Technical ~eport Documentation Page 

1. Report No. 2. Government Acces1ion No. 3. Recipient'~ Catalog No. 

FAA-AM-77 -6 

4. Title ond Subtitle 5. Report Date 

PSYCHOPHYSIOLOGICAL EFFECTS OF AGING: DEVELOPING 

A FUNCTIONAL AGE INDEX FOR PILOTS: I. A SURVEY 6. Performing Organization Code 

OF THE PERTINENT LITERATURE 

--- 8. Performing Organization Report No. 

7. Author's) 

Siegfried J. Gerathewohl, Ph.D. -- 9. Performing Organization Name and Addre1s 10. Work Unit No. (TRAIS) 

Office of Aviation Medicine 

Federal Aviation Administration 11. Contract or Grant No. 

800 Independence Avenue, s.w. 

Washington, D.C. 20591 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. ~-~soring Agency Code 

Washington, D.C. 20591 

15. Suppler..entary Notes 

16. Abstract 

This report gives a survey about selected material concerning age and aviationrelated psychophysiological functions. The author analyzes the results obtained 

by many investigators from longitudinal and cross-sectional studies that may be 

useful for the development of a functional age index for pilots. Particular 

emphasis is given to studies on the effect of age differences as measured by 

standardized tests of sensory, perceptual, mental, cognitive and neurophysiological functions and processes, and the quantitative or objective assessment 

of personality traits and structure. A few examples of graphs, tables, curves, 

and mathematically expressed relationships between these parameters and age 

are given. The age-related changes of these variables and their implications 

to possible and actual pilot performance are discussed. 

17. Key Words 18. Oi atribution Statement 

Pilot Aging Document is available to the public 

Functional Age Index through the National Technical In formaPsychophysiological Age Effects tion Service, Springfield, Virginia 

22151 

19. Security Clouif. (of this report) 20. Security Clo11il. (of this pogo) 21. No. of Pages 22. Price 

$3.00 PC 

Unclassified Unclassified .95 MF 

Form DOT F 1700.7 (8-72) Reproduction of completed poge outhori zed 

PSYCHOPHYSIOLOGICAL EFFECTS OF AGING: DEVELOPING 

A FUNCTIONAL AGE INDEX FOR PILOTS: I. 

A SURVEY OF THE PERTINENT LITERATURE 

I. Introduction. 

Human aging is a biological phenomenon with 

profound implications not only for the individual 

but for society and the general public as well. 

Its consequences range from altered structures 

and functions of the component tissues of the 

body to an altered relationship of the oruanism . ~ 

to 1ts physical and social environment. 

In a series of articles dealing with the results 

of the Normative Aging Study conducted by the 

Veterans Administration's out-patient facility in 

Boston, Massachusetts, the contributors stated 

their belief that aging is not a unitary process 

and that at a given chronological age an individual may appear to be older or younger in the 

various areas or aspects of aging. 5 This ambiguity of age as a reliable indicator of gerontological changes has led to the derivation of 

the concept of functional age, which accommodates the fact that persons age at different rates 

along different dimensions. 68 The strategy of 

functional age research is therefore aimed at collecting data on age-related biological, physiological, psychological, and neurological processes and 

functions and at correlating such data with 

chronological age. Functional · age is thus 

thought to be a composite of many age-related 

measures which can be approached through 

statistical analysis. 27 

The ultimate goal for the establishment of 

functional age as a proficiency measure is to 

predict the biological or, in our case, psychophysiological changes based on actua 1 measurements obtained from individuals or groups of 

individuals at various points of their life span. 

If the various functional age points of a person 

were periodically determined, such changes 

could be detected and interpreted as to their 

operational implications. 

The assistance of E. Jean Grimm in preparing this 

manuscript for publication is gratefully acknowledged. 

1 

In order to arrive at an appropriate approach 

to such an effort, it is necessary to collect data 

on age-related functions and to analyze them in 

regard to their general and operational validity. 

This approach seems promising. It may also be 

possible to monitor the aging process in one way 

or another or to accept deviations from an established norm in one or several dimensions as a 

criterion of loss of vitality, proficiency, or of 

incapacitation. Functional age could then become a useful and convenient concept which 

could be applied to problems of variable retirement, for example. 

The purpose of this paper is twofold. First, 

it surveys the material presently available on 

age and aviation-related psychophysiological 

functions. Secondly, this summary of results 

obtained from longitudinal and cross-sectional 

studies concentrates on research data, that have 

yielded quantitative information which can be 

displayed in graphs, curves, and mathematical 

models. A few examples of these are given to 

illustrate the point. They show material obtained by many investigators on the biological, 

physiological, psychological, and neurological 

functions and processes. There is reason to assume that these measurements can he combined 

in certain cases to he representative of the aging 

process within a certain target population. In 

our case, the target population consists of pilots. 

Hence, those measurements and statistics are 

presented here which are associated with or 

thought to contribute to the behavior, performance, and proficiency of aircraft pilots. These 

data are grouped as follows: ( 1) sensory functions, (2) perceptual functions and processes, 

(3) mental and cognitive processes, ( 4) neurophysiological functions, and ( 5) personality 

traits and structure. The age-related changes 

of these variables or parameters and the theoretical and experimental strategies for their investigation and use will be discussed. 
II. Sensory Functions. 

A. Vision. It has long been known that sensory functions deteriorate with increasing age. 

In visual perception, almost all of the functions 

and properties of the eye are affected. One of 

the best-known examples is loss of accommodation or senescent hyperopia (presbyopia); i.e., 

the ability of the eye to focus on objects at varying distances. Precise accommodation curves 

were obtained by many investigators. 21 • 24 They 

show the very early decline of accommodation 

and the steepest slope during the 40- to 50-year 

period. Similar decreases, but not as early and 

drastic, are found in visual acuity and the minimum light threshold of the dark-adapted eye, 

which occur particularly during the 60th decade, 

and in the mean pupil diameter.36 The latter 

one is involved in the process of accommodation. 

The rate of adaptation (i.e., the change in the 

sensitivity threshold as a function of time in the 

dark) is, like pupillary size, contraction latency 

period, binocular fusion time, and color vision, 

only mildly affected by aging. Responses to 

flicker and flicker-fusion frequency also vary 

16 

15 

14 

13 

12 

II 

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~ 8 

2 7 

0 

6 

5 

4 

3 

2 

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10 20 30 40 

with age and show a sharp decline in older 

people and so does the extent or size of the visual 

field. 62 While up to age 45 depth perception 

(stereopsis) changes very little, it declines at a 

much faster rate thereafter.' There are some 

indications that the mechanical effects of aging 

in the anterior segment of the eye occur earlier 

than those affected by metabolic changes in the 

retina. Both static and dynamic visual acuity 

decrease after age 54, probably due to changes 

in efficiency of the visual apparatus or its functions.35 

An example of the effects of age on vision 

showing the decrease in the amplitude of accommodation is given in Figure 1. 

B. Hearing. Very accurate hearing curves 

have been plotted over the years. 8 • 82 There is 

an age-related diminishing of the general auditory sensitivity (total and relative) and a hearing 

loss especially for the higher frequencies (above 

2,000 Hz), but the very low frequencies (below 

100) are also affected. It appears that most 

individuals above age 40 show some loss of high 

tone perception. Recent research in this area 

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AGE IN YEARS 

FIGURE 1.-Age changes in thP amplitude of visual accommodation based on Duane's curvt>s of norms and accommodation. (Curve based on Figure 26 in Crouch, E. L.: '!'he Helation Bt>twePn Illumination and Vision, ILLUMINATION ENGINEERING, 40:747-784, 1945.) 

