DOT/FAA/AM-99/22

Office ofAviation Medicine

Washington, D.C. 20591

The Effects ofAge and

Practice on AviationRelevant Concurrent

Task Performance

Ramon M. Milke

James T. Becker

Peter Lambrou

University of Pittsburgh Medical Center

Pittsburgh, Pennsylvania 15213

Howard C. Harris, Jr.

David J. Schroeder

Civil Aeromedical Institute

Federal Aviation Administration

Oklahoma City, Oklahoma 73125

August 1999

Final Report

ZGL C

0,03 ill

5

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

©

U.S. Department

of Transportation

Federal Aviation

Administration

DTIC QUALITY INSPECTED 4 19990916 006
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
Technical Report Documentation Page

1. Report No.

DOT/FAA/AM-98/22

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

4. Title and Subtitle

The Effects ofAge and Practice on Aviation-Relevant Concurrent Task

Performance

5. Report Date

August 1998

6. Performing Organization Code

7. Authors)

Milke, R.M. , Becker, J.T.', Lambrou, P.', Harris, H.C., Jr. ,

and Schroeder, DJ.

8. Performing Organization Report No.

9. Performing Organization Name and Address

Institute for Aviation Medicine and Safety, and Neuropsychology Research

Program Departments of: Psychiatry, Neurology, and Emergency Medicine3

University of Pittsburgh Medical Center, Pittsburgh, PA 15213

4FAA Civil Aeromedical Institute, P.O. Box 25082, Oklahoma City, OK 73125

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency name and Address

Office ofAviation Medicine

Federal Aviation Administration

800 Independence Ave., S.W.

Washington, DC 20591

13. Type of Report and Period Covered

14. Sponsoring Agency Code

15. Supplemental Notes

Work was accomplished under approved task AM-A-94-HRR-126.

16. Abstract

Recent reviews ofthe relationship between aging, cognition, and performance in pilots have emphasized the importance

of considering age effects in aviator skills, particularly perceptual-motor, and memory. One possible conclusion is that

flight experience does not appear to modify this age performance relationship, except in aviator's ability to time-share. A

recent study involving the administration of an aviation-relevant neuropsychological test battery over two days provided

data to examine the extent to which experience moderates the effects of aging on performance. Sixty individuals ranging

in age from 20 to 65 years completed the CogScreen© computerized neuropsychological test battery on five occasions

on two consecutive days. Subjects were divided into three age groups of equal size and within-subject repeated measures

analyses ofvariance (ANOVA) examined the relationship between chronological age and practice on performance. The

performance ofthe subjects in the oldest group was consistendy poorer and slower than that ofthe subjects in the

youngest group for all ofthe measures. There were main effects of practice such that performance after five sessions was

significandy better than that on the first practice session. On none ofthe measures was there a significant age by practice

interaction. In the case of divided attention tasks, significant age by condition (single vs. concurrent) interactions

revealed that concurrent task performance by the elderly was differentially affected, depending on the information

processing demands. These data are consistent with previous reports of experience-based practice effects differentiating

subjects based on age and, by extension, suggesting that age-related factors be considered during systems design and

implementation (including task execution and training for new equipment).

17. Keywords

Aging and Performance, Learning, Multi-Tasking,

CogScreen©, Neuropsychological Tests

18. Distribution Statement

Document is available to the public through the

National Technical Information Service,

Springfield, Virginia 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

16

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ACKNOWLEDGMENTS

The preparation ofthis manuscript was supported in part by funds from the National

Institute ofMental Health to J.T.B., who is the recipient of a Research Scientist Development Award - Level II (K02-MH01077).

in
THE EFFECTS OF AGE AND PRACTICE ON AVIATION-RELEVANT

CONCURRENT TASK PERFORMANCE

INTRODUCTION

As individuals age, there are clear alterations in

their performance ofcognitive tasks. Various models

have been used to describe these changes, including a

reduction in information processing resources

(Salthouse, 1985;Salthouse, 1988), declinesin"fluid"

intelligence (Horn & Cattell, 1966; Salthouse, 1991),

orsignificantslowing ofinformation processing speed

(Birren & Morrison, 1961; Salthouse, 1985). These

age-related changes in cognition are relevant to aviation and are, in part, responsible for the retention of

the Age-60 Rule which prevents pilots from flying

airline transport aircraft after their 60th birthday.

The relationships between aging, cognition, and performance in pilots (military, commercial, and general aviation) have been reviewed extensively byTsang

(1992) and by Hardy and Parasuraman (1997). These

reviews emphasize the importance ofconsidering age

effects in aviator skills, particularly perceptual-motor

and memory. Of special interest is Hardy &

Parasuraman's (Hardy & Parasuraman, 1997) conclusion that flight experience does not appear to

modify this age: performance relationship, except in

aviators' ability to time-share.

