F AA-AM-72-25 

SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO 

PERFORMANCE DECREMENT ON A TASK REQUIRING 

SUSTAINED ATTENTION 

Richard I. Thackray, Ph.D. 

Karen N. Jones, B.S. 

R. Mark Touchstone, M.S. 

FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma 73125 

July 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 

::\ledicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO PERFORMANCE 

DECREMENT ON A TASK REQUIRING SUSTAINED ATTENTION by Richard I. Thackray, Karen N. Jones, and R. Mark Touchstone, July 1972, 

8 pp. Report No. FAA-AM-72-25. 

Increasing automation of air traffic control tasks may have 

the undesirable side effect of increased monotony as a result 

of the anticipated reduction in task demands. While the 

actual extent of increase in monotony resulting from such 

automation is not as yet known, it is known that performance 

during low task-load conditions is accompanied by declining 

attention. Since individuals who are unable to sustain attention under low task-load conditions would appear to be more 

likely to commit errors and less able to handle a sudden 

emergency situation, it would seem desirable to examine the 

characteristics of individuals unable to sustain attention under 

these conditions. In the present study, 50 subjects performed 

a monotonous, but perceptually demanding task, for approximately 30 minutes without rest. It was .found that highdistractibility subjects (as determined from a questionnaire 

administered prior to the experiment) showed increasing 

lapses of attention during performance, while low-distractibility subjects failed to show any evidence of a decline in atten- tion. Significant changes were obtained for respiration, 

respiration-period variability, heart-rate variability, and skin 

conductance during the task period, but the magnitude of 

these changes did not differ among the two distractibility 

groups. 

I. Thackray, 

R.I. 

II. Jones, K. N. 

III. Touchstone, 

R. 1\I. 

Descriptors 

Attention 

Distractibility 

Monotony 

Vigilance 

Federal Aviation Admini

:Medicine, Civil Aeromed

City, Oklahoma. SELF

TRACTIBILITY AS RELA

DECREMENT ON A T

TAINED ATTENTION 

Karen N. Jones, and R. l\

8 pp. Report No. FAA-AM

Increasing automation of 

the undesirable side effec

of the anticipated reduc

actual extent of increase 

automation is not as yet k

during low task-load con

attention. Since individu

tion under low task-load 

likely to commit errors 

emergency situation, it w

characteristics of individu

these conditions. In the p

a monotonous, but percep

mately 30 minutes witho

distractibility subjects (a

administered prior to t

lapses of attention during 

ity subjects failed to show 

tion. Significant change

respiration-period variabil

conductance during the 

these changes did not d

groups. 
Federal Aviation Administr ation, 

Office of Aviation 

Medicine, Civil Aeromedical I nstitute, Oklahoma 

City, 

Oklahoma. SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO PERFOR

MANCE 

DECREMENT ON A TASK REQUIRI

NG SUSTAINED ATTENTION by Richard I. Thackray, 

Karen N. Jones, and R. Mark Touchstone, July 1972, 

8 pp. Report No. FAA-AM-72-25. 

Increasing automation of air traffic control tasks may have the undesirable side effect of increased monotony as a result of the anticipated reduction in task demands. While the 

actual extent of increase in monotony resulting from such automation is not as yet known, it is known that performance during low task-load conditions is accompanied by declining 

attention. Since individuals who are unable to sustain attention under low task-load conditions would appear to be more 

likely to commit errors and less able to handle a sudden 

emergency situation, it would seem desirable to examine the cha racteristics of individuals unable to sustain attention under 

these conditions. In the present study, 50 subjects performed 

a monotonous, but perceptually demanding task, for approximately 30 

minutes without rest. It was .found that highI. Thackray, R.I. II. J ones, K. 

N. 

III. Touchstone, 

R. M. 

Descriptors 

Attention 

Distractibility 

Monotony 

Vigilance 

Federal Aviation Administ

Medicine, Civil Aeromedi

City, Oklahoma. SELF-

TRACTIBILITY 

AS REL

AT

DECREME

NT 

ON A TA

TAI

NED ATTE

NTION b

Karen N. Jones, and R. Ma

8 pp. Report No. FA

A-AM

Increasing automation of 

the undesirable side effect 

of the anticipated reducti

actual extent of increase 

automation is not as yet kn

during low task-load condi

attention. Since individual

tion under low task-load co

likely to commit errors a

emergency situation, it wou

characteristics of individual

these conditions. In the pr

a monotonous, but perceptu

mately 30 minutes withou

:·---·-------------------------------------------------------------------------------------------------------------:. 