2 
concerns the associated processing abilities, since 

the aging auditory system has decreased capacities in integrating and understanding distorted 

messages even in persons who have relatively 

normal audiometry. In a delayed speech feedhack experiment, it was found that the younger 

subjects were less affected by the delay than the 

older ones, but the differences were minorY 

Similar results were obtained in a two-click discrimination task. The performance of persons 

of different age groups on a dichotic listening 

task showed that recall declined with increasing 

age. The deficit was predominant for the leftear material." 0 In an attempt to develop an 

auditory functional age formula, 16 different 

auditory variables were used in a multiple regression analysis.6 The 10 highest ranking correlations ranged from .40 to .25, the two highest 

being air conduction at 8,000 Hz and speech reception threshold. All correlations obtained in 

this experiment clearly confirm the well-known 

hearing decrement observed in the various age 

groups. An experiment on the effect of age on 

the perception of vibration showed that the 

threshold of vibration sensation rose with age. 97 

The logarithms of the threshold values were directly proportional to age, and the standard 

deviations increased proportionally. There also 

is a correlation between chronological age and 

vmce characteristics. A "classical" hearing 

acuity curve as affected by age is shown in 

Figure 2. 

III. Perceptual Processes. 

A. Data Acquisition. Age-related changes in 

perception are not necessarily caused by, or even 

related to, changes in the sensory functions. 

"While sensory stimuli may include elements of 

stimulus integration, interpretation, and judgment, which contribute to the detectability, processing, and application of the sensory input, the 

stimulus or data handling process is very complex and can proceed independently of the 

original input. An example of this process is 

the visual illusion, which is characterized by the 

false interpretation of a real sensory image or 

impression. A different but related factor in 

perception is time; e.g., information processing 

time, response time, and the timing of sensory 

input. Older persons need longer exposure time 

for form identification. In experiments usmg 

3 

the Mackworth clock test, for instance, older 

subjects were found to be as "vigilant" as the 

younger ones, hut their performance declined 

significantly after 45 minutes. This deficit in 

visual performance of the elderly was particularly obvious when stimuli of short duration (1 

sec or less) were applied. 99 

During a "paced inspection task," sequences of 

letters and digits were presented to subjects who 

had to monitor the occurrence of consecutive 

letters or digits. The age-related impairment of 

performance was most pronounced after age 60. 26 

It was suggested that this type of performance 

can be improved if the information is simultaneously presented visually and auditorily instead of only visually. Such kind of presentation 

helped the older people more, because the agerelated reduction in information processing capacity is compensated by relegating the auditory 

sequence to a kind of secondary task. Ry splitting the total sequential process into two parts, 

performance in the primary visual channel can 

be maintained at a higher level. 

In view of the fact that perceptions are usually 

transformed into cognition and action and that 

they are also closely related to neurological, 

psychomotor, and central mechanisms, complex 

perceptual processes have been likened to such 

concepts as information and communication 

theory. Timing appears to be an important 

factor involved in these mechanisms, although 

experience and strategy may play a certain role 

in communicating and information processing. 

Since the observed age difference between young 

and old persons are neither consistent nor very 

large, it is hypothesized that specialized training 

and extended practice, both typical for older 

people, may help to keep their performance 

deficit at a minimum. 

B. Information Processing and Channel Capacity. Information theory deals with the 

amount of uncertainty involved in any communication process. It is based on the assumption 

that the human brain is a rather noisy communication channel and that signal detection proceeds statistically in that the cognitive mechanisms always test hypotheses, so to speak, in 

order to discriminate between noise and signal. 

It is clear that the time available for signal 

sampling and processing is very important for 

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FIGURE 2.-Age changes in the acuity of hearing. Xote that: (a) points deduced from small frequencies near the 

terminals of the range are marked by clear circles, and a heaYy circle is shown replacing several such points; 

(b) the standard deviation a of the dependent yariable is indicated so that the extent of the total variation 

of one character with the other will he readily apparent. (Reproduced with permission from Diagram I in 

Koga, Y., and G. J\f. Morant: On the Degrt>e of Association Between Reaction Times in the Case of Difft>rent 

Senses, BIOMETRICA, 15 :346-372, 1923.) 

the outcome of this type of signal detection. 

Experiments aimed to throw some light on the 

timing characteristics of this process furnished 

some interesting results about the task load. 

Rapid judgments and decisions had to be made 

in the interpretation of a large variety of signals. 

vVhile there was no obvious slowing of the subject's response time to the stimuli, subjects over 

40 years of age were relatively more susceptible 

to information overload than the younger ones, 

particularly when the task involved the presence 

of temporally contiguous (or masking) signals.100 

4 

Recently, investigations of the effects of backward monoptic and dichophic visual noise masking also showed that older subjects were more 

affected by visual distortions than younger subjects.20· 5 ' The authors conclude that this effect 

seems to be, at least partly, attributable to age 

changes in the central perceptual mechanisms 

involved in the processing of signals. Backward 

masking studies of various kinds seem to hold 

considerable promise for the assessment of the 

peripheral and central components of age changes 

in visual processing. 
C. Reaction Time. Simple reaction time (RT) 

(i.e., making a response to one discrete stimulus) 

becomes definitely slower with increasing age. 

Reaction time curves and mathematical expressions of this function have been known for more 

than 50 years. 58 Relative to other functions, reaction time appears to mature early, reaching its 

minimum at about age 20. It seems that even in 

this simple stimulus-response mechanism, central 

processes play an important part. Choice reaction times are always longer than simple RT at 

all ages. When choices between several possible 

responses are required, an extra time delay has 

been measured with older suhjects. 22 In experiments including complex reaction tasks, the older 

test subjects were significantly slower in complicated test situations than the younger ones, particularly when the tests involved reversing or 

changing the previously learned stimulus/ 

response relationship of the signa1s. 91 There 

were no significant differences between the 

younger ( 20-28 years) and the older ( 48-62 

years) age groups in motorically responding to 

the various tasks, hut the information processing 

rates were different: 13.7 and 10.6 bits/sec for 

younger and older subjects, respectively. 50 \Vhen 

test subjects had to make one-syllable responses 

in order to form two-syllable words, the choice 

RT's were found to he lower in older than in 

younger subjects. The difference between simple 

and complex reaction times was greater for the 

older than for the younger onesY2 There were 

some speculations that the older subjects were 

more affected by the length of the alerting period 

(i.e., the time period before the stimuli were 

presented), but it was found that the older persons did not benefit from extending the alerting 

periods or other advance infonnation. Age 

changes in choice reaction tasks also manifested 

themselves in increases in errors and increased 

variability of RT. 23 Long-term nrhal habits, 

as measured by these word-association tests, 

however, facilitated the performance of the older 

subjects on some tasks. This shows that they 

were more inclined to think in realistic terms 

than the younger subjects who were more oriented 

toward abstract thinking. so 

In an experiment involving visual perception, 

the time needed to discriminate and then react 

improved from a 15-16 year group, reached its 

peak at 30-35 years, and then declined steadily 

from 55-60 years to the oldest group (70 and 

5 

over) ,

90 There is also evidence that the older 

individuals responded relatively slower to repetitive stimulus patterns than to changing stimulus 

patterns. Their longer reaction time reflects impaired efficiency in initiating motor responses 

rather than in discriminating between the visual 

stimuli.114 

By measuring promptness of response with a 

word-identification test, it was found that the 

older subjects gave fewer responses. This was 

probably due to the slowing of the perceptual 

processes involved." 9 It now seems that with 

increasing age the processing of the perceived 

information and the monitoring of ongoing responses cease to be integrated by the central 

nervous system as efficiently as during the 

younger years and that the two steps may have 

to he undertaken sequentially rather than simultaneously.77 This is in agreement with our earlier 

statements. In a more recent study involving 

stimulus repetition in a two-choice experiment, 

it was found that response latencies increased 

with age and that the older individuals' longer 

response times reflect impaired psychomotor 

rather than decision-making efficiency11•

5 Since 

previous results suggested that motor factors 

were not adversely affected during such tasks, 

the ambiguity of the results still exists. 96 Two 

examples of reaction time curves as a function 

of age are given in Figure 3. 

