F AA-AM-73-15 

SUSCEPTIBILITY TO ANXIETY AND SHIFT 

DIFFICULTY AS DETERMINANTS OF 

STATE ANXIETY IN AIR TRAFFIC 

CONTROLLERS 

Roger C. Smith, Ph.D. 

C. E. Melton, Jr., Ph.D. 

**FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma '73125 

December 1973 

Availability is unlimited. Document may be released 

to the National Technical In formation 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 
TECHNICAL REPORT STANDARD TITLE PAGE 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

FAA-AM-73-15 

4. Title and Subtitle 5. Report Date 

SUSCEPTIBILITY TO ANXIETY AND SHIFT DIFFICULTY AS December 1973 

DETERMINANTS OF STATE ANXIETY IN AIR TRAFFIC 6. Performing Organization Code 

CONTROLLERS 

7. Author! s) 8. Performing Orgoni zation Report No. 

Roger c. Smith, Ph.D. 

c. E. Melton, Jr •, Ph.D. 

9. Performing Orgoni zation Nome and Address 10. Work Unit No. 

FAA Civil Aeromedical Institute 

P. o. Box 25082 11. Contract or Grant No . 

Oklahoma City, Oklahoma 73125 

13. Type of Report and Period Covered 

12. Sponsoring Agency Nome and Address 

Office of Aviation Medicine OAM Report 

Federal Aviation Administration 

800 Independence Avenue, S .W. 14. Sponsoring Agency Code 

Washington, D. c. 20591 

15. Supplementary Notes 

This research was performed under Tasks AM-A-70-PSY-20, AM-A-71-PSY-20, 

AM-A-72-PSY-34, and AM-B-73-PSY-34. 

16. Abstract 

The State-Trait Anxiety Inventory (STAI) was used to assess the anxiety of air 

traffic controllers who had experienced difficult and easy work shifts. Eighty 

volunteers completed the STAI before and after two or more eight-hour work shifts. 

Controllers relatively high in anxiety proneness tended to report higher levels 

of anxiety in association with control work than those relatively low in anxiety 

proneness. The mean A-state score after shifts was higher than the mean score 

before shifts. It was also determined that the increase in anxiety during shifts 

was greater for difficult shifts. 

17. Key Words 18. Distribution Statement 

Anxiety Availability is unlimited. Document may be 

Air Traffic Controllers released to the National Technical InformaPerformance t ion Service, Springfield, Virginia 22151, 

Work Load for sale to the public. 

19. Security Classil. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 3 $3.00 

Form DOT F 1700.7 ca-ssl 
SUSCEPTIBILITY TO ANXIETY AND SHIFT DIFFICULTY AS 

DETERMINANTS OF STATE ANXIETY IN AIR 

TRAFFIC CONTROLLERS 

I. Introduction. 

In research on the affective responses of air 

traffic controllers,•.g., 2 4 it has been shown that 

controllers tend to be relatively low in such traits 

as anxiety proneness, at least in comparison to 

normal college undergraduate students. However, even though, as a group, controllers tend 

to be non-anxious, they still demonstrate significant increments in anxiety during air traffic 

work shifts. It was the purpose of this study 

to consider the effect of difficulty of work shifts 

on anxiety levels experienced by controllers during work periods, the expectation being that controllers should show significant increases in 

anxiety in association with shifts judged difficult, 

but not in those judged as easy shifts. It was 

also a concern of this study to determine the 

degree to which level of experienced anxiety in 

air traffic control work is a function of the relative susceptibility of controllers to experience 

anxiety. It was expected that controllers relatively high in trait anxiety (anxiety proneness 

or A-trait) would have higher levels of experienced anxiety during work shifts and would also 

show greater increments in anxiety during difficult shifts than controllers who are comparatively 

low in A-trait. 

II. Method. 

A. Subjects. A total of 81 controllers from 

three air traffic control facilities was surveyed. 

Each controller had volunteered to participate 

in a multidisciplinary study of physiological and 

psychological consequences of air traffic control 

work. 2 

B. Procedure. Each controller completed questionnaires before and after at least two regular 

eight-hour work shifts. On each of these occasions, the A-State Scale of the State-Trait Anxiety Inventory (STAI) 6 was administered to 

measure anxiety level at the moment. In addition, 

the controller answered the A-Trait Scale of the 

1 

STAI, which measures susceptibility or proneness 

to anxiety; the scale was completed before the 

first work shift under consideration. After each 

shift, in addition to the STAI A-State Scale, 

each controller rated the shift for difficulty. A 

five-point scale was used which required the controller to select the most descriptive terms for his 

shift from the alternatives of "very difficult," 

"difficult," "neither difficult nor easy," "easy," and 

"very easy." 