_____ ___ ___ _______ ___________ ___ 

-------

distr actibility subjects (as determined from a questionnaire 

administered prior to the experiment) showed increasing 

lapses of attention during performance, while low-distractibility subjects failed to show any evidence of a decline in atten- tion. Significant changes obtained for respiration, 

respiration-period variability, heart-rate variability, and skin conductance during the task period, but the magnitude of 

these changes did not differ among the two distractibility 

groups. 

distractibility subjects (as 

administered prior to the 

lapses of attention during ity subjects failed to show 

tion. Significant changes 

respiration-period variabilit

conductance during the ta

these changes did not dif

groups. 
FAA-AM-72-25 

4. Title and Subtitle 

SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO 

PERFORMANCE DECREMENT ON A TASK REQUIRING SUSTAINED 

ATTENTION 

7. Author( s) 

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

and R. Mark Touchstone, M.S. 

9 . Performing Orgoni zotion Nome and Address 

FAA Civil Aeromedical Institute 

P. 0. Box 25082 

Oklahoma City, Oklahoma 73125 

5. Report Date 

July 1972 

6 . Performing Organization Code 

8. Performing Organization Report No. 

10 . Work Unit No. 

11 . Contract or Grant No. 

~-------------.,...,....---------- -----------1 13. Type of Report and Period Covered 

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 

OAM Report 

14 . Sponsoring Age ncy Code 

This research was performed under Task AM-A-72-PSY-32. 

16. Abstract 

Increasing automation of air traffic control tasks may have the undesirable 

side effect of increased monotony as a result of the anticipated reduction in 

task demands. While the actual extent of increase in monotony resulting from 

such automation is not as yet known, it is known that performance during low 

task-load conditions is accompanied by declining attention. Since individuals 

who are unable to sustain attention under low task-load conditions would 

appear to be more likely to commit errors and less able to handle a sudden 

emergency situation, it would seem desirable to examine the characteristics 

of individuals unable to sustain attention under these conditions. In the 

present study, 50 subjects performed a monotonous, but perceptually demanding 

task, for approximately 30 minutes without rest. It was found that highdistractibility subjects (as determined from a questionnaire administered 

prior to the experiment) showed increasing lapses of attention during performance, while low-distractibility subjects failed to show any evidence of 

a decline in attention. Significant changes were obtained for respiration, 

respiration-period variability, heart-rate variability, and skin conductance 

during the task period, but the magnitude of these changes did not differ 

among the two distractibility groups. 

17. K~y Words 

Attention 

Distractibility 

Monotony 

Vigilance 

19. Security Classif. (of this report) 

Unclassified 

Form DOT F 1700.7 <e-691 

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. Na. of Pages 22. Price 

Unclassified 8 $3.00 
SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO PERFORMANC

DECREMENT ON A TASK REQUIRING SUSTAINED ATTENTION 

I. Introduction. 

It has been suggested that increasina automation of air traffic control tasks may "'have the 

undesirable side effect of increased monotony and 

boredom as a result of the anticipated reduction 

in task demands.13 "While the actual extent of 

increase in monotony resulting from such automation is not as yet known, it is known that 

performance during low task-load conditions 

(especially if this is prolonged) is accompanied 

by declining6 12 or increasingly variable attention.9 11 Since individuals who are unable to 

sustain attention under low task-load conditions 

would appear to be more likely to commit errors 

and less able to handle a sudden emeraency situation, it would seem desirable to ex:mine the 

characteristics of individuals unable to sustain 

attention under these conditions. 

Laboratory studies of prolonged performance 

on monotonous tasks commonly reveal a proares- • b 

s1ve decrement over time. Although this decline 

has been studied most frequently in viailance 

tasks, it is also known to occur in trackina0 

serial . . "'' 

reactwn, and a variety of auditory and visual discrimination tasksY The decline is generally exponential in form and usually becomes apparent 

within a half-hour of work.8 17 Since all of these 

tasks demand continuous attention to a relatively 

monotonous or repetitive situation with minimal 

muscular requirements, the decrement does not 

seem to be a simple consequence of response fatigue. Rather, it appears to involve a decline in 

some central attentional process which in turn 

is known to promote or induce drowsiness, microsleep episodes, lapses of attention, and certain 