D. Psychomotor Performance. Sensory, perceptual, decision, and motor processes are involved in psychomotor performance. All are 

more or less affected by aging. It was found 

in early experiments that a more complex motor 

response can in some 'vay enable compensation 

of an otherwise slow RT. Experiments in which 

complex sensorimotor coordination was required 

have shown pronounced deficits with age. In 

particular, slowing of speed was observed during 

writing, finger tapping, and tracking. 67 • 117• 118 

An experiment to determine the fing·er-tapping 

rate by alternating between two targets showed 

that the rate improved in accuracy and speed 

from the 20th to the 30th year and thereafter 

declined with age. 16 No significant age differences were found within the range of 17-41 years 

of age on the USAF Rotary Pursuit Test. 18 In 

another experiment, the test subjects had to respond to either tones given monaurally in each 

ear or to voice commands presented binaurally 
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Age in Years 

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FIGURE 3.-Age changes in the speed of reaction time. 

Graph A-digital and foot reactions compart>d. Graph 

B-four types of hand and finger reactions compared. 

(Adapted from Figurt>s 4.2 and 4.3 in Dennis, W.: 

Age and Behavior-A Survey of tlw Literature. USAF 

School of Aviation l\ledicine, Randolph Field, Texas, 

P. No. 21-0202-0005, 1953. Original figures from 

l\files, W. R. : Measures of Certain Abilities Throughout the Life Span, PROCEEDINGS OF THJ<J XATIOXAL ACADEMY OF SCIEXCES OF THg 

UNITED STA'l'ES OF Al\IERICA, 17:627-633, 1931.) 

in head phones. The younger subjects responded 

significantly faster than the older ones to both 

types of stimuli. Moreover, the difference in response time between the directionally presented 

tone cues and the voice cues were significantly 

greater for the older people.92 

When the effect of task complexity and stimulus duration on perceptual motor performance 

was studied in two disparate age groups, the 

older subjects reacted 30 percent slower and 

moved 76 percent slower than younger ones. 

Both perception time and movement time were 

6 

slower in complex tasks than during a simple 

performance test. Young subjects moved more 

rapidly with the 0.110-second stimulus, while 

older subjects moved relatively faster when a 

2.0-second stimulus was presented.112 In general, 

the perceptual motor performance of the older 

subjects was found to be substantially worse than 

that of the younger ones. This difference was 

due particularly to the longer time required for 

discrimination of the stimulus and the decisionmaking process.64 The older subjects also responded more slowly when advanced information 

signals were presented. These data suggest that 

older people are at a considerable disadvantage 

when coping with new test situations and acquiring new skills, since they must learn to predict 

further ahead in time than their juniors in order 

to be efficient. The better performance of the 

elderly in certain laboratory tests was due more 

to their increased eagerness to perform well than 

to their perceptual motor capabilities. This may 

not be of help, however, in practical situations 

where the ability to anticipate is essential. Functionally, the inferior performance of the elderly 

is interpreted as reflecting a slowing of the general speed factor, which underlines most perceptual and neural processesY· 76 

It is commonly found in a wide variety of 

performances that individual differences increase 

with age. 111 • 112 1Vhereas motor coordination 

seems less affected by the aging process, performance decrement is most apparent in functions 

which require visual motor responses or when 

speed is of particular importance. A certain 

amount of the decrement in psychomotor performances includes the mental or thinking part 

of the processes involved. This can be found 

even in experimental results which show a wide 

range of individual differencesY 

The effects of age on the 12 ability tests of the 

General Aptitude Test Battery (GATB) 'vere 

examined as part of the Normative Aging Study. 

All scores showed highly significant declines 

with age, hut the magnitudes of the decrements 

differed greatly. 69 Most affected by age was the 

psychomotor test requiring the disassembling of 

a simple mechanical gadget. Performance on 

the three ability tasks, namely Dissemble, Tool 

Matching, and Turn, which required the manipulation of small objects, accounted for about 

25 percent of the variability in chronological 

age.4o 
There is also some evidence that there is more 

than one speed factor involved in psychomotor 

performance and that the speeds of perceptual, 

motor, and complex cognitive functioning are 

relatively independent of one another. In a 

complex experiment performed to throw some 

light on the interaction of these functions, it was 

found that the older individuals performed more 

poorly than on certain tests requiring speed. 

Again, information processing was most affected 

and declined with age.116 Experiments confirmed 

a similar decline of vigilance as part of a psychomotor assessment. Older test subjects' performance decreased more at the fastest speed used 

than did that of the younger ones.111 In another 

study measuring the response speed deficits and 

intellectual performance in the elderly, it was 

suggested that a major proportion of intellectual 

decline in old age reflects performance rather 

than competence deficits. 52 It was also hypothesized that older subjects make best use of their 

capacities through unconscious (or conscious) 

improvement of their performance (i.e., they 

tend to adopt the optimum strategy to solve a 

problem more readily than do the younger ones). 

However, an experiment on risk taking showed 

that the older subjects' performance did not improve through unconscious optimization when 

compared to that of the younger group.84 

IV. Mental Processes. 

A. Learning. The ability to retain new information in a readily accessible state deteriorates 

with increasing age. This decline has been attributed to an impairment of the mechanisms 

active either in the acquisition or the storage of 

new information, and there is evidence to support 

both theories. It seems quite probable that efficiency declines in all steps involved, namely 

acquisition, storage, recognition, and recall. A 

series of experiments in paired-associate learning 

has demonstrated that the capacity to acquire 

new verbal information deteriorates with age 

faster than the other processes involved.105 Comparisons between very old persons and those in 

the prime of their lives showed, of course, the 

former at a disadvantage in tests of virtually 

any cognitive function. This encompasses such 

specialized processes as discrimination learning 

consisting of reversal, intradimensional, and 

extradimensional tasks. It was found in an experiment on discrimination learning and transfer 

7 

of training that the younger subjects made 

significantly fewer errors than did the older 

trainees. 65 This seems to indicate a greater susceptibility to negative situational transfer or 

mediationally deficient functioning with increasmg age. 

Performance scores and learning curves obtained with the U.S. Air Force DiscriminationReaction Time ~\_pparatus declined steadily after 

about 25 years of age. As expected from the 

literature, the classical nonmonotonic age learning function "·as found in these experiments 

(i.e., that capacity for learning decreases with 

age) .sa 

The reason for the reduced ability of the 

elderly to properly learn, recall, and process any 

information may he due either to the diminishing 

capacity of the aging brain to form structured 

traces of the incoming message or to an increase 

in neural noise as previously hypothesized. 23 An 

attempt to improve the learning ability of the 

elderly by the administration of a drug, 

propranolol, as an autonomic nervous system 

stimulant, yielded promising results. 31 

B. Jvl emory. Short-term memory generally 

shows a relatively slow decline after maturity 

and a marked decrease during the sixties and 

seventies, particularly in tests using unfamiliar 

material.121 •

122 'Vhile there is experimental evidence that retrieval time becomes slower, a comparison with perceptual and response factors 

indicated that memory searching time is less age 

related. 3 • 56 In order to find an answer to the 

storage versus retrieval deficit question, series of 

experiments were conducted using several span 

and recognition tests. 'Vhen simple and complex 

visual patterns were applied, age-related decrements in short-term memory were determined. 

They interacted in a very complex manner with 

other variables, such as stimulus condition (paced 

or self-paced), complexity, exposure time, etc. 

The analysis of the encoding process did not 

suggest any reliable relationship between shortterm memory and encoding strategy or retrieval 

phase but did show age-related deficits at the 

recognition stage. 2 On the other hand, older 

persons showed no deficit in immediate memory 

span and retrieval from old storage but highly 

significant impairment in learning long digital 

sequences and verbal items. This was interpreted 

as storage disorders instead of a retrieval deficit. 29 
It has been suggested that methodological 

problems may account for some of the differences 

in results obtained by age-related memory 

studies." Possibly, repeated testing and practice 

could improve the memory in old persons, but 

experimental proof of this theory was not obtained. Although there were age-related deficits 

with two types of test material used, the sense 

modality effects (visual vs. aural) were similar 

for all age levels.108 Although no differential 

output or input interference due to age was found 

for items assumed to be recalled from long-term 

memory, an overall deficit was observed on these 

long-term items.94 Hence, susceptibility to interference appears to be closely associated with the 

relatively poorer performance of the older subjects in both short-term and long-term memory 

tasksY• 106 

Similar results were recently obtained in experiments on semantic (verbal) memory. The 

age effects were different for recall and recognition in that the older group responded more 

slowly on the recognition but not on the recall 

part of the task. The response times of the 

older subjects were less affected by the dominance 

of the to-be-retrieved information than were 

those of the younger ones. These results were 

interpreted as suggesting that subjects in the 

higher age brackets may have retrieved information just as fast as the youngsters but that they 

require longer times to decide upon the response. 34 

Both young and old subjects performed more 

poorly as the stimulus arrangement became more 

complex, and there is evidence that the decrement 

was more pronounced with the older group. 51 

Practice or repeated testing may help somewhat 

under these conditions, but it did not seem to 

aid the elderly more than the young. 109 Perhaps 

differences in interest and motivation can influence what will or will not be recalledY An 

example of the age-related recall function obtained in experiments using nine-digit numbers 

is shown in Figure 4. 

