Because of the large sample size employed in the above study, the statis-
tical likelihood that these data are the result of chance factors would
appear to be rather low. Consequently, their findings strongly suggest the
possibility that a small but significant superiority of men may exist in the
performance of simple vigilance tasks. However, even if a replication cf
this study verified these findings, this would not necessarily imply that
significant sex differences would be expected in complex monitoring perform-
ence. Kibler (&) has convincingly argued that complex mon‘toring tasks differ
in so many respects from simple vigilance viasks, that to generalize without
verification from simple to complex monitoring performance is unwarranted on
the basis of our existing lack of knowledge concerning the degree of rela-
tionship between performance on these two "types" of tasks.

The intent of the preseni study, then, was to determine whether men and
women differ in the ability to sustain attention during performance of a
complex monitoring task. The task was designed to approximate a futuristic,
highly automated ATC system in which the observer monitored alphanumeric
symbols for infrequent but “critical” changes. Performance was measured in
terms of latency toe detect these stimulus changes. In addition to measuring
mean latency, maximum and minimum latencies were also obtained. The results
of several nrevious studies of complex monitoring (5,13,14) suggest that
Maximum latencies reflect lapses of attention or failures to maintain scan-
ning, while minimum latencies provide an estimate of the individual's maximal
state of alertness at any given period during the course of a monitoring
session. It seemed desirable to include these measures elong with mean
latency in order to more completeJy assess possible sex differences in
performance.

Ii. Method.

Subjects. Twenty-six men and twenty-six women served as subjects (S).
All were selected from the general population (e.g., college students, house-
wives) and were paid for their participation. Their ages ranged from iS to
29 years. None had any prior experience with the task used nor did any have
any training in air traffic control.

Apparatus and Task Design. All task programing and recording of responses
were accomplished vy using a Digital Equipment Corporation (DEC) PDP-11/40
computer. The computer was interfaced with a VT-11 (DEC) 17-inch cathode-ray
tube (CRT), which served as the S's display. The CRT was located in a
console resembling an air traffic control radar unit. The stimuli (targets)
consisted of small rectangular "blips" representing the locations of given
aircraft. Adjacent to each target was an alphanumeric data block. Data
blocks comprised two rows of symbols: the top row, consisting of two letters
and three iwmerals, identified the aircraft, while the bottom row of six
numerals indicated its altitude and speed. The first three of these numerals
gave altitude in hundreus of feet and the last three gave groundspeed. For
a given target, the alphanumerics identifying the aircraft and its altitude
and groundspeed, as well as its entry and exit points, were randomly deter-

?


Studies are needed in which the same individuals are compared in their
performance on both simple and complex monitoring tasks. Such studiés have
apparently aot been conducted. However, a recent factor analytic analysis of
complex performance data has revealed that performance of simple monitoring
tasks loads on one factor when these tasks are performed in isolation, but on
a different factor when the S must engage in scanning and time sharing with
other tasks (4). While this evidence does not provide a completely satis-
factory answer to the question of the degree of relationship between perform-
ance of simple and complex monitoring tasks, it does suggest the possibility
that the two tasks may require quite different abilities. Thus, while the
present study found no evidence of sex differences in complex monitoring, this
does not necessarily preclude the possibility that such differences may exist
in the performance of simple vigilance or monitoring tasks. Further research
would be required to clearly determine whether sex differences exist in
simpie vigilance performance. The intent of the present study was to
examine possible sex differences only as they might apply to complex
monitoring performance.

With regard to the overall performance changes common to both sexes, the
results appear to reflect a general decline in arousal level. (An earlier
study (14) using the same task conditions revealed performance decrement to
be accompanied by a progressive increase in frequency of partial eye
closures, along with a decrease in heart rate, palmar skin conductance level,
and blood pressure.) This apparent decline in arousal affected all three
measures of detection latency, while in our previous study, only maximum and
mean latencies showed a significant increase. Since a larger sample was
employed in the present study, it is likely that the design used in the
earlier one lacked sufficient power to detect the low magnitude changes
obtained for minimum latencies.