The controllers were divided into a High Atrait Group and a Low A-trait Group of 40 controllers each. The division was made on the 

basis of the scores obtained on the STAI ATrait Scale; controllers with scores above and 

below the median of 28.5 were placed into the 

High and Low groups respectively. One controller was deleted from the sample by random 

selection to provide an equal number of persons 

in each group. 

After assignment to one of the two A-trait 

groups, the controllers were further subdivided 

into Difficult Shift and Easy Shift Groups comprised of 20 individuals each. The assignment 

was made on the basis of the most extreme rating 

of shift difficulty made by each controller. This 

was done in order to maximize the differences in 

ratings between the two groups. Each controller 

was assigned to only one shift group because some 

individuals gave the same rating to all the surveyed shifts, and thereby eliminated the possibility for within-subject comparisons on this 

variable. Thus, if a controller was surveyed on 

three shifts and rated one "very difficult," one 

"difficult," and one "easy," he was assigned to 

the Difficult Group and the scores from the shift 

rated "very difficult" were used. If the controller 

made equally extreme "difficult" and "easy" ratings for different shifts (e.g., at least one shift 

rated "very difficult" and one rated "very easy"), 

the group assignment was determined by chance. 
If two or more shifts were given the same rating 

(e.g., two shifts judged "very difficult"), the 

shift used to provide the scores for analysis was 

determined by chance. Each controller contributed only the set of scores from one shift to 

the data analysis. 

III. Results. 

The mean A-Trait Scale score for the high 

A-trait controllers exceeded the mean for the 

controllers relatively low in A-trait as expected 

(Table 1) ; the difference was significant (p < .01). 

Similarly, the mean A-State Scale scores for 

these two groups (i.e., the overall mean score derived from all pre- and post-shift administrations 

of the STAI for high and low A-trait controllers) 

showed corresponding significant differences 

(p<.01). It should be noted that although normative data for normal adult groups are not 

available for the STAI, a comparison to college 

undergraduate norms indicates that the A-Trait 

Scale means correspond to the 40th and the 8th 

percentiles of the student group, respectively. 

Thus, even those controllers relatively high in 

A-trait do not tend to score as .high on the ATrait Scale (anxiety proneness) as the average 

college student. With respect to the A-State 

Scale, the means represent the 48th and 30th 

percentiles for college students, respectively. 

Thus, for both groups, A-state levels reported 

during control work were substantially higher 

than would have been predicted from the A-trait 

levels and approached average college student 

levels for the High A-trait Group. 

TABLE 1 

Mean A-Trait and A-State Scale raw scores for air 

traffic controllers relatively high and low in anxiety 

proneness (A-trait) . 

Group 

High A-trait 

Low A-trait 

A-Trait Scale 

33.37 

25.50 

TABLE 2 

A-State Scale 

34.61 

30.33 

Mean A-State Scale raw scores and mean differences in 

raw scores between the A-Trait Scale and the A-State 

Scale obtained prior to air traffic control work shifts 

for cnntrGllers relatively high and low in anxiety 

proneness (A-trait). 

Group 

High A-trait 

Low A-trait 

A-State Scale 

31.40 

27.85 

A-State-A-Trait 

-1.97 

+2.35 

2 

The responses of controllers to anticipation of 

air traffic control work also varied as a function 

of A-trait level (Table 2). Prior to working a 

shift, controllers relatively high in A-trait had 

lower A-state than A-trait scores (p<.01) while 

controllers low in A-trait had higher A-state than 

A-trait scores (p<.05). Thus, the prospect of 

undertaking an air traffic control work shift apparently tends to result in some energizing of 

anxiety for low A-trait controllers, while it 

tended to have a somewhat relaxing effect on 

controllers more prone to experience anxiety. 

Both the relatively high and low A-trait controllers reported significant (p<.01) increases in 

anxiety as a function of completing a work shift 

(Table 3). This increment in anxiety from before to after shifts also varied as a function of 

the judged difficulty of the shift as indicated by 

the significant (p<.01) interaction between these 

two variables. Thus, while both the Difficult and 

Easy Shift Groups showed a significant (p<.01) 

increase in A -state across shifts, the increase was 

significantly greater (p < .01) for the Difficult 

than the Easy Shift Group. The two groups 

began shifts with equal A-state levels; however, 

after shifts, the group which had experienced 

what they judged to be a difficult shift had the 

higher mean score. 

TABLE 3 

Mean A-State Scale raw score for air traffic controllers 

obtained before and after work shifts judged difficult 

and easy. 