C. Problem Solving and Performance. Several studies reported during the past 15 years 

deal with the effects of age on intellectual and 

cognitive functions. Their results-even those 

obtained by the same experimenters-are sometimes ambiguous.49 Using the Wechsler-Bellevue 

and the Wechsler Adult Intelligence Scale, decline and no-decline of test scores with age were 

found in different populations.121 The effect of 

8 

70 

60 

50 

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0 

(.) 40 

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~ ... 30 ()) 

0.. 

20 

10 

.... Auditory .... ... .... , 

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20 30 

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40 

Years 

• 

70 

FIGURE 4.-l\lean complPtP rPcall pPrformance with ninPdigit numb!'l's prt>sPntPd am·all~' and visually to fivP 

age groups. (RPproduePd with permission from 

Figure 7 of Talland, G. A.: Human Aging and Behavior, Xew York, Academic Prt>ss, 1968, 322 pp.) 

aging as measured by the General Aptitude Test 

Battery (GATB) showed declining scores on all 

12 subtests. Most affected was the psychomotor 

test, while Arithmetic Reasoning and Vocabulary 

were least affected."8 Age-related performance 

decrement in a paced inspection task was most 

marked after age 60. 33 However, there seems to 

be enough evidence to conclude that some intelligence test scores do not decline before age 65. 

This is especially the case with measures of 

verbal abilities; in contrast, test and performance scores which depend on sensory and motor 

processes declined with age (see Figure 5). 39 As 

previously reported, older subjects tended to 

slow disproportionately in performing speeded 

tasks in a problem-solving reaction-type test. 

The older subjects also made more errors, and 

the correlation between slowness and inaccuracy 

increased with age. Elderly persons are not 

necessarily more careful; or, if so, this cautiousness does not effectively compensate for error 

proneness. The age effects in error proneness 

and the slowing of cognitive functions indicate 

an increased difficulty of the aged in maintaining 

effective control of cognitive activity.H 
A 

60 

50 

40 

30 

B 

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60 

50 

40 

30 

20 I 

10 r 

10 

10 

~=: 

20 30 

20 30 

··. ·". ~-, 2 5°/o ',, ·~· 

GENERAL POPULATION 

MESSRS_ LTD--

GPO ENGINEfRS--

40 50 

AGE IN YEARS 

60 

GENERAL POPULATION 

MESSRS_ LTD 

70 

GPO ENGINEERS--

40 50 60 70 

AGE IN YEARS 

25% 

FIGURE 5.-Performance as a function of age and occupational status. Graph A-performance on Progressive Matrices, a nonverbal intelligence test. Graph 

B-performance on the Mill Hill Vocabulary Test. 

(Reproduced with permission from Figures 8-3A and 

8-3B in Birren, J. E.: The Psychology of Aging, 

Englewood Cliff, New Jersey, Prentice-Hall, Inc., 1964, 

300 pp. Adapted from Graphs I and II in lfoulds, 

G. A., and .J. C. Raven: Normal ChangPs in the Mental 

Abilities of Adults as Age Advances, .TOURJ\"AL OF 

MENTAL SCIEJ\"CE, 94:123-142, 1948.) 

A great deal o:f research into the changes 

which occur in skilled performance with advancing age suggests that the processes most crucially 

affected are those central ones which mediate the 

translation o:f perception into action. This can 

be interpreted as a deterioration o:f the operator's 

capacity to transmit information :from display 

to control. 50 I:£ events requiring :fast action by 

an operator occur at random, they impose a continuous risk of momentary "overloading" of 

channel capacity. Another disadvantage :for 

older people who operate mechanized equipment 

is that the direct relationship between \Vhat is 

seen and what is done is lost. It has been shown 

9 

that indirect display-control relationships are 

disproportionately more difficult to handle :for 

older people than :for younger ones. 

In an analysis o:f intellectual performance of 

older persons, tests measuring verbal achievement 

reflected little or no decline.32 • 34 By using a 

superior synonym test and a sophisticated qualitative scoring technique, however, age differences 

were :found with the fine nuances of word definitions: The performance of the 70-year group was 

:far below that o:f the 20- to 60-year group. 12 As 

to the testing o:f nonverbal intelligence, it was 

found that there were little differences in performance among young, middle-aged, and old 

individuals. It was suggested that intelligent 

old subjects may retain an ability to learn to a 

certain degree from immediate experience which 

enables them to compete successfully with 

younger ones.120• 121 

Extensive studies were recently conducted by 

several investigators to measure age-related differences in mental abilities and skills using a 

variety of psychological test batteries. 38• 42• 73 

Performance on practically all of these tests 

showed decreasing efficiency with age, but the 

degree of decline of test scores varied remarkably. Several o:f the mental :functions, such as 

arithmetic reasoning, vocabulary, and verbal 

skill, did not decline as much as other :functions. 

The major age-related differences o:f these functions were observed between subjects in their 

sixties or seventies and the younger ones. The 

largest decrements were measured in tasks which 

were unfamiliar to the subjects. 43 A review of 

the literature on age-related Piagetian cognitive 

:functions (logical operations, animism, moral 

development, egocentrism) indicated wide individual differences in adulthood cognitive performance, showing continued cognitive development for at least some middle-aged subjects on 

certain tests. Generally, lower levels of cognitive 

functioning were noted :for elderly subjects as 

compared to the adult groups. 74 

Data obtained by a study o:f age differences in 

intelligence performance support the hypothesis 

that part o:f the often-reported age effects in 

components of intelligence is not indicative o:f a 

loss in task-specific abilities but n:tay reflect, at 

least partly, the effect o:f nonintellective factors 

associated with such variables as pretest experience and subtest position!" Indications of 
cohort-related differences were also found in agerelated intelligence studies.86 Figure 6 shows 

cohort differences on some primary mental abilities and on measures from the test of individual 

rigidity. 

The results of a 35-year followup study of 

intellectual functioning showed a slight insignificant rise in vocabulary level but a decrease in all 

groups of mental efficiency scores and indexes for 

the 60- to 74-year-old subjects. 47 When the 

scores of each older individual were compared 

A 

with his scores obtained 35 years earlier, all differences from the higher indexes were significant 

at the 0.01 level or beyond. However, variation 

in the amount of decline is pronounced among 

older persons and many, even though they may 

have lost their former efficiency, were still on 

par in some areas with the average young person. 

Table 1A shows the mean scores, standard deviations, differences, and significance of the differences of the scores obtained in the 1930's and 

1970's. Table 1B shows the mean total efficiency 

VERBAL 

58 

MEANING 

SPACE REASONING NUMBER WORD 

FLUENCY 

44 

42 

40 

B 

. 

q 

' 'o 

58 

56 

INTELLECTUAL 

ABILITY 

54 0\ I 

52 I 

~ 50 ~ C) \ 

~ 48 I 

v, b_'O 

I 46 1 1-... I 

44 

42 

40 

I 

I 

I 

I 

\ 

Q. 'q 

' 'o I 

I 

I 

q 

' 

~ I 

I 

' 0 

' I 

\ 

0 

'31 I I' '17 I' '03 II '89 

'24 '10 '96 

EDUCATIONAL 

APTITUDE 

·3; h'7h)JI ·89 

'24 '10 '96 

. 