trance-like (highway-hypnotic) conditions.19 

Although it is known that some individuals are 

better able than others to sustain performance 

under monotonous conditions, the reasons for 

these individual differences are not completely 

understood. Attempts to relate these differences 

to such variables as sex, intelligence, and age 

1 

have generally been unsuccessful in demonstr

ing significant relationships.8 17 Somewh

greater success has· been obtained with measur

of temperament, e.g., extroversion-introversio

A frequent finding is that extroverts tend 

show a progressive decrement with time on ta

while introverts appear better able to susta

performance at a relatively constant leveU 7 

should be noted, however, that a number of neg

tive findings have been reported8 10 and the re

tionship is further clouded by the fact that, w

respect to errors of commission in vigilance p

formance, introverts sometimes show a grea

error frequency than extroverts.8 

Relatively few studies have examined relatio

ships between cognitive variables and perfor

ance decrement on monotonous tasks. Antrob

Coleman, and 'Singer1 hypothesized that in

viduals who had a high propensity to daydrea

would become increasingly involved in their o

thought processes during monotonous task p

formance and exhibit greater decrement th

individuals with less tendency to daydrea

Subjects (Ss) were selected who scored at t

extremes on a "daydreaming" questionnaire a

compared with respect to their ability to det

signals on an auditory vigilance task. Wh

high and low daydreaming Ss did not differ 

total number of signals detected, when these w

averaged across trials, a comparison of the tren

exhibited by the two groups revealed a proar

sive and significant decrease in the numbe~ 

signals detected from the beginning to the e

of the session for high daydreaming Ss, but 

change for the lows. The results of the Antrob

Coleman, and Singer study suggest that in

viduals who have a predisposition to daydrea

ing in their daily life tend to shift their attenti

inward during monotonous performance, there

reducing their attentiveness to the task stimuli

The present study was concerned with t

question of whether Ss who rated themselv
gy py 

lives would also find it difficult to maintain concentration under a low task-load condition with 

minimal sensory stimulation. It was predicted 

that such Ss would find it increasingly difficult 

to sustain attention under these conditions and 

that this would be reflected in a progressive increase in both incorrect responses and performance variability. 

A second aspect of this study was to examine 

the relationships between change in certain 

psychophysiological variables during the session 

and relative performance decrement of Ss differing in self-related distractibility. The measures 

employed were heart rate, heart-rate variability, 

respiration period, respiration-period variability, 

and palmar skin conductance. Although heart 

rate and skin conductance ha.-e been frequently 

studied and generally found to decline during 

vigilance performance,8 the direction and magnitude of change in these other measures during 

monotonous performance is less clearly understood. Evidence from a variety of studies, however, suggests that they may be quite sensitive 

to decline in attention. Increases in attentional 

requirements are known to be accompanied by 

decreased heart-rate variability, respiration period, and respiration-period yariability.14 16 21 24 

Thus, declining attention during task performance should be associated with increases in these 

latter three variables, but decreases in skin conductance and heart rate. It was predicted that 

high-distractibility Ss would show this physiological response pattern to a greater extent than 

low-distractibility Ss. 

II. Method. 

A. Subjects. Fifty paid college men served as 

Ss. None had any prior experience with the task 

used. 

B. Apparatus. The task employed was a selfpaced serial reaction task similar to that used by 

Bertelson and Jo:ffe3 and Shor and Thackray.79 

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, and 

gives a measure of errors as well as correct responses.19 

2 

p

microswitches arranged in a row 1% inches apart 

with a % 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 quasi-random 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. 

The 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 

cycle continued. If an incorrect response was 

made, the visual stimulus did not change until 

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 incorrect (error) responses. 

A Beckman Type R Dynograph was used to 

record the psychophysiological variables. Palmar 

skin conductance, heart rate, and respiration were 

measured. Heart rate was obtained from chest 

electrodes with leads connected to a cardiotachometer. Skin resistance was recorded from 

zinc-zinc sulphate electrodes attached to the 

palmar and dorsal surfaces of the left hand. The 

transducer for measuring respiration consisted 

of a thin mercury-in-vinyl tube. The ends of the 

tube were attached to Velcro bands and positioned on the S at the base of the rib cage. The 

mercury belt formed one of the arms of a bridge 

circuit. 

C. P1·oce d~tre. Upon arriving for the experiment, the S was given a modified version of a 

scale which had been employed in several previous 

studies.18 22 The questionnaire contained 23 

statements describing potentially "stressful" situations. The S rated, on a seven-point scale, the 

degree to which he felt each situation would 

bother him. To minimize association between 

the questionnaire and the experiment, the S was 

not told that the questionnaire was relevant to 

the present experiment, and one experimenter 
Following completion of the questionnaire, 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 40 

minutes. To prevent the S's knowing that the 

task was almost over, the experiment was stopped 

after 25 rather than 40 minutes. At this time 

the E went into the experimental room, removed 

the electrodes, and asked the S to complete a 

post-experimental questionnaire. 

D. Scoring of Data. Each S's mean score on 

five items contained in the pre.experimental 

questionnaire was used as the basis for assignment to either a "high distractibility" (HD) or 

"low distractibility" (LD) group. The assignment was made by ranking the scores from highest to lowest and splitting the distribution at the 

median. 

The items used were as follows : 

(a) Listening to a lecture when the people 

behind you are talking. 

(b) Trying to concentrate with a faucet 

dripping. 

(c) Deeply engrossed in trying to figure out 

a problem when someone turns on the radio 

full-blast. 

(d) Studying or trying to concentrate on an 

important assignment in a room with flickering 

· overhead lights. 

(e) Studying for an important final exam 

with people standing around talking loudly. 

The performance data were machine-analyzed 

and the following data obtained for each S for 

each successive one-minute period of the session. 

(a) Mean response time. 

(b) Standard deviation of response time. 