This conclusion, regarding flight experience, is

important because it is the ability to divide attention

that appears to maximally differentiate old from

young subjects in a variety ofdomains. For example,

simple digit spans are relatively unaffected by aging,

but backwards digit spans (i.e., repeating the list in

reverse) show age-related decrements in performance

from early adulthood onward presumably because

subjects must simultaneously maintain information

in a phonological store as well as resequence the list.

Simple modifications of relatively straightforward

memory span tasks can produce important changes in

performance, and the greater the processing demands,

the greater the age-related effects (see, for example,

Becker, et al, 1983).

The effect of experience on performance in older

individuals, and aviators in particular, is an importantissue. To what extent does experience, defined as

task-specific practice, alter the affects of age on performance? As part of a recent study (Schroeder,

Harris, Collins, and Nesthus, 1995), subjects were

tested on five separate occasions using an aviationrelevant neuropsychological test battery over two

days. These data provided the opportunity to examine the relationships between aging and the performance ofthese cognitive tasks as a function oflearning

experience. To the extent that such experience moderates the effects of aging on performance, we would

expect a significant interaction between age and time

(i.e., practice). By contrast, failure to find such an

interaction would mean that experience does not

alter this important relationship.

METHODS

Subjects

Sixty subjects (50 men, 10 women), none ofwhom

were licensed pilots, provided data; they were all

participants in a study of the effects of low blood

alcohol levels on test performance (Harris, Schroeder

& Collins, 1995). The data described below represent the first five no alcohol test conditions. Subjects

were divided into three study groups of 20 subjects,

with mean ages of 29.25 (±1.86), 43.6 (±1.69) and

59.25 (±1.89) years.

Procedures

Each subject was tested four times on Day 1, and

a fifth time atthebeginning ofDay 2. Theywere each

administered CogScreen©, a computerized test battery developed by the Advance Resource Development Corporation and Georgetown University (Kay,

1995). CogScreen© was developed in response to a

FAA request for an automated test battery to detect

subtle clinical changes in the cognitive functioning

of pilots. The tests were run on an IBM PC-type

computer, and a light pen was used as the primary

input device for all tests, with the exception of the

tracking task, which involved using the right and left
arrow keys on the computer keyboard. Auditory

feedback occurred during several ofthe tasks. Nine of

the CogScreen© tests were selected for study, and

they were always presented in the same order during

the sessions.

The testsessions were self-paced and usually lasted

30-45 minutes. Subjectwere allowed to ask questions

during and following the first test session on Day 1,

but after that proceeded on their own. Sessions 2-5

did notinclude detailed instructions, were self-paced,

and took approximately 30 minutes. Between each of

the four sessions on Day 1 there was a 15 minute

break during which subjects could read magazines,

watch television, or relax. On Day 2, subjects returned at approximately the same time after eating

lunch approximately 30 minutes prior to their arrival. Testing was conducted as in sessions 2-4.

CogScreen Tasks

BackwardDigitSpan. Lists ofdigits were presented

sequentially on the video screen, with the subject

required to reproduce each sequence in reverse order.

List length increased from three to six digit, with a

total ofeightlists presented. The total number oflists

correctly reproduced in reverse order was recorded

for each subject.

Visual Sequence Comparison. Pairs of strings of

alphanumeric characters, fourto eightitemsin length,

were presented simultaneously on the right and left

halves ofthe screen. The subject indicated "same" or

"different" for each pair of strings, with "same"

meaning, the same characters were in the same positions in both lists. For any pair, the strings could

differ by one or two items; half of the trials were

"SAME" trials and half were "DIFFERENT." The

performance measures included accuracy, mean reaction time, and thruput (number correct per minute).

Symbol Digit Coding. Six pairs of symbols and

digits were displayed near the top of the screen

throughout the test. Farther down the screen a row of

symbols was presented in random order, with blank

spaces below. The task for the subject was to indicate

which digit belonged in each empty cell making

reference to the key atthe top ofthe screen. This task

is analogous to the WAIS-R Symbol-Digit Substitution Task (Wechsler, 1981) and the Symbol-Digit

Modalities Test (Smith, 1968). Immediately after

the Symbol Digit Coding Test, and again after approximately a 30-minute delay, the six symbols

appeared in random order and the subject's task was

to recall the digits that had been paired with each of

the six symbols. For the substitution condition, the

total number of correct responses and the mean

reaction time for each trial, were recorded. For the

recall condition, the total number of correct responses was recorded.