I 

I 

o-o 

'31 I II '17 I' '03 I' '89 

'24 '10 '96 

Bl RTHYEAR 

MOT0R·COGNITIVE 

RIGIDITY 

'24 10 '96 

Bl RTHYEAR 

' I 

0, 

'o 

t(L I 

~~ I 

I 

I 

I 

I 

I 

o_ 

'0 

...,. Partic1pants 

I I ~-0 ~onpar~ICIP,Onl{ I 

'31 I '171 ·o3l '89 '31 h71 ·ool '89 

'24 '10 '96 '24 '10 '96 

PERSONALITY 

PERCEPTUAL 

RIGIDITY 

' 'o 

\ 

0-0 I 

\ 

I 

\ 

0 

I 

\ 

\ 

I 

o, 

I 

\ 

0 

PSYCHOMOTOR 

SPEED 

o,o 

I 

I 

b, 

' q 

' ' 0 

' I 

I 

6.'b 

-Participants 

o- -o lvonparticippnts 

,:-:-'3\-+1 ,:-':-1'7+1 ·o-'- 13+:-1 '81- 19 

'24 '10 '96 

FIGURE 6.-Cohort-related differences on the primary mental abilities (Graph A) and on 

both global indices of mental ability and measu.res of behavioral rigidity (Graph B). 

(Reproduced with permission from Figures 1 and 2 in Schaie, K. W., G. V. Lahouvie, 

and T. J. Barrett: Selective Attrition Effects in a Fourteen-YPar Stud~- of Adult 

Intelligency, JOURNAL OF GERONTOLOGY, 28:328-334, 1973.) 

10 
TABLE l. Data on Intellectual Functioning From a 35-Year Followup Study by Gilbert 47 

A. Averaee Earlz and Late Efficiencz Scores on the Grou2s of Tests 

Total Easy-Old Initial Motor Easy 

No. Vocabularz Score Material Re[!etitions Learning Retention Reactions Continuous 

1930's 14 

Mean 18.71 18.19 18.24 16.97 17.21 18.84 20.05 17.68 

SD 1.87 1.12 1. 44 2.40 1. 64 2.58 1. 77 1.48 

1970's 14 

Mean 19.71 15. 15 17.39 15.95 13. 18 13.22 16. 10 14.78 

SD .80 2.07 1. 68 2.17 3.59 3.72 3. 11 2.04 

Diff. +1.00 -3.04 -0.85 -1.02 -4.03 -5.62 -3.95 -2.90 

SED .56 .65 . 61 .90 1.12 1. 26 .99 .70 

t 1. 77 4. 12** 1. 38 1. 14 3.60** 4.48** 3.98** 4.08** 

B. Efficiencz Indices of the Two Grou2s 

Mean Easy-Old 

No. Total E. I. Material Re2etitions 

1930's 14 +1.00 +1. 08 -0.20 

1970's 14 -2.82 -0.21 -1.94 

MD -3.82 -1.29 -1.74 

SD 1. 71 1. 79 1. 82 

SEDM 0.45 0.47 0.48 

t D 8.48*** 2.74* 3.62** 

c. Efficiencz Indices Based 

Mean Easy-Old 

No. Total E. I. Material Re2eti tions 

1930's 8 +1.61 +1 .15 -0.69 

1970's 8 -1.46 +0.50 -0.84 

MD 3.07 0.65 0. 15 

SDD 0.85 0.97 1. 45 

SE MD 0.30 0.34 0.51 

t 10.23*** 1 .88 0.29 

* E. < .02 ** E. < . 01 ***E. < .001 

indices o£ the two groups, their efficiency indices 

on the six separate groups o£ tests, the differences 

between the early and late indices, and the significance o£ these differences. Finally, Table lC 

shows the average efficiency indices o£ eight test 

subjects based on the vocabulary scores they obtained during their first test in the 1930's. Generally, it was noted that adult persons perform 

quite well on such tests, whereas many old persons show an apparent regression in task mastery, 

performing at levels similar to those o£ young 

children.10 

In summary, it appears that older people 

usually perform more poorly on tasks requiring 

sensorimotor, mental, and cognitive performance, 

and problem solving (see Figure 7). These 

deficits are due not only to the slowing process 

o£ the £unctions involved but also to such factors 

as lack o£ practice, loss o£ touch with current 

problems, and unawareness o£ present needs and 

11 

Initial Motor Easy 

Learning Retention Reactions Continuous 

+0.1.6 +1. 34 +2.39 +0.29 

-4.50 -4.95 -2.17 -3.49 

-4.66 -6.29 -4.56 -3.78 

3.69 2.55 2.27 2.01 

0.98 0.68 0.61 0.54 

4.75*** 9.25*** 7.48*** 7.00*** 

on Earll Vocabularl Levels 

Initial Motor Easy 

Learning Retention Reactions Continuous 

+0.85 +1.47 +2.35 +0.94 

-2.71 -3.01 -1.35 -1.94 

3.56 4.~8 3.70 2.tltl 

2.59 1. 86 2.58 1.60 

0.92 0.65 0.91 0.56 

3.87** 6.89** 4.06*** 5.14*** 

requirements. The deficit is compounded slowly· 

£rom the midfi£ties on, followed by relatively 

pronounced declines in cognitive performance in 

the sixties and seventies and thereafter. The 

interaction o£ these variables complicates the interpretation o£ the deficit as well as its implication to practical situations. It also appears that 

maturity and experience can hardly compensate 

£or the deficit in some o£ the £unctions which are 

critical £or sustained performance and proficiency. 

V. Neurophysiological Functions. 

A. Biological Considerations. Experiments 

have shown that cells, particularly the highly 

differentiated ones in many critical organs such 

as the human brain, die in the course o£ aging. 1 

This seems to be indicative of the physiogenetic 

basis £or the age changes in the various body 

systems and functions, which affect the daily be-
130 

120 

~ ~ 

~ 

'-.l 110 V) 

~ 

~ 

~ 

h.. 100 ~ 

Q.. 

~ 

~ 90 

~ 

~ 

~ 80 ~ 

~ 

~ 

70 

NUMERICAL 

• • 

3 X-K 

4 o--o 

5-7 .,__.... 

SPATIAL FINGER 

DEXTERITY 

30 40 50 60 30 40 50 60 30 40 50 60 

MID-POINTS OF AGE GROUPS 

FIGURE 7.-Effects of age on three GATB aptitudes. The Warner Level indicates the 

socio-economic status of the test subjects. (Reproduced with permission from 

Figure 1 in Fozard, J. L., and G. D. Carr, Jr.: Age Differences and Psychological 

Estimates of Abilities and Skills, I::\DUSTRIAL GERO::\'TOLOGY, 13 :75-96, 1972.) 

havior pattern of the individual. Many observations on both healthy and sick or diseased persons 

have indicated that there is a decrease in cerebra] 

metabolic rates or oxygen consumption with age. 61 

Although there was no significant age effect related to blood flow in the brain, there was a 

considerable and statistically significant decrease 

in cerebral glucose utilization in otherwise 

healthy elderly subjects, resulting in a somewhat 

reduced mental capacity. In some instances, 

there was evidence of loss of cerebral tissue. 25 

The decrease in skeletal-muscle mass with increasing age explains to a large extent the decrement of physical and muscular efficiency (see 

12 

Figure 8). The cardiovascular reflexes, which 

adapt the blood circulation to muscular and 

heavy aerobic work, also seem to be affected. 

There is indication that decreased sex hormone 

production and reduction of thyroid hormone 

may be involved in the physical deterioration of 

older persons. 93 \Vhile one cannot imply that 

the decrement in the total number of cells and 

the deficiency of oxygen metabolism within the 

cells are the only factors in aging, both variables 

are most intimately related to the age factor. 

Multiple causality is undoubtedly involved in 

such a complex process as aging. 
•-------• M~chanical Efficienc4 

Endurance- Heav4 Work 

•---• Maximum Oz Intake 

,--""" ... ,.- ... ~ ,____ ------ ... ... _ OIL , ---... ,- - 0. 