(c) Single longest (maximum) response 

time. 

(d) Single shortest (minimum) response 

time. 

(e) Number of incorrect responses. 

3 

the beginning and end of the test session. Ea

respiration cycle occurring in the one-min

scoring segments was measured from inspirati

to inspiration and means and standard deviatio

obtained. Heart rate and heart-rate variabil

were obtained from the cardiotachometer tr

mgs. Skin resistance was measured at the 

ginning and end of the one.minute periods, t

values cmwerted to conductance, and mea

computed. 

III. Results. 

Although it was intended to analyze perfor

ance changes oyer successive one-minute perio

examination of the data suggested that the u

of larger time intervals would increase the s

bility of the measures. Consequently, the d

were combined into four-minute periods. T

procedure was followed for all performan

Yariables. 

Figure 1 shows mean response time across t

six periods for the HD and LD groups as w

as the data for both groups combined. Exa

ination of this figure re,·eals a clear separati

between the HD and LD groups, with the lat

group displaying the faster . response time. 

repeated measures analysis of Yariance yield

significant F-values for both groups (F=5.7

df = 1.48; p < .05) and periods ( F = 2.25; d

5,240; p = .05). There was no significant int

action. Tukey's HSD testl 5 was used for in

vidual comparisons between periods. Only 

increase in response time bet\yeen periods I a

0 .82,.... 

IJ) 

~ 0 .80 f- (f) 

E 78~ 

1-

cv 

IJ) 0.76 f- c: 

0 

a. 

IJ) 

cv 0 .74f- a::: 

I>< 

FIGURE 1. 

I 

I 

H

T

~ ...n L

I I I I I 

n m Ill: :2: JZI 

Periods 

l\Iean response time across periods. 
nonsignificant (p > .05). 

Figure 2 shows response-time variability. Although there is a general increase in variability 

during the experimental session, this increase appears to be primarily a reflection of an increase 

in the HD group, i.e., after a general rise in 

variability from period I to II, variability of 

the LD Ss remains fairly constant while that of 

the HD Ss continues to increase. The analysis 

of variance revealed the overall difference be· 

tween groups to be nonsignificant (F=2.98; 

df=1,48; p>.05), but did reveal a significant 

difference between periods (F = 11.27; df = 5,240; 

p<.001) and a significant interaction (F=2.58; 

df=5,240; p<.05). 

0.240 

"' 0.230 Q) 

E 0.220 

IQ) 0.210 

"' c 0.200 0 

g. 0.190 Q) 

a: 0. 180 

-0 0.170 

~ 0.160 

1>< 0.( !50 

HD 

Total 

LD 

Periods 

FIGURE 2. Standard deviation of response times across 

periods. 

In examining this interaction, tests of simple 

effects of groups revealed the differences between 

groups to be significant at periods V (F=6.96; 

df=1,288, p<.01) and VI (F=4.16; df=1,288; 

p< .05), but not at periods of I, II, III, or IV. 

While tests of simple effects of periods revealed 

the differences bet\veen periods to be significant 

for both the HD (F=10.38; df=5,240; p<.001) 

and the LD (F=3.46; df=2,240; p<.01) groups, 

further comparisons using Tukey's HSD test, 

showed the significant period effect obtained for 

the LD group was a result of the increase between periods I and II (p<.05). There were no 

significant differences between any of the other 

periods for this group. These results support 

the impression gained from Figure 2 of an initial 

increase in variability for both groups which 

4 

Q) HD en 

~ 

Q) 

E 

1- Total 

Q) 

"' c 

0 

0. LD "' Q) 

a:: 

E 

::l 

E 

)( 1.40 0 

~ 

I>< 

I li m 

Periods 

FIGURE 3. Maximum response times across periods. 

levels off after period II for the LD Ss, but 

continues to increase for the HD Ss. 

To gain further information regarding the 

nature of this increase in variability, the mean 

maximum and minimum response times in each 

block were plotted. These are shown in Figures 

3 and 4 for maximum and minimum response 

times respectively. 

The similarity between the trends displayed in 

Figures 2 and 3 is readily apparent, and the 

results of the analysis of variance performed on 

the maximum response times are essentially the 

same as those obtained for the variability data. 

Thus, the difference between groups was nonsignificant ( F = 3.65; df = 1,48; p > .05), but there 

was a significant difference between periods 

(F=8.43; df=5,240; p<.001) and a significant 

interaction ( F = 2.40; df = 5,240; p < .05). Tests 

of simple effects also revealed results which were 

comparable to those obtained for response variability. There were significant differences between the two groups at periods V (F=7.82; 

df=1,288; p<.01) and VI (F=4.45; d£=1,288; 

p < .05), but no differences bebYeen groups at 

periods I, II, III, or IV. Simple effects of 

periods revealed a significant difference between 

periods for the HD Ss (F=8.19; df=5,240; 

p<.001) but not for the LD Ss (F=1.29; 

df=5,240; p>.25). 