Matching To Sample. A4x4 grid pattern with filled

and empty cells (the "sample") was presented briefly

on the video screen, followed after a short delay by

thatsame pattern along with a slightly different "foil"

pattern. A forced-choice response was required, with

the subject indicating which grid pattern was the

same as the one presented previously. The foils differed from the correct choice by a change in one ofthe

sixteen pattern blocks. Twenty trials were presented

and the performance measures included accuracy,

reaction time, and thruput.

DividedAttention. This task had two parts. For the

first, the Indicator Task, a horizontal bar moved

continuously up or down within a circular display in

the upper half of the screen, changing direction at

unpredictable times. The subject was instructed to

respond when the moving bar passed from the center

region of the circle into the upper or lower regions,

which were delimited by a different color. This response temporarily returned the bar to the center of

the circle. This Indicator Task was performed alone

and concurrentlywith theVisual Sequence Comparison task (see above), which was the second part ofthe

Divided Attention test. These two conditions, i.e.,

Indicator and Visual Sequence, were both performed

alone and concurrently. Thus, there were data for

accuracy (Visual Sequence), Reaction Time (both

tasks), and Premature Responses (Indicator Task) for

both the single and dual administrations.

Shifting Attention. This task was analogous to

several set formation and set shifting tasks, including

the Category Test (Reitan & Wolfson, 1994), Wisconsin Card Sort (Grant & Berg, 1948), and Weigl's

Sorting Task (Weigl, 1927). Four response boxes

were displayed near the bottom of the screen, one

with a colored border, one with an uncolored border,

one with no border but containing a colored arrow

pointing right, and one with no border but with an

uncolored arrow pointing left. Stimuli were displayed in a similar box above this row of response

boxes. There were five conditions, each requiring the

subject to respond according to different rules. The

task began by teaching the subject to respond based

on a particular rule (e.g., Border Color). However,
the rules changed, and the subject was required to

learn to change the response strategy. In the Discovery condition, the taskwas for the subjectto learn and

apply the correct response rule using a trial-and-error

approach. Data from the Discovery condition included accuracy, reaction time, and lost rules (i.e.,

failure to maintain the response set).

Dual Task. There were two tasks, each performed

separately and then again concurrently. The first was

a second-order compensatory tracking task in which

the subjecttapped the right and left arrow keys on the

keyboard to center a vertical bar moving along a

horizontal line. The second task involved the sequential presentation ofsingle digits in random order; the

subject responded with the light pen indicating which

digit had been presented immediately previously.

Thus, if the digits 2-3-1-3-3-2 were presented, the

correct responses would be: NR-2-3-1-3-3. Data

from the tracking task included tracking error and

boundary hits. Data for the Previous-number task

included accuracy, reaction time, and thruput for

both single and concurrent conditions.

RESULTS

The mean results for each subject group on each

measure at each ofthe five test points are presented in

Tables 1 and 2. Also shown in the Tables are the F

ratios for the main effects of group and test trial as

well as the interaction between Age Group and Trial.

The results for accuracy (Table 1) and reaction time

(Table 2) may be summarized as follows. By and

large, there were significant Main Effects of Age

Group and Trial for almost every variable measured.

Thatis, performance ofthe older subjects was poorer

than the younger subjects, and became significantly

better with increasing practice. However, there were

no significantinteractions between Group and Trial,

indicating that the rate of change in performance, as

a function of practice, was similar in all three age

groups ofsubjects.

Because ofthe importance ofthe two time sharing

tasks (i.e., Divided Attention and Dual Task), we

further analyzed these data with regard to change in

performance when the subjects had to perform under

concurrent task conditions relative to single task

conditions. We completed a series of Analysis of

Variance (ANOVA) procedures with the additional

within-subject factor of Condition (Single vs.

Concurrent). These were performed for the Dual

Task and Divided Attention Task measures of reaction time and accuracy. In terms of accuracy on the

Dual Task Previous Number task, there was a significant effect of age (F„ 57)=20.1, p<.001, h

2

= .41), and

test session (E(4228)=37'5> p<-001, h

2

= .40). Furthermore, there was a significant difference in overall

performance on the memory task in the concurrent

condition relative to the single task condition

(F(157)= 138.5, p<.001, h

2

= .71). Of particular interest is the fact that there was a significant interaction

between age group and concurrent condition

(F =3.49, p<.04, h

2

= .11) indicating that the

effect of multi-tasking was greater in the older subjects.