100 

,, ...... .,, ,, ... ~ 

---, ...... o, -....... Dill ............ 

tJ) 

~ ' . 90 0 

~ 

'\...\ ........_ bj /Jso 

1- .......... /] 

u 

~ 80 

0 

~ 

t: 70 ~ 

0 

1... 

~ 

~ 60 

50 

........... 

' ' 

50 

' ' ' ' '· 

35 

40 Aqe -Years FIGURE 8.-Effects of age on mechanical efficiency in moderate aerobic work (Robinson, 

1938), the maximum O, intake in aerobic work (Dill, 1942 ; Robinson, 1938), and 

endurance in heavy aerobic work (Dawson and Hellebrandt, 1945) expressed in percent of peak performance between 30 and 40 years. (Reproduced with permission 

from Figure 5 in Simonson, IlJ.: Functional Capacities in Older Individuals, JOURNAL OF GERONTOLOGY, 13:18-26, Supplement No. 2, 1958.) 

There is evidence that with aging the influence 

of the nervous system on a number of organs 

and body functions is decreased- 19 Several 

studies recently conducted by Russian scientists 

indicated that there were age-related modifications in the metabolism of major biochemical 

transmitters, such as the catecholamines and 

acetylcholine.•• In old age, the biosynthesis of 

these hormones seemed to be decreased, and this 

deficiency was followed by a reorganization of 

their major metabolic pathways. This apparently causes an impairment of the sympathetic 

activity and delayed adrenergic reactions. 

Today, many investigators believe that alterations in the genetic code and protein biosynthesis 

may be intricately involved in cell aging processes. Loss of control of the regulatory genes 

may result in the qualitative and quantitative 

changes, which subsequently bring about agmg 

and death of a cell,45 

13 

Electrophysiologically, the slowing of the 

alpha rhythm has been frequently reported as a 

function of aging, and beta wave activity was 

found to decline. 109• 113• 114 The basic age-related 

change in the electroencephalogram (EEG) occurs predominately along the frequency dimension. The dominant alpha rhythm (8-12 Hz) 

increases with age at the rate of about 4 milliseconds per cycle per decade. Hence, an increase 

of about 15 milliseconds per cycle occurs between 

the ages of 30 and 70 years. There is an accompanying increase in the theta ( 4-7 Hz) and delta 

(1-3 Hz) activity. Although fast beta waves 

(13-25Hz) are prevalent during early senescence, 

they become less frequent with old age. Generally, the average frequency spectrum of the 

EEG in the old is approximately one cycle slower 

than the comparable young adult curve; the peak 

frequency of the alpha rhythm in the older persons is typically 9 Hz.70 
It now appears that the age-associated slowing 

of RT is closely related to the change in brainwave activity.71 Since it has been shown that 

simple RT depends upon the phase of the alpha 

cycle in which a stimulus falls, it can be assumed 

that the increased alpha period may cause the 

slowing of RT with age. Furthermore, the 

alpha cycle may very well be implicated in the 

timing of higher order mental activity, such as 

information-handling capacity and decision making, which are also adversely affected by aging. 

The brain wave pattern of old people was 

found to be more responsive to physical exercise 

than that of the young, although it showed a 

diffuse slowing in cases of advanced senility. 72 • 88 

The percentage of REM sleep remains stable 

until about the age 80 but drops rapidly thereafter.37 Correlations between cognitive and drive 

functions on amount of REM sleep in the aged 

indicated that CNS functions are involved in 

this process. 55 As to the functions of the autonomic nervous system ( ANS), the aged show less 

responsiveness than the young as indicated by 

the galvanic skin response (GSR). 88 

In the area of behavioral sciences, there is a 

definite correlation between the results of neurophysiological tests and chronological age, although there is no evidence of an identifiable 

disease. However, there was also discovered a 

striking similarity between the effects of aging 

and heart disease on psychological test scores, 

which led to the conclusion that impairment of 

cardiovascular functions may be responsible to a 

large degree for the general deterioration of 

performance capacity with age. 95 Table 2 shows 

a survey about the effects of age and cardiovascular disease on various types of human performance. 

There is a typical pattern of psychological 

changes associated with advancing age which has 

a normal neurophysiological rather than patllogenetic basis. ·while some investigators found, 

for example, a correlation of age with both 

psychomotor speed and blood pressure, age-speed 

correlation was higher than the age-blood pressure correlation. Hence, they concluded that the 

trend toward higher blood pressure with advancing age could not be regarded as the cause of 

slowing down the sensory-motor performance. 

Instead, it may possibly reflect a common change 

with advancing age in the regulation of the CNS 

of autonomic and behavioral functions. Patients 

with hypertension and those with coronary artery 

disease appeared to show more psychomotor 

TABLE 2. Some Effects of Older Age and Heart Disease on Performance Measures and Related Physiologic Functions 

(From E. Simonson: Performance as a Function of Age and Cardiovascular Disease. See: A. T. Welford and 

J. E. Birren, 1965.)"'· 118 

Performance and Physiologic Functions 

Max. 02 intake 

Speed of initial increase of 02 in work 

Oxidative recovery Respiratory effic1ency 

Cardiac stroke volume 

Pulse rate recovery 

Endurance, moderately heavy work 

Muscle strength 

Speed repet. movements, small muscles 

Mechanical efficiency 

Endurance, static work 

Motor coordination; small muscles 

larger muscles 

~~; Robinson, 1938 

Reviewed in Simonson and Enzer, 

(3) 1942 

(

4 ) Meakins and Long, 1927 Ko~ig et al., 1962 

(5) Durkin~Mikulicic, 1956 

(6) Landowne et al., 1955 

(7) Dawson and Hellebrandt, 1945 

Age 

Decreased(!) 

Delayed(!) 

Delayed(l,4,20) 

Decreased(l,5,20) 

DecreasedC 6l 

Delayed(l,20) 

Decreased( 7 •8 l 

Decreased(lO,ll,l2) 

Slightly decreased(l 4 ) 

Unchanged or moderately (l 5 ) 

decreased at higher age ' 

Unchanged(9) 

Unchanged(l4,16,17,18) 

Well maintained(l9, 2l) 

(8) 

(9) 

(10) 

(ll) 

(12) 

(13) 

(14) 

Burke et al., 1953 

Simonson et al., 1943 

Quetelet, 1836 

Reijs, 1921 

Fisher and Birren, 1947 

Panfilov, 1963 

Kossoris, 1940 

14 

Cardiovascular Disease 

Decreased( 2 ) 

Del!lyed< 2 ,3) 

Delayed(2/3j 

Decreased 2 

Decreased( 2 ,6) 

Delayed(2) 

Decreased( 2 ) 

Unchanged or slightly decreased(l3) 

Moderately decreased(l5) 

Unchanged or moderately decreased 

dependent on degree of 

decompensation and load( 2 ) 

Probably little change 

Probably unchanged 

Probably li~tle change0 

(15) 

(16) 

(17) 

(18) 

(19) 

(20) 

(21) 

Simonson and Enzer, 1941 

Ascher and Baumgarten, 1925 

Berg, 1947 

Stieglitz, 1941 

Jokl, 1954 

Frol'kis et al., 1962 

Smith, 19~ 
slowing than would be expected from age alone. 