Since maximum response times increased significantly during the session while mean response 

times remained relati Yely constant, minimum 

response times would be expected to show a 
p

g

The analysis of variance revealed the overall decline to be significant ( F = 3.82; df = 5,240; 

p <.01), with LD Ss having faster minimum 

response times than HD Ss (F=4.49; df=1,48; 

p < .05). There was no significant interaction 

(F<l.OO), indicating that the decline was comparable for both groups. 

.,; 0.55 (.) 

Q) 

(/) 0 .54 ~ 

Q) 0 .5:3 

E HD i= 0 .52 

Q) 0.51 fJ) 

c: Toto I 0 

0. 

fJ) 0.49 LD <I> 

a:: 

E 

:l 

E 

c: 

~ 

IX I n: m :nz: :sz: :sz:I 

Periods 

FIGURE 4. Minimum response times across periods. 

was significant (F=12.02; df=2,240; p<.0

These data, as shown in Figure 5, also sugge

possible difference between groups with the 

Ss making the greate1· number of errors. 

difference between groups, however, did 

reach significance (F=2.78; df =1,48; p>.

and there was no significant interaction (

1.00). 

1:3. 6 L

12.8 

12 .0 fJ) 

.... 

0 1 1.2 T

.... 

.... 

w 10.4 

-0 9 .6 

.... 8 .8 <I> H

.D 

E 8 .0 :l 

z 7 .2 

IX 6 .4 

5 .6 

I n: m :nz: ::2: 3ZI 

Periods 

FIGURE 5. Frequency of errors across periods. 

TABLE 1 . 

Mean values obtained for each physiological variable at 

the beginning and end of the experimental session. 

Variable Group Beainni!!l ~ Difference F* 

HD 71 .03 72.56 

HR (bpm) LD 76.58 77.94 

Total 73.81 75.25 1.44 0.04 N

HD 3.28 4.69 

HR. SD (bpm) LD 3.73 4.55 

Total 3.51 4.63 1.12 10 .85 < 

Conductance (micromhos) HD 11.34 10.75 ·LD 10 .23 9.49 

Total 10.78 10.16 - . 62 15.76 < 

Reap. Pd. (sees) HD 2.99 3.67 

LD 2.93 3.67 

Total 2.96 3.67 0.71 13.42 <. 

Reap. Pd. SD {sees) HD 0. 39 1.13 

LD 0.34 1.10 

Total 0.36 1.12 0.76 19.04 < 

* Only the F-values for the overall between-periods effect are given since none of the other comparison

were significant {R >.05). 

5 
period of task performance, repeated measures 

analyses of variance were performed on each of 

the measures obtained at the beginning and end 

of the session. For none of the measures (heart 

rate, heart-rate variability, respiration period, 

respiration-period variability, and skin conductance) was a significant difference obtained between the HD and LD groups. 'With the exception of the F-value for the heart rate analysis, 

which was 2.80 (df=1,48; p>.05), all the remaining between-group comparisons had Fvalues of less than 1.00. Likewise, all of the 

interactions "·ere nonsignificant ( F < 1.00). All 

of the F-values obtained for the between-periods 

comparisons, however, with the exception of 

heart rate were significant. These values along 

with the means for the two groups on each variable are shown in Table 1. 

Respiration period, respiration-period variability, and heart-rate variability inc1'eased during the session while conductance decreased and 

heart rate remained unchanged. 

IV. Discussion. 

The results of the present study indicate that 

individuals who rate themselves as high in susceptibility to distraction are not only slower in 

their overall rate of responding than low-distractibility subjects, but are apparently less able 

to maintain a uniform rate of responding under 

monotonous conditions. Response times of the 

HD Ss showed a progressive increase in variability over the session, while performance variability of the LD Ss remained essentially 

constant. 

Examination of maximum and minimum response times revealed the increased variability 

of the HD Ss to be primarily a reflection of distributions increasingly skewed in the direction 

of lengthened response times. An increase in 

frequency or duration of "long response times" 

has frequently been reported in studies of prolonged performance on serial reaction tasks, and 

this phenomenon has been hypothesized to be a 

reflection of a progressive decline in attention.H 

Since it was the HD Ss who displayed increasingly long gaps or pauses, the results would 

appear to support the hypothesis that the observed decrement was the result of an inability 

6 

cannot be entirely ruled out, if the decrement 

were the result of this alone, one might have 

expected the LD Ss, with their higher rate of 

responding, to show the greater rate of increase 

in long response times. 

While a measure of extroversion was not obtained in the present study, there are reasons for 

suspecting the existence of a relationship between 

susceptibility to distraction and extroversion. 