Studies by Kogi and his associates (7,8) have demonstrated that regular
fluctuations of alertness normally occur in tasks requiring sustained visual
attention, and that these fluctuations may become more pronounced under
conditions producing monotony and drowsiness. Presumably, the increase in
range (maximum-minimum) of detection latencies during task performance in the
present study was a manifestation of a progressive increase in the amplitude
of these fluctuations in alertness. Whether this affected scanning frequency,
attentiveness, or some combination of both is a question which will be
addressed in future planned research.

I


Figure 1. The simulated air traffic control console with
a typical stimulus pattern. Only the lower
left button was used.

Mean response latency to critical stimuli correctly identified.
Single longest latency to a correctly identified criticai stimulus.
Single shortest latency to a correctly identified critical

Number of button presses without a critical stamulus.
Number of critical stimuli missed.

Number of light pen hits to a critical stimulus without a
button press.

eee ee ee
SOL LG

&

lil. Results.

Figure 2 shows mean detection latencies for ail critical stimuli, as well
as mean longest and shortest latencies, for both men and women. Analyses of
variance applied to these three sets of data revealed significant main effects
for the four 1/2?-hour veriods for mean latencies, F(3/150) = 9.52, p< -01,
maximum iatencies, F(3/150} = 5.05, p < .@1, and minimum latencies, F(3/150) =
4,02, p < .01. Nain effects for sex were not significant (p > .19) for any

of the three response measures, nor were any of the sex-by-pericds interactions

£


mined except for the following restrictions: (i) altitudes had to fall
within the range of 180 to 600 (in hundreds of feet): (ii) groundspeeds had
to fall within the range of 400 to 580 (in knots); and (iii) the entry and
exit points for a given target could not be separated by less than 30° along
the circumference cf the simulated redar screen.

At the beginning of an experimental session, the screen contained 16
targets. A simulated radar sweepline made one complete clockwise revolution
every 6 seconds. A target was updated as to location and any ci:ange in its
data block moments after the sweepline passed the target's prior location.
Targets normally moved in a lineas fashion unless a course change was
programed to avoid target overlaps. The overali impression was one of a
pattern of targets moving in discrete jumps as the sweepline passed. This
movement approximates very closely the way in which targets are updated in
contemporary air traffic control radars with computer-generated alphanumeric
displays. The critical stimulus or signal to which the S was instructed to
respond consisted of 992 appearing in the altitude block. Ten such critical
stimuli appeared in each 1/2-hour period; five occurred in the first 15
minutes and five in the second. The mean intersignal interval was 3 minutes.
Time of critical stimulus occurrence and the target in which it occurred were
randomly determined with the restriction that two targets could not contain
critical stimuli at the same time. The S's response to a critical stimulus
consisted of pressing a button located on the console and then holding a
light pen over the critical target. The light pen caused the altitude
portion of the data block to revert to its previous value. If the S failed
to detect a critical stimulus within 1 minute, the data block automaticaily
reverted to its previous value.

The computer and other recording apparatus were located in an adjacent
room from which the S was visible through a one-way mirror. Indirect lighting
was used in the S's room, and the level of illumination at the display was 2
foot-candles. TRis level approximates that used in operational air traffic
control environments. figure 1 shows the S's console with a typical stimulus

pattern displayed on the CRT.

Procedure. On arrival the S was taken to the testing room and given
orientation instructions. The task instructions emphasized the necessity of
pressing the button immediately on detection of a critical stimulus. The S
was Cold thet the critical stimulus represented some form of malfunction not
detected by the computerized radar system. Following the taped instructions,
the S was given a 3-minute practice period containing three critical stimuli.
After the practice perio.! the ?-hour test period was initiated. Personal
timepieces were taken from the S before the test period began.