The evidence again points to a separation of the 

effects of disease from a pattern of measurements 

representative of normal neurophysiological aging.95 

Several studies of conduction velocity in 1mman motor nerves have shown that the speed of 

transmission of the nervous impulse is slowed in 

old age.98 However, motor response time seems 

to be remarkably constant for both young and 

elderly persons. Slowness or difficulties in perceiving and transmitting a stimulus results, at 

least partially, in the increase of reaction time 

as previously pointed out, since speed of perception is an important factor in mental activity; 

the decreased mental capacity of the elderly, 

thus, has been explained. The difficulty in accepting sensory input may be related to the inability 

of the nervous system to perceive and interpret 

the incoming information, thus failing to maintain an ongoing "neuronal pattern" in the face 

of fresh stimulus input.16 This loss of capacity 

seems to occur at certain critical stages, particularly at about age 40 and again at age 60.106 

There is also an age deficit in coding and registration of stimulus input material leading to a 

deficit in the retrieval process. Moreover, the 

rate of loss of immediate memory tends to increase with age; i.e., the storage process underlying the capacity for fast recall is subject to 

decay. 22 

It was concluded from the result of a shortterm memory test that the retrieval time became 

longer with increasing age. This slowing was 

thought to be brought about by the increased 

time required to search through the content of 

memory and to initiate or generate the response.3 

In general, the old lose speed and flexibility and 

lack the kind of reserve and coordination that 

accounts for maximum performance of the 

brain. 53 The neural deficit in the aged can be 

largely explained by a decreased number of functionally available neurons, changed cell metabolism, prolonged time for the ideation process, 

and the loss of speed in the retrieval of memory. 

VI. Personality. 

The effects of aging as manifested in psychological, mental, and neurophysiological performance or behavior patterns are in themselves 

related to many alternative conditions and 

15 

factors not considered so far. Some alterations 

of behavior can be caused by or may be associated 

with changes of the personality, temperament, 

motivation, or the value system of the individual, 

or they may depend on some trivial or idiosyncratic elements aroused by the situation. For 

example, it was observed that attitudes and emotional factors influenced performance on a test 

of critical thinking ability. Hence, these variables must be taken into account when dealing 

with the performance of the elderly. The ability 

t.o weigh evidence and critically interpret data 

and changes in deductive thinking in relation to 

age are graphically displayed in Figure 9. 

56 

54 

52 w 

a: 50 0 

u 48 (f) 

I 

1- 46 

44 

42 

40 

0 10 20 

' ' 

30 40 50 60 

AGE IN YEARS 

' ' ' ' ' 

70 

' ' 

FIGURE 9.-Results from 484 subjects, age 12-80 years, 

on the Watson-Glaser Critical Thinking Appraisal 

Test. The solid line indicates ability to weight evidence and interpret data; the broken line indicates 

changes in deductive thinking. (Reproduced with 

permission from Figure 8-1 in Bil-ren, J. E.: The 

Psychology of Aging, Englewood Cliff, N~>w J~>rsey, 

l'r~>ntic~>- Hall, Inc., 1964, 300 pp. Original figur~> in 

Fri~>nd, C. 1\I., and .T. P. Zubek: '.rhe Eff~>cts of Age on 

Critical Thinking Ability, .TOURXAL OF GERONTOLOGY, 13:407-413, 1958.) 

A significant decrease in all measures of flexibility and a significant increase in all measures 

of behavioral rigidity with advancing age were 

reported.' 9 The correlation between the measures 

of mental abilities and personal rigidity were 

significant throughout the adult age span with 

a tendency to decrease toward the upper end of 

the age continuum. There is also a certain possibility o:f a relationship among the effects of 

age, heart disease, and personality test scores, 

implying that impairment of cardiovascular functions may be to a degree responsible for the general decline of performance capacity with age. 118 
It has long been assumed that the aged are at 

a resting state of low internal arousal and sustain 

a low drive state. However, aged persons were 

found to function at a relatively high level of 

autonomic activity (such as blood pressure, heart 

rate, and respiration) when arousal or anxiety 

was heightened by situational circumstances.30 

For example, the performance of older persons 

is in jeopardy under hazardous traffic conditions.10 

The effects of differential reinforcement of 

cautiousness upon intellectual performance m 

older persons were investigated with respect to 

such influences. 3 Cautiousness is often thought 

to be a behavioral characteristic very typical of 

the elderly. Experimentally, this factor was 

manipulated by systematically varying pretest 

instructions involving reinforcement at two levels 

of risk-taking when subjected to the Primary 

Mental Abilities Test. The results confirm most 

of the previous observations; namely, that older 

subjects are usually low risk takers and perform 

better under such conditions. This became obvious only when they realistically exercised their 

option of either responding or not responding to 

the individual task items. 

By using the Edwards Personality Preference 

Schedule, a forced-choice test designed to measure 

the relative strength of 15 needs derived from 

Murray's list of manifest needs, highly significant differences between young and old subjects 

were found on five of these needs.106 On three 

items, namely deference, order, and endurance, 

need scores were higher :for the older subjects. 

On two items, namely, heterosexual activity and 

exhibition, their scores were lower. Marginally 

significant were differences indicating lower need 

for dominance and higher need for abasement on 

the part of the older group. 9 

It has been hypothesized that older subjects 

automatically make most of what capacity they 

may have, and this process has been defined as 

"unconscious optimization." Such behavior is 

often thought to be related to the concept of 

experience; i.e., the ability of the organism to 

adjust through learning. In an experiment designed to investigate age differences in developing the optimum strategy for finding the 

malfunction in a broken -down machine, older 

persons did not show any change of their approach to the problem with increasing time on 

16 

the test, whereas younger subjects did improve, 

indicating a greater selectivity and adaptability 

than the older ones. This was also true in a 

guessing-type experiment. Once again, the old 

subjects showed less of an optimization tendency 

than the younger ones. ~ ot only did the older 

persons behave suboptimally, but their performance fell below that of the youngsters, although 

the older ones had more to lose. 84 

Moral development and moral judgment in the 

elderly have been found to be curvilinearly related to chronological age. Moral judgment rose 

from a relatively low level in preadolescents to 

the highest level in the middle-aged adults. 42 

Thereafter, average stage levels declined. This 

trend was thought to be caused by the elderly 

persons' decreased ability to apply their environmental experiences to their moral judgments. It 

also was theorized that variability in the moral 

judgments of the elderly could be the result of 

an identity crisis associated with aging, the social 

isolation of the aged, and the onset of senility. 

Figure 10 shows how four selected components 

of social age change during a period of four 

decades.81 The analysis of egocentrism as related 

to aging has been based primarily on results of 

perceptual or spatial tests. Elderly subjects 

showed wide individual differences in their 

ability to decenter and decrease spatial egocentrism task performance as compared to 

younger ones.43 In another comparative age 

study, a curvilinear relationship was found between spatial and communicative egocentrism 

and chronological age.83 Finally, a study will be 

mentioned in which age estimates were based on 

the psychological assessment of personality variables. Scores from the Cattell Sixteen Personality Factor Questionnaire (16 PF) were used to 

predict the chronological age of subjects and to 

study the relationships among the ages predicted 

from these measures. It was stated in this context that the assessment of a man's personality 

in terms of a functional age index may also be 

of a practical value for determining career endpoints and retirement planning. 40 

It was found by an analysis of the 16 PF that 

scores from three of the 16 primary factors accounted for 8 percent of the variance of predicted age, namely surgency (F), self-sentiment 

(Q3), and sensitivity (I). A formula expressing 
LESS -1.0 

Chances for 

advancement 

Wife's employment 

20- 30- 40-

29 39 49 

50- 60-

59 69 

Prefered retirement 

LATER 

EARLIER 

Contacts with 

MORE wife's relatives 

LESS 

20-

29 

30- 40- 50-

39 49 59 

60-

69 

AGE GROUPS 

FIGURE 10.-Age changes in mean values (standardized units) of four selected components of social age. (Reproduced with permission from Figure 1 in Rose, C. L.: 

The Measurement of Social Age, AGING AND HUl\IAN DEYPJLOPME:t\T, 3:153-

168, 1972.) 

the relationship of these factors was giVen by 

the investigator: 

Personality age= 

-2.21 Factor F+0.25 Factor Q3 +0.21 Factor I 

+39.17 

The differences with age in the means of the 

measures of the three personality factors are 

given in Figure 11 (right-hand side). The most 

significant ability measures which were part of 

this experiment are shown on the left side. Scores 

on the most important variable, Factor F ( surgency vs. desurgency) , show a tendency toward 

less surgency in older subjects; i.e., they are 

sober, taciturn, and serious. Scores on Factor 

Q3 (self -sentiment) tends towards higher degrees 

of self-sentiment in the aged; i.e., they are 

thought to be more controlled, exacting, and 

socially precise. Scores on Factor I ("premsia") 

indicates a greater sensitivity with increasing 

ageY Figure 11 also shows that in comparison 

with the ability scores the age differences on the 

personality scale are relatively small. Moreover, 

four of the curves have their maximum rate of 

change during the two highest age ranges.40 

17 

Using a somewhat different approach, other investigators identified the factors C, F, G, I, and 

M of the 16 PF as remaining relatively stable, 

with unsystematic age trends for the remaining 

factors. 48 

By and large, the results of this analysis are 

in agreement with previous observations that 

some aspects of the personality structure and 

some of the personality traits are relatively 

stable, while others change 'vith age. 