Time 

Before Shift 

After Shift 

IV. Discussion. 

Easy Shift 

30.17 

33.10 

Difficult Shift 

29.07 

37.55 

In general, the findings indicate that there is 

a definite relationship between the judged difficulty of shifts and the amount of anxiety reported 

by controllers. Controllers experiencing what 

they considered to be difficult shifts showed a 

greater increase in anxiety during these shifts 

than did controllers who reported a relatively 

easy shift experience. However, it is noteworthy 

that even shifts judged "easy" were anxiety 

arousing to some degree, albeit to a lesser extent 

than "difficult" shifts. Thus, air traffic control 

work, even at its least demanding, is still some-
I 

what anxiety arousing. Whether or not this is a 

characteristic unique 1 to air traffic control work 

and most demanding occupations, or is associated 

with work or work load in general remains to be 

determined. 

With respect to anxiety proneness, it was determined that scores on the measure used in this 

study, the A-Trait Scale of the STAI, were 

predictive of the general A-state level of controllers, but were not predictive of the degree of 

anxiety experienced under the stress of difficult 

shifts. Both relatively high and relatively low 

A-trait controllers showed increases in A-state 

under these conditions, and the increases were 

essentially equal. These findings are thus consistent with research•.g., 1 in which it has been 

shown that A-state responses to "objective" 

threats, such as pain, are not predicted by Atrait level. 

The finding that A-state scores were lower than 

A-trait scores prior to shifts for controllers relatively high in A-trait, while the reverse was true 

for controllers relatively low in A-trait, suggests 

that the impact of undertaking this kind of activity may differ for such persons. On the one 

hand, the relatively low A-trait controller may 

feel some degree o:f arousal and anticipatory 

stress prior to undertaking what can be a demanding job. In contrast, the relatively high 

A-trait controller shows what may be a slight 

decrease in anxiety arousal from general states. 

This suggests the possibility that becoming involved in demanding activities may serve as a 

distraction :for high A-trait persons. In other 

words, such persons may be diverted :from concern over threats to "self-esteem" by involvement 

in demanding activities. This would be consistent 

with the report by Smith3 that student aircraft 

pilots high in A-trait showed lower A-state than 

A-trait scores when undertaking flight instruction 

(even though physiological indicators suggested 

substantial levels o:f arousal), and with the observation by Spielberger5 that patients with high 

A-trait may show reduced A-state by engaging 

in non-esteem threatening tasks. 

Finally, it should be noted that susceptibility 

to anxiety, as measured by the A-Trait Scale, is 

relatively low in the air traffic controller group. 

Even those controllers included in the relatively 

high A-trait group averaged below the 50th percentile :for collegians. Furthermore, while Astate levels were elevated during air traffic control 

work, again the scores were lower than average 

scores for normal college students. These results 

are thus consistent with those previously obtained 

using the STAI with a smaller group of controllers,2 as well as with findings from the use 

of a composite mood adjective checklist. 

REFERENCES 

1. Hodges, W. F., and C. D. Spielberger: The Effects of 

'.rhreat of Shock on Heart Rate for Subjects who 

Differ in Manifest Anxiety and Fear of Shock, 

Psychophysiology, 2 :287-294, 1966. 

2. 1\felton, C. E., Jr., J. M. McKenzie, R. C. Smith, B. D. 

Polis, E. A. Higgins, S. 1\f. Hoffman, ·G. E. Funkhouser, 

and J. T. Saldivar: Physiological, Biochemical, and 

Psyc-hological Responses in Air Traffic Control Personnel: Comparison of the 5-Day and 2-2-1 Shift 

Rotation Patterns. FAA Office of Aviation Medicine 

Report No. AM-73- , 1973. 

3. Smith, R. C.: State-Trait Anxiety Inventory and the 

Assessment of Stress in Private-Pilot Training. Pro-

*U.S.GPO:l992-661-063/400~§ 3 

ceedings of the 80th Annual Convention of the American Psychological Association. 7 :63-64, 1972. 

4. ~mith, R. C., C'. E. Melton, Jr.,' and J. M. McKenzie. 

Affect Adjective Checklist Assessment of Mood Variations in Air Traffic Controllers, Aerospace Medicine, 

42 :1060-1064, 1971. 

5. Spielberger, C. D. : Theory and Research on Anxiety. 

In C. D. Spielberger (Ed.), Anxiety and Behavior, 

Kew York: Academic Press, 1966, pp. 3-20. 

G. Spielberger, C. D., R. L. Gorsuch, and R. E. Lushene: 

The Statc-Tntit An.xiety Inventory Manual, Palo 

Alto, California, Consulting Psychologists Press, 1970.