Distractibility is believed to be related to impulsivity14 and impulsivity is known to be a 

prinicple dimension of extroyersion. 25 Also, 

there are certain similarities between the results 

obtained for HD Ss in the present study and 

those obtained for extroverts in several studies 

relating extroversion to serial reaction performance. Corcoran5 found extroverts to make fewer 

responses than introverts and to have more frequent gaps (long response times) . Claridge4 

reported a similar relationship between speed of 

responding and extroversion among psychoneurotics. Long response times were not examined in this study. 

Although daydreaming tendency has been 

shown by Antrobus, Coleman, and Singer1 to be 

related to performance decrement on another 

type of task requiring sustained attention ( auditory vigilance), it is not clear whether the measure of daydreaming tendency employed in the 

above study would be positively correlated with 

distractibility as measured in the present investigation. Indeed, in a factor analytic study of 

cognitive and personality variables, Singer and 

Antrobus20 found either no relationship or a 

negative relationship between measures of daydreaming and both extroversion and distractibility. While both tendency toward daydreaming and distractibility appear related to performance decrement under monotonous conditions, 

the attentional mechanisms involved may be 

quite different. 

Frequency of errors increased steadily in the 

present study, but no significant differences between HD and LD Ss were obtained. It is 

interesting to note that extroversion-introversion 

has not been found to relate to frequency of 

incorrect responses on this type of task either. 

5 

While it has been noted that errors tend to increase immediately prior to a block or gap, implying a relationship to lapses of attention,3 it 
when Ss attempt to perform a serial reaction 

task too rapidly. 23 The present data were examined with reference to the degree of relationship 

between number of errors, minimum response 

time, mean response time, maximum response 

time, and response variability. The obtained correlations between errors and each of these measures of response time were -.53 (p<.Ol), -.33 

(p<.05), -.09, and .04 respectiYely. The fact 

that the largest correlation was obtained "·ith 

minimum response time provides support for the 

obsenation that errors in this type of task appear to be associated with high rates of responding. There was no evidence of any relationship 

bet\Yeen errors and either mrtximmn response 

time or response Yrtriability. 

The lack of relationship between self-mted 

distractibility and either leYels or change in any 

of the psychophysiological measures was unexpected. Distractibility in children is believed to 

be related to highly Yrtrirtble heart mtes and 

respiration rates14 and simibr relationships were 

expected for HD Ss in the present study. The 

changes which occurred in the present study for 

all variables except heart rate were in directions 

which previous research has suggested may accompany declining Yigilance or attention. To 

the extent that HD Ss were less able to sustrtin 

attention than LD Ss, it is somewhat surprising 

that this was not reflected in a correspondingly 

greater rate of change in these physiological 

measures. Perhaps one possible explanation for 

the lack of relationship was in the relatively 

brief measurement periods employed for the 

psychophysiological variables, which, because of 

sampling error, could obscure individual differences. Unfortunately, the length of the measurement periods was largely dictated by the difficulties involved in handscoring large quantities 

of hea:rt-rate variability data. A follow-up 

study now in progress will employ computer processing and analysis of the heart-rate variability 

7 

g

ment periods distributed throughout the t

sesswn. 

V. Summary. 

In summary, the results of this study indic

that individuals who rate themselves as s

ceptible to distraction in their daily lives find 

difficult to sustrtin rtttention when required 

perform a monotonous task demanding contin

ous attention. The obtrtined decrement took t

form of increasingly long grtps or pauses in p

formance which became quite evident after a

proximately 20 minutes of performance. 

contrast, individuals rating themselves low 

distractibility were able to perform the task in 

superior manner with no evidence of a decline 

attention. Other studies of performance und

monotonous conditions haYe found similar d

ferential patterns of decrement for subje

differinrr in extroYersion-introyersion and ten

"' ency to daydream. Taken together with t

present results, these findings clearly sugg

that certain temperamental and cognitive va

ables are significantly related to performan

decrement under minimal task-load conditio

\Vhat the pattern of interrelationships is betwe

these variables and which may be the best p

dictors of performance decrement under the

conditions remains to be empirically determine

Although most of the physiological variab

showed progressiYe and significant changes 

directions that previous research has suggest

should reflect declining attention, none of the

variables was significantly related to self-rat

susceptibility to distraction. Research in p

gress, using a computer to assist in processi

the laro-e amounts of psychophysiological da

"' 

generated, will enable a more adequate determ

nation of the extent to which such measures 

heart-rate and respiration-rate variability refl

differential changes in attention during mono

nous performance. 
REFERENCES 

1. Antrobus, J. S., n. Coleman, and J. L. Singer: 

Si~nal-DE'tPrtion PE-rformance h~· ~ubjects Differin~ 

in Predisposition to DaydrE-aming, JOUR::\'AL OF 

COXSULTIXG PSYCHOLOGY, 31 :4i\7-4Dl, J9G7. 

2. Bakan, I'., .T. A. Relton, and .J. C. Toth: ExtroversionIntroversion and Decrement in an Auditory Vigilance 

Task. In D. N. Buckner and J. J. :ucGrath (Eels.), 

Vigilance: A Symposium, New York, i\lcGraw Hill, 

1963, 23-33. 