With regard to the accuracy during the tracking

condition of the Dual Task, the results were very

similar. Age (F(257)=11.2, p<.001, h

2

= .28), test

session (F 8)=17.6, p<.001, h

2

= .24), and dual

tasking condition (F(157)=331.0, p<.01, h

2

= .85),

were all significantly associated with performance.

The age by condition interaction was significant

(F,2 57)=6.40, p<.003, h

2

= .18), as was the time by

condition (E(4228)=3.97, p=.004, h

2

= .07) interaction, and the three-way interaction of age, session,

and condition (F(8 228)=2.69, p=.008, h

2

= .09) (See

Figure 1.) Performance by the young subjects improved in the concurrent task condition (E =

7.36, p < .001, h

2

= .28) but that of the middle age

(E,(4,76) 1.45, p = .23, h

2

= .07), and older subjects

(F(4,76) = 1.09, p = .37, h

2

= .05) did not.

Finally, the accuracy data from the Visual Sequence Comparison of the Divided Attention Task

did not reveal a significant effect of age overall

(F(257)= 0.42, p=.65, h

2

= .02). However, test session

(F(4,228)=6.65, p<.001, h

2

= .10) and condition

(F(157)= 83.9,p<.001,h2= .60) did significantly affect

performance. There were no significant interactions

between age and the divided attention condition

(F,2 57)= 1.35, p = 74, h

2

= .03) or between age, session,

and condition (F(8225)=1.08, p=.38, h

2

= .04).

The reaction time data for the two divided attention tasks were transformed prior to analysis in log10

units. A four-way repeated measures ANOVA (task x

dual x session x age) revealed a significant effect ofage

group (F(2 57) = 16.7, p < .001, h

2

= .37), and concurrent condition (F(157) = 365.2, p < .001, h

2

= .87).
Single Task Concurrent Task

60

50

u

2

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•

4

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«•

\

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Trial Trial

Figure 1. Performance on the Tracking component of Dual task. The left graph shows the mean

absolute error by age group over the five learning trials when the task was performed alone.

The right panel presents the same information, but was obtained when the task was performed

concurrently with the Previous Number task.

There was no significant interaction between age

group and concurrent task overall (E(257) = 1.31, p =

28, h

2

= .04). However, the effect of concurrent

condition was significantly greater in Divided Attention, relative to the Dual Task (F(157) = 559, p < .001,

h

2

= .92). Further, older participants were more

affected in the concurrent condition of Divided Attention, relative to the Dual Task (E(257) = 4.41, p =

.02, h

2

= . 13) (See Figures 2 and 3.)

DISCUSSION

These data address several issues of relevance to

aviation and cognitive neuropsychology in the context of aging and human factors. As would be predicted, we found consistent differences across virtually

all measures as a function of age group. That is, the

older subjects (mean age 60 years) performed

consistently poorer when compared with the younger

subjects (mean age 30 years). This finding is not

surprising given the long history ofdata that demonstrate the decreasing efficiency of cognitive operations, especially when measured with attention and

resource demanding tasks (e.g., Birren & Morrison,

1961; Hasher & Zacks, 1988; Morrow & Leirer,

1997; Salthouse, 1991b; Taylor, Yesavage, Morrow,

Dolhert & Poon, 1994).

We also found consistentimprovements in performance across virtually all tasks as a function of

practice. Over the five testsessions, there were marked

increases in accuracy and reductions in reaction time

in all three groups of subjects. However, what is

perhaps more important, is that generally, there were

no significant interactions between age group and

practice. That is, the relative difference between age

groups did not change (i.e., did not get bigger or
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Trial Trial

Figure 2. Reaction time (log10 milliseconds) on the Visual Sequence Comparison Task.

The left hand panel shows the data when the task was performed alone. The right panel

shows performance in the concurrent task condition (i.e., with the Indication Task).

Single Task Concurrent Task

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Figure 3. Reaction time on the Dual Task— Previous Number Task presented alone

(left panel) and with the tracking task (right panel).
smaller) as the subjects had more practice on the

tasks. In some cases, the change in performance by

the oldersubjects only broughtthem to the same level

as that ofthe younger subjects at thefirst test session.