Neasurenent of the Performance Data. Performance data were computer
processed and the following measures shown below were obtained on each S for
each 30-minute period. (Ali latency measures refer to the time from critical
stimulus onset te the button press.)



22r
20F
18- oO Maximum Latencies
[6b
o Ih
a
Z l2Pr
°
8 tor Mean Latencies
o
8 he oo
——___ -—__e——
ek
4b Minimum Latencies
2b w tt a —<«
oul L J}

i
2 3 4
30-MINUTE PERIODS

Figure 3. Mean, maximum, and minimum detection latencies
for the combined groups.

stimuli were not detected, there were no errors of commission (responses to
noncritical targets), and there was only one errer of procedure. (A light
pen confirmation was made without a preceding button press.)

Iv. Discussion.

Both sexes showed significant increases during the session in alli latency
measures. However, trxere was nc evidence of any difference between men and
women in either the magnituce or pattern of change in any of the three
measures used. Errors of omission, commission, and procedure were too few in
number to allow any sex comparisons.

Although Waag et_al. (16) found men to be significantly superior to women
in the performance of a simple visual vigilance task, their results are not
necessarily in conflict with the findings of the present study. As noted
earlier, complex visual monitoring tasks differ in many respects from simple
vigilance tasks. At the very least, the former tasks involve a scanning
factor in addition to the basic alertness factor involved in simple vigilance
performance. On the basis of our present knowledge, there is no reason to
assume that both types of tasks would require the same skills or abilities.



FAA-AM. 78411

s

A COMPARISON OF THE VIGILANCE PERFORMANCE OF
MEN AND WOMEN USING A SIMULATED RADAR TASK

Richard I. Thackray
R. Mark Touchstone
3. Powell Bailey
Civil Aeromedical Institute
Federal Aviation Administration
Oklahoma City. Oklahoma

March 1978

Document is available to the public through the
National technical Information Service,
Springfield, Virginia 22161

Prepared for
U.S. DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Office of Aviation Medicine
Washington, D.C. 20591

yy


Thackray, R. I., K. N. Jones, and R. M. Touchstone: Personality and
Physiological Correlates of Performance Decrement o1.a Monotonous: Task
Requiring Sustained Attention, BRITISH JOURNAL OF PSYCHOLOGY,
65:351-358, 1974.

Thackray, R. i., 3. P. Bailey, and R. M. Touchstone: Physiological,
Subjective, and Performance Correlates. of Reported Boredom aad
Monotony While Performing a Simulated Radar Control Task. In

R. R. Mackie (Ed.), Vigilance: Theory, Operational Performance, and
Physiological Correlates, Plenum Publishing Company, New York, 1977,
pp. 203-215.

Thackray, R. I., J. P. Bailey, and R. M. Touchstone: The Effect of

Increased Monitoring Load on Vigilance Performance Using a Simulated
Radar Display. FAA Office of Aviation Medicine Report No. AM-77-18,
1977.

Telin, P., and P. G. Fisher: Sex Differences and Effects of
Irrelevant Auditory Stimulation on Performance of a Visual Vigilance
Task, PERCEPTUAL AND MOTOR SKILLS, 39:1255-1262, 1974.

Waag, W. L., C. G. Halcomb, and D. M. Tyler: Sex Differences in
Monitoring Performance, JOURNAL OF APPLIED PSYCHOLOGY, 58:272-274, 1973.

Whittenburg, J. A., S. Rose, and T. G. Andrews: Sustained Perceptual
fficiency as Measured by the Mackworth "Clock" Test, PERCEPTUAL AND
MOTOR SKILLS, 6:109-115, 1956.


jn
°

il.

References

Coules, 3., and D. L. Avery: Human Performance and Basal Skin
Conductance in a Vigilance-Type Task With and Without Knowledge of
Results, PERCEPTUAL AND MOTOR SKILLS, 23:1295-1302, 1966.

Davis, D. R., and G. S. Tune: Human Vigilance Performance, New York,
American Elsevier Publishing Company, Inc., 1969, pp. 127-129.