3. Bertelson, P., and R. Joffe: Blocking::; in Prolonged 

Serial Responding, ERGO::\'O~ncs, G :109-llG, 19G3. 

4. Claridge, G. S. : Pc1·so1wlity and Arousal, Lonclon, 

Pergamon Press, 1967, G5-7i:i. 

5. Corcoran, D. W. J.: Personality and the InvC'rtf'd-t: 

Relation, BRITISH JOURNAL OF PSYCHOLOGY, 

56:267-273, 1965. 

6. Davies, D. R.: i\lonotony and Work, SCIE:\'Cl·J 

JOURNAL, 6 :26-31, 1970. 

7. Davies, D. R., and G. n. J. Hocl>ey: The Effects of 

Noise and Doubling the Signal Frequency on Individual Differences in Visual Vigilance Performance, 

BRITISH JOURNAL OF PSYCHOLOGY, l37 :381-

389, 1966. 

8. Davies, D. R., and G. S. Tune: Human Vigilance 

Pertonnance, New York, American Elsevier Publishing Company, Inc., 1969. 

9. Dobbins, D. A., J. G. Tiedemann, and D. M. Skordahl: Vigilance Under Highway Driving Conditions, 

PERCEPTUAL AND MOTOR SKILLS, 1G :38, 1963. 

10. Eysenck, H. J.: The Biological Basis ot Pcnonality, 

Springfield, Illinois, Charles C. Thomas, 1967. 

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

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

12. Flinn, D. E.: Functional States of Altered Awareness During Flight, AEROSPACE l\IEDICINE, 

36:537-544, 1965. 

13. Hopkin, V. D.: Human Factors in ATC. In Swedish 

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

Sweden, 12-14 March 1969, Proceedings. Stockholm, 

Swedish Society of Aeronautics and Astronautics, 

1970, 329-339 and 341-344. 

14. Kagan, J., and B. L. Rosman: Cardiac and Respiratory Correlates of Attention and an Analytic Attitude, JOURNAL OF EXPERIMENTAL CHILD 

PSYCHOLOGY, 1 :·50-63, 1964. 

8 

15. Kirk, n. E.: Experimental Design: P1·oced1tres tor 

the Behavioral Sciences, Belmont, California, 

Brooks/Cole, 1968. 

16. Lacey, J. I.: Somatic Response Patterning and 

Stress: Some Revisions of Activation Theory. In 

l\I. II. Appley and n. Trumbull (Eds.) Psychological 

St1·css, New York, Appleton-Century-Crofts, 1967, 

14-42. 

17. l\Iackworth, J. F.: Vigilance and Habituation, Baltimore, Penguin Books, Inc., 1970. 

18. l'f'ar~on, n. \V., and H. I. 'l'hackray: Consistency of 

Performancf' Chang-e :mel Autonomic Hesponse as a 

Fnnc·tion of Exprf'~Sf'cl Attitmle Towarcl a Specific 

Stn·~~ Sitnat ion , PSYCTIOPIIYSIOLOGY, fi ::>Gl-riG8, 

1 !)70. 

1!). ShOJ', H. E., ami H. l. Thackray: A l'ro~ram of 

Research in "IIigh\\·ay II~·pnosb.; '': A I'reliminan· 

Report, ACCIDE:\'T A::\'ALYSIS AXD l'REVE:\'-

'l'ION, 2 :103-109, 1970. 

20. Singer, J. L., and J. S. Antrobus: A Factor-Analytic 

Study of Daydreaming and Conceptually-Related 

Cognitive and Personality Variables, PERCEPTUAL 

AND MOTOR SKILLS, 17:187-209, 1963. 

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

Accompanying Performance on a Perceptual-1\Iotor 

Task, FAA Office of Aviation Medicine Report No. 

69-8, 1969. 

22. Thackray, R. I., and D. W. Pearson: Effects of 

Cognitive Appraisal of Stress on Heart Rate and 

Task Performance, PERCEPTUAL AND 1\IOTOR 

SKILLS, 27:651-658, 19G8. 

23. Weaver, H. B.: A Study of Discriminative Serial 

Action: l\fanual Response to Color, JOURNAL OF 

EXPERil\fENTAL PSYCHOLOGY, 31:177-201, 1942. 

24. Welford, N. T.: Heart Rate Variability During Continuous Performance. Presented at a symposium on 

Psychophysiological Correlates of Unman Performan ce held during the annual meeting of the American Association for the Advancement of Science, 

Dallas, Texas, 29 December 1968. 