With regard to the tasks that required concurrent

performance, the data overall provided the same

message: Performance was poorer by the older subjects and was poorer in the concurrent performance

conditions relative to when the tasks were performed

alone. Performance of the older subjects suffered

more from the concurrent task requirements and was

consistent with a variety ofother data. In general, the

difference between the single and dual conditions in

the three sets of tasks was not attenuated over the

course ofthe five test sessions. However, in terms of

the tracking performance accuracy ofthe Dual Task,

we also found that this was not true among the

middle age and older subjects. As shown in Figure 1,

these subjects failed to improve tracking performance

during the concurrent condition making the agerelated divided attention effect actually larger. Because tracking skill improved overall (left panel of

Figure) and the Previous Number task showed improved performance with practice under concurrent

conditions, this suggests that the older subjects had

focused their attention on the memory task and made

the tracking task secondary. Thus, while the basic

competence skills necessary to perform the tasks are

relatively unaffected by age, resource allocation is

affected, and only one task can be performed effectively at any given time. This finding could be interpreted in the context ofworking memory (Baddeley,

1986) with an age-related deficit in Central Executive System function at the root of this problem.

Analysis of the reaction time data also revealed

differential sensitivity of the two divided attention

tasks to the effects of age. This finding is consistent

with the literature on executive functioning (See

Baddeley, 1986, for discussion). In the case of the

Dual Task, subjects had to perform a visualtracking

task and a visual memory task. By contrast, the

Divided Attention task involved a visual attention

task and a visual-verbal memory task. By placing

demands separately on visual and verbal modalities,

Divided Attention has less of an executive component (e.g., resource allocation) and, thus, is less

affected by age. By contrast, as Dual Task heavily

loads visual processing, executive demands are greater,

and age has a significantly greater impact.

These data raise interesting questions about the

effects of general aviation-related experience on performance. It is clear that pilots are better able to

manage the effects of age on domain-relevant tasks

(Morrow & Leirer, 1997) than non-pilots, examination of this issue within the aviation community

(e.g., pilots, controllers) is more problematic. Because age is highly correlated with experience (esp.

flight time), it is often difficult to disentangle the

qualitative and quantitative effects that these factors

have on performance. One approach that might be

more useful within the Air Traffic Control (ATC)

environment would be to sample controllers within a

specific age range (e.g., 35-45 years old) stratified by

their age at entry into the ATC system. Alternatively,

one could recruit controllers who enrolled at the

same age and stratify them on their current age.

While neither of these solutions is ideal, together

they could aid significantly in addressing this important issue.

Generally, these findings are important for several

reasons. First, although the performance of older

subjects improves with experience, it may never reach

the same level as that ofyoungersubjects. Thus, when

job task demands and requirements are detailed for

specific operations, they must be created for the

target group as a whole, and not "normed" only on

younger operators. Second, when designing new systems, it would perhaps be imprudent to assume that,

with sufficient experience, older operators would

utilize the systems in the same way, and with the same

efficiency as younger operators; age-related differences in performance, performance style, and cognitive functions, should be considered in designing

new operating systems (Morrow, 1996). Third, the

contrast between the findings from the Divided Attention and Dual Task procedures suggests that system designers should attend to the types oftasks that

must be performed concurrently. Thus, while younger

subjects may be relatively unaffected by task similarities, older subjects are at a disadvantage ifthey must

concurrently perform two or more operations that

involve common information processing demands.

Finally, the introduction of new systems to the

aviation work environment needs to account for the

age-related differences in task acquisition. It seems

clear from these data thatsimple repeated exposure to

a novel task (and novel test environment) does not

maximize performance, although it may optimize

10
operation. Ease of acquisition of a new system needs

to account for these factors. Thus, the fact that new

job candidates (or recent hires) in the aviation field

can learn to operate the new system effectively does

not mean that the same would be true ofindividuals

already in the work force, especially ifthey are over 40

years old. To the extent that the difference between

the old system and the one to be phased in can be

minimized with regard to "look and feel," the effects

of age on performance may be attenuated.

This is one of the first demonstrations of the

negative effect of older age on the acquisition of an

aviation relevant task. The measures ofCogScreen©

have been shown to have significant validity relative

to measures ofin-flight performance (Yakimovitch et

al, 1994). Thus, the failure of the older subjects to

reduce the "cost" of the dual tasking requirement

with practice suggests that this may represent a limit

on their performance ability. However, while age

affects the acquisition ofthese aviation-relevanttasks,

the precise contribution of age itselfis not clear. For

example, the absence of a qualitative measure of

performance, such as cognitive style, precludes an

understanding of whether the older subjects approached the tasks in the same way as the younger

subjects. Nevertheless, these data do emphasize how

age can not only affect performance, but also learning. In keeping with the conclusion of Hardy and

Parasuraman (1997), we did find important agerelated differences in performance on pilot-related

tasks. Future studies must also use aviation-relevant

tasks "that go beyond the typical measure ofcognitive

skill and flight performance" (Hardy & Parasuraman,

1997, pg. 340) to best understand the age-performance relationship in aviation.

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