Hardesty, D., D. Trumbo, and W. Bevan: Influence of Knowledge of
Results on Performance in a Monitoring Task, PERCEPTUAL AND MOTOR SKILLS,
16:629-634, 1963.

Jennings, A. E., and W. D. Chiles: An Investigation of Time- Sharing
Ability as a Factor in Complex Performance, HUMAN FACTORS, 1977, In
Press.

Johnston, W. Av, W. C. Howell, and I. L. Goldstein: Human Vigilance as
a Function of Signal Frequency and Stimulus Density, JOURNAL OF
EXPERIMENTAL PSYCHOLOGY, 72:736-743, 1966.

Kibler, A. W.: The Relevance of Vigilance Research to Aerospace
Monitoring Tasks, HUMAN FACTORS, 7:93-99, 1965.

Kogi, K., and T. Ohta: Incidence of Near Accidental Drowsing in
Locomotive Driving During a Period of Rotation, JOURNAL OF HUMAN
ERGOLOGY, 4:65-75, 1975.

Kogi, K., and Y. Saito: Rhythmic Fluctuation of Orientation to a
Continuous Manual Control Task, JOURNAL OF HUMAN ERGOLOGY, 2:169-184,
1973.

NeCormack, P. D.: Performance in a Vigilance Task as a Function of
Length of Inter-Stimulus Interval, CANADIAN JOURNAL OF PSYCHOLOGY,
4:265-265, 1960.

Smith, R. L., L. F. Lucaccini, and M. H. Epstein: Effects of Monetary
Rewards and Punishments on Vigilance Performance, JOURNAL OF APPLIED
PSYCHOLOCY, 51:411-416, 1967.

Thackray, R. I., k. N. Jones, and R. M. Touchstone: Seif-Estimates of
Distractibility as Related to Performance Decrement on a Task Requiring
Sustained Attention, ERGONOMICS, 16:141-152, 1973.


22b
20
18 Maximum Latencies
16k
Dia o—%O Males
2 @—-@ Females
iol
S tab
Y Ok Mean Latencies
eb a
i
ee
4h Minimum Latencies
i
ar a ne
3 1 ! i J

i 2 3 4
30 - MINUTE PERIODS

Fiqure 2. Mean, maximum, and minimum detection latencies
for the two sex groups.

significant (p > .10). Since there were no significant interaction effects
and no differences between the two groups, the data were combined for cach of
the three measures. These data are shown in Figure 3.

Because the shape ef the curve for maximum latencies suggested a
possible departure from Jinearity, trend analyses were conducted on these
data, as well as on mean and minimum latencies. Significant linear components
were obtained for maximum, F(1/153) = 10.17, p < .01, imum, F(1/153) =
12.12, p < .O1. and mean F(1/153) = 5.59, p < .05 latencies. No quadratic or
cubic components were significant (p > .05).

The apparent increase, shown in Figure 3, in the range of latencies from
the beginning to the end of the session was tested for significance by
obtaining the difference between each S's maximum and minimum latencies for
each 1/2-hour period. An analysis of variance conducted on these scores
revealed that the differences between periods were significant, F (3/153) =
4.41, p< Ol.

As with the previous study in which this task was used (14), errors of
omission, commission, and procedure were almost nonexistent. Three critical


A COMPARISON OF THE VIGILANCE PERFORMANCE OF
MEN AND WOMEN USING A SIMULATED RADAR TASK

I. Introduction.

The increasing automation of air traffic control (ATC) systems is grad-
ually changing the role of the controller; he/she is becoming less of an
independent participant in traffic control and more of a monitor or overseer
of a complex computerized system. This gradual change in role places an
increasing premium on the ability to sustain a high, consistent level of
attention to a task in which the controller may intervene only occasionally.
Since individuals who find it difficult to sustain attention under decreased
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 those individuals who find it difficult to
sustain attention under such conditions. Much of our research over the past
several years has been directed toward this end (11,12,13).