Accidents. Probably the greatest practical 

implications of human aging in the context of 

this treatise are in the area of personal and 

public safety, since older persons tend to have 

high rates of accidents.• In a related study, the 

average annual death rates from motorcycle accidents were analyzed for the years 1926-1928 

and at decennial intervals until 1966-1968 using 

six age groups. \Vhile the total number of motor 

vehicle fatalities steadily decreased with age for 

persons 15-44 years old, the rate generally increased from age 45 on, reaching its maximum 

with the oldest age groups. Only the 15-25 

year-old males exceeded this group in the two 

latest samples. 
ABILITY PERSONALITY 

··:ro ..... mb~ 

~ 

~ -2.0 

1.0 

__j 

f~ 

·;I~ r~ ~ (03) 

~ ~ 

1:! 

II) 

~ L- "'( "f'" r~ ~ ~ 

"'( 

1.0 

-2.0 

20- 30- 40- 50- J 

20- 30- 40- 50- 60- 70- 29 39 49 59 29 39 49 59 69 79 

AGE GROUPS 

FIGURE 11.-Age changes in the means of three measures 

of ability and three measures of personality that 

Fozard found to be significant predictors of chronological age."' (Reproduced with permission from Figure 

1 in Fozard, .J. L.: Predicting Age in the Adult Years 

From Psychological Assessment of Abilities and Personality, AGING AND HUMAN DEVELOPME.\"T, 

3 :175-182, 1972. ) 

Detailed studies of the nature and cause of 

accidents have shown that those sustained by 

younger people are often due to carelessness or 

foolhardy behavior, whereas accidents of older 

people tend to be caused by slowness in anticipating hazards or in taking action to a void 

them. 78 While it is recognized that circumstances 

and risks are the main determinants of accidents, 

age can cause small differences in coping with 

ensuing situations which may substantially determine the outcome of a hazardous situation. 

VII. Aging and the Human Pilot. 

The process of aging is of a greater significance 

for pilots than for most other occupational 

groups because of the exacting demands of their 

job. As a pilot grows older, the alterations in 

physical and mental fitness may greatly influence 

his professional efficiency. Early detection of 

deteriorations in psychophysiological functions 

and performance of airline pilots is imperative 

to flight safety. Therefore, aeromedical investigations were conducted in this country and 

18 

abroad to determine the effects of age-related 

changes in older pilots and to assess their implications.119 

A. Performance J}f easures. In an early study 

( 1953) on U.S. Air Force pilots using the 

"critical-incident technique," it was found that 

the physical abilities of aircrew members decreased with age, particularly the ability to resist 

fatigue and sustained demands upon the human 

organism.89 Actual job performance deteriorated 

particularly with respect to speed and accuracy 

of work and corrective action, control in emergency situations, and-surprisingly-retention of 

a proportionate degree of caution. There were 

some indications that the relationships of the 

older crewmembers with the rest of the team 

became poorer. Also, the ability and motivation 

to improve in skill and technique were found to 

decline, and motivation and adjustment in regard 

to the job in general were negatively age related. 

In later investigations conducted by scientists 

in the U.S.S.R. on two groups of pilots (30-39 

years and 40-50 years) . no differences between 

these groups were found concerning simple RT 

and speed of the "basic nervous processes. " 18 

There was no impairment of short-term visual 

memory in the older subjects. There was also 

no decrease in the interpretation of visual stimuli, and no differences were found in the information-processing ability between the younger 

and older pilots. 

It was reported, however, that the older pilots 

needed longer times to shift their attention and 

that the overall performance declined with increasing age at the higher levels of information 

input. Nonetheless, the older pilots seemed to 

adopt a more efficient strategy in signal detection; it was thought that this outweighed, at 

least partially, some of the limitations imposed 

by the peripheral end of the visual pathway. 

The results of a longitudinal aging study on 

pilots conducted by the Lovelace Foundation for 

Medical Research and Education showed that 

visual accommodation, clark adaptation, and 

auditory functions are impaired with age.' 5 

In a sampling of over 100 professional pilots, 

it was suspected and concluded that their responses to sudden emergencies under conditions 

of information overload became less and less 

adequate as they grew olcler.100 It is equally 

clear that, insofar as skill proficiency can ever 
be evaluated outside the actual flying situation, 

the routine aspects of the professional pilot's 

skills seem likely· to be affected by aging. It 

was reported that pilots over age 40 are relatively more susceptible than the younger ones to 

the effects of information overload when other 

activities intervene during the period of information acquisition.101 

It is difficult to find dependable criteria by 

which the effects of experience, such as judgment, 

insight, and comprehension of the task on performance, can be measured. The subjective 

assessment of job performance indicates that the 

overwhelming majority of older pilots do not 

notice increased weariness during routine duties 

or transit training nor show forgetfulness, 

absent-mindedness, or ineffective performance in 

flight.54 However, it was found that the restoration of "higher nervous activity" after extended 

flights (10 hours) to the original level took 

longer in the older pilots than in the younger 

ones. This was demonstrated by the EEG records obtained from the older pilot group. 

B. Neural Functions. The analysis of clinical 

and physiological functions of senior pilots of 

the civil air fleet in the U.S.S.R. yielded very 

delicate changes in the motor coordination in 

pilots over 45 years of age. 54 The higher nervous 

activity, visual discrimination, and some psychological functions showed that the older pilots 

were not as readily adaptable to new situations 

as the younger ones. In contrast, they appeared 

to be psychologically more stable. Although 

visual memory did not deteriorate with age, 

their capacity and concentration of attention 

tended to decrease slightly. The functions of 

the vestibular apparatus of the inner ear and its 

effects on motion sensitivity and motion sickness 

were unrelated to age. 

Measures of "reserve channel capacity" and 

psychophysiologic thresholds revealed that, in a 

sample of 250 active pilots, age differences were 

less impressive than would be expected from 

gerentological studies on the general population.102 However, "overload conditions" of the 

information channels indicated a small but consistent negative correlation with age. This condition has been interpreted as an increased noise 

level in the central nervous system of the older 

pilots. 

19 

C. Jvfedical and Psychological Interactions. It 

also seems that the individual differences among 

airmen in some of the relevant modalities of 

performance are related to their cardiovascular 

status.103 This suggests that the performance 

degradations in a high-grade skill are more 

likely to depend upon the age-related efficiency 

of the pulmonary and cardiovascular system 

than upon age as such. Persons suffering from 

arteriosclerotic coronary heart diseases or showing evidence of old myocardial infarctions and 

those with essential hypertension performed 

more poorly on a wide variety of psychological 

tests than did reasonably well-matched, healthy 

subjects.104 The incidence of cardiovascular diseases and their increase with age are high enough 

to account for much of the decline of psychological and mental functions in older pilots. 

However, there is undoubtedly much more to 

aging than cardiovascular or other related diseases.95 

D. Age and Aircraft Accidents. In a 1967 

FAA report concerning aircraft accidents by 

older persons, it was reported that total accident 

rate is lowest for the age group 16-29 years, 

highest for the age group 30-43 years, declines 

for the group 44-59 years and rises only slightly 

for ages 60 and older. 60 • 63 However, more recent 

statistical analyses of accident data revealed that 

the accident rate increases quite rapidly after 

age 59 and reaches its maximum after age 70 as 

shown in Figure 12. Such data, however, must 

be interpreted in terms of the "exposure time" 

of subjