. The study further 

revealed that, of the two dimensions of extraversion (impulsivity and sociabiHty), impulsivity 

was the component more closely related to the 

obtained decrement. Taken together with the 

findings of a previous study by the same authors, 

variables including distractibility, extraversion, 

and impulsivity which describe individuals who 

find it difficult to maintain sustained attention 

under monotonous, low task-load conditions. 

The study also explored the use of mean heart 

rate and heart-rate variability as indices of declining attention. As predicted from previous 

studies, heart-rate variability showed significant 

relationships with performance variability during 

the session while mean heart rate did not. 

REFERENCES 

1. Bakan, P.: Extraversion-Introversion and Improvement in an Auditory , Vigilance Task, BRITISH 

JOURNAL OF PSYCHOLOGY, 50 :325-332, 1959. 

2. Broadbent, D. E.: Decision and Stress, London Academic Press, Inc., 1971. 

3. Claridge, G. S. : Personality and Arousal, London, 

Pergamon Press, 1967. 

4. Corcoran, D. W. J . : Personality and the Inverted-U 

Relation, BRITISH JOURNAL OF PSYCHOLOGY, 

56 :267-273, 1965. 

5. Davis, D. R., and G. R. J. Hockey: The Eft'ects of 

Noise and Doubling the Signal Frequency on Individual Dift'erences in Visual Vigilance Performance, 

BRITISH JOURNAL OF PSYCHOLOGY, 57 :381-

389, 1966. 

6. Davis, D. R., and G. S. Tune: Human Vi-gilance Performance, New York, American Elsevier Publishing 

Company, Inc., 1969. 

7. Edwards, A. L.: Experimental D esign in Psychological Research, New York Holt, 1960. 

8. Eysenck, S. B. G., and H. J. Eysenck: On the Dual 

Nature of Extraversion, BRITISH JOURNAL OF 

SOCIAL AND CLINICAL PSYCHOLOGY, 2 :46-55, 

1963. 

9. Eysenck, H. J., and S. B. G. Eysenck: Eysenclc Personality Inventory, San Diego, Education and Industrial Testing Service, 1968. 

10. Faulkner, T. W.: Variability of Performance in a 

Vigilance Task, JOURNAL OF APPLIED PSYCHOLOGY, 46:325-328, 1962. 

11. Hopkin, V. D. : Human Factors in ATC. Swedish 

Society of Aeronautics and Astronautics, International Symposium on Air Traffic Control, Stockholm, 

13 

Sweden, March 1969, Proceedings. Stockholm, Swedish Society of Aeronautics and Astronautics, 1970, 

329-339 and 341-344. 

12. Kagan, J., and B. L. Rosman: Cardiac and Respiratory Correlates of Attention and an Analytic Attitude, 

JOURNAL OF EXPERIMENTAL AND CHILD 

PSYCHOLOGY, 1 :50-63, 1964. 

13. Kalsbeek, J. W. H.: Measurment of Mental Work 

Load and of Acceptable Load : Possible Applications 

in Industry, INTERNATIONAL JOURNAL OF PRODUCTION, 7 :33-45, 1968. 

14. Krupski, A., D. C. Raskin, and P. Bakan : Physiological and Personality Correlates of Commission 

Errors in an Auditory Vigilance Task, PSYCHOPHYSIOLOGY, 8:304--311, 1971. 

15. Spielmann, J.: The Relation Between Personality and 

the Frequency and Duration of Involuntary' Rest 

Pauses During Massed Practice, London, Unpublished 

Ph.D. thesis, 1963. Cited by Eysehck, H. J:·: The 

Biological Basis of Personality, Springfield, Charles 

C. Thomas, 1967. 

16. Thackray, R. I. : Patterns of Physiological Activity 

Accompanying Performance on a Perceptual-Motor 

Task. FAA Office of Aviation Medicine Report No. 

AM-69-8, 1969. 

17. Thackray, R. 1., K. N. Jones, and R. M. Touchstone : 

Self-Estimates of Distractibility as Related to Performance Decrement on a Task Requiring Sustained 

Attention, ERGONOMICS, 1973 (in press). 

18: Welford, N. T.: Heart-Rate Variability During Continuous Performance. Paper presented at the meeting of the American Association for the Advancement 

of Science, Dallas, December 1968.