25. White, P. 0., l\L I. Soueif, and H. J. Eysenck: 

Factors in the Eysenck Personality Inventory. In 

H. J. Eysenck and S. B. G. Eysenck (Eels.) Personality Structure and Measurement, San Diego, 

California, Robert R. Knapp, 196(), 194-217. 
Federal Aviation Administration, Office of Aviation 

Medicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO PERFORMANCE 

DECREMENT ON A TASK REQUIRING SUSTAINED ATTENTION by Richard I. Thackray, 

Karen N. Jones, and n. l\fark Touchstone, July 1972, 

8 pp. Report No. FAA-AM-72-25. 

Increasing automation of air traffic control tasks may have 

the undesirable side effect of increased monotony as a result 

of the anticipated reduction in task demands. While the 

actual extent of increase in monotony resulting from such 

automation is not as yet known, it is known that performance 

during low task-load conditions is accompanied by declining 

attention. Since individuals who are unable to sustain attention under low task-load conditions would appear to be more 

likely to commit errors and less able to handle a sudden 

emergency situation, it would seem desirable to examine the characteristics of individuals unable to sustain attention under 

these conditions. In the present study, 50 subjects performed 

a monotonous, but perceptually demanding task, for approximately 30 minutes without rest. It was .found that highI. Thackray, R. I. II. Jones, K. N. III. Touchstone, R. l\f. Descripto1·s Attention Distractibility Monotony Vigilance Federal Aviation Admini

Medicine, Civil Aerome

City, Oklahoma. SELF

TRACTIBILITY AS RELA

DECREMENT ON A T

TAINED ATTENTION 

Karen X Jones, and n. l

8 pp. Report No. FAA-A

Increasing automation of 

the undesirable side effec

of the anticipated reduc

actual extent of increase 

automation is not as yet 

during low task-load con

attention. Since individu

tion under low task-load 

likely to commit errors 

emergency situation, it w

characteristics of individu

these conditions. In the 

a monotonous, but percep

mately 30 minutes witho

------------------------------"""------------------------------------------------------------------------------------------------------------------ -- --- --

distractibility subjects (as determined from a questionnaire 

administered prior to the experiment) showed increasing 

lapses of attention during performance, while low-distractibility subjects failed to show any evidence of a decline in attention. Significant changes "·ere obtained for respiration, 

respiration-period variability, heart-rate variability, and skin 

conductance during the task period, but the magnitude of 

these changes did not differ among the two distractibility 

groups. 

distractibility subjects (

administered prior to t

lapses of attention during 

ity subjects failed to sho

tion. Significant chang

respiration-period variabi

conductance during the 

these changes did not d

groups. 
Federal Aviation Administration, Office of Aviation 

Medicine, Civil Aeromedical Institute, Oklahoma 

City, Oklahoma. SELF-ESTIMATES OF DISTRACTIBILITY AS RELATED TO PERFORMANCE 

DECREMENT ON A TASK REQUIRING SUSTAINED ATTENTION by Richard I. Thackray, 

Karen N. Jones, and R. Mark Touchstone, July 1972, 

8 pp. Report No. FAA-AM-72-25. 

Increasing automation of air traffic control tasks may have 

the undesimble side effect of increased monotony as a result 

of the anticipated reduction in task demands. While the 

actual extent of increase in monotony resulting from such 

automation is not as yet known, it is known that performance 

during low task-load conditions is accompanied by declining 

attention. Since individuals who are unable to sustain attention under low task-load conditions would appear to be more 

likely to commit errors and less able to handle a sudden 

emergency situation, it would seem desirable to examine the 

characteristics of individuals unable to sustain attention under 

these conditions. In the present study, 50 subjects performed 

a monotonous, but perceptually demanding task, for approximately 30 minutes without rest. It was ..found that highdistractibility subjects (as determined from a questionnaire 

administered prior to the experiment) showed increasing 

lapses of attention during performance, \Yhile low-distractibility subjects failed to show any evidence of a decline in attention. Significant changes were obtained for respiration, 

respiration-period variability, heart-rate variability, and skin 

conductance during the task period, but the magnitude of 

these changes did not differ among the two distractibility 

groups. 

I. Thackray, 

R.I. 

II. Jones, K. N. 

III. Touchstone, 

R. M. 

Descripton 

Attention 

Distractibility Monotony Vigilance 

Federal Aviation Admini

Medicine, Civil Aerome

City, Oklahoma. SELF

TRACTIBILITY AS RELA

DECREMENT ON A T

TAINED ATTENTION 

Karen N. Jones, and R. M

8 pp. Report No. FAA-A

Increasing automation of 

the undesirable side effec

of the anticipated reduc

actual extent of increase 

automation is not as yet k

during low task-load con

attention. Since individu

tion. under low task-load 

likely to commit errors 

emergency situation, it w

characteristics of individu

these conditions. In the 

a monotonous, but percep

mately 30 minutes witho

distractibility subjects (a

administered prior to t

lapses of attention during 

ity subjects failed to sho

tion. Significant chang

respiration-period variabi

conductance during the 

these changes did not d

groups.