Of the various subject variables or individual characteristics that may
relate to the ability to sustain attention during monitoring performance, sex
is one that has received relatively little direct attention (2). Davis and
Tune (2) suggest inat this lack of interest may be understandable, if it is
assumed that there are no good a priori reasons why sex differences should be
of any practical importance. At the present time, however, active programs
are underway in the FAA te recruit more women into ATC occupations, and it is
thus of practical importance to determine whether significant sex differences
do exist in the ability to effectively monitor increasingly automated radar
displays.

Those vigilance studies that have included sex as a variable have
employed relatively simple monitoring tasks and have generally considered sex
differences to be of secondary interest (1,3,9,10,15,17). Significant sex
differences, when obtained, are typically manifested as higher order inter-
actions with more primary task or environmental variables. Because of the
conflicting array of findings, it is difficult to arrive at any clear under-
standing of the influence of sex per se from these data.

Of the studies reviewed, apparently only one vigilance study has treated
sex as the single variable of interest. Waag, Halcomb, and Tyler (16) tested
220 men and an equal number of women on a simple visual monitoring task for a
period of 1 hour. Both sexes showed parallel declines in percent detection
over the task period, but men were significantly superior, F{1/438) = 15.76,
p< -001, to women in the percentage of signals detected for all time periods
examined. In terms of the overall magnitude of this difference, men
consistently detected about 10 percent more signals than did women.


Technical Report Documentation Page

jE. Revert Ne. 2. Government Accession No. 3. Recipient s Catalog No.

| FAA-AM-76-11

]

\E Title and Sobutte

A COMPARISON OF THE VIGILANCE PERFORMANCE OF MEN

So Report Bore

March 1978

: AND WOMEN USING A SIMULATED RADAR TASK in

> Pertorming Organization Code

18. Performing Organ:zation Report Ne.

asthor'ss Richard I. Thackray, R. Mark Touchstone, 1
and J. Powell Bailey i
t

9, Performing Organi zerion Neme ana Address

TO. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute

Contract or Grant No

| P.O. Box 25082 Ty
{ Oklahoma City, Oklahoma 73125

| 13. Type of Report end Period Covered
: Sponsoring Agency Nome ond Add-ess

Office of Aviation Medicine
Federal Aviation Administration H

S00 Independence Avenue, S.W. 3.
Washington, D.C. 20591

~ Sponsoring Agency Code

; 1S. Supplementary Nores

Work was performed under Task AM-C-77-PSY-~60 and Task AN-C-7S-PSY-60.

16. Abstract

The present study examined the question of possible sex differences in the ability
to sustain attention to a complex monitoring task requiring only a detection
response to critical stimulus changes. The visual display was designed to
approximate a futuristic, highly automated air traffic control radar display
containing computer-generated alphanumeric symbols. Twenty-six men and an equal
number of women were each tested over a 2-hour session. Sixteen targets appeared
on the screen at all times, with 10 signals (a designated change in the alpha-
numerics) randomly presented during each half hour of the test session.

Detection latency to the signals increased significantly during the session, but
there was no evidence of any significant difference between the sexes in the
magnitude or pattern of this increase. The results are discussed in terms of a
general decline in alertness that was apparently equal for both sexes.

i U7. Key Words 118. Distribution Statement

i Air Traffic Control Sex Differences { Document is available to the public
Attention Vigilance : through the National Technical Information
Automation | Service, Springfield, Virginia 22161
Monitoring i

; Performance j

F Security Clossif. (of this report) ] 20. Security Clessif. ‘of this page) ] 21 No. of Poses [220 Price

Unclassified | Unclassified ! 2

Form DOT F 1700.7 ¢-72:

Reproduction of completed page cuthorized

.


NOTICE

This document is disseminated under the sponsorship of the Department
of Transportation in the interest of information exchange. The

United States Government assumes no liability for its contents or use
thereof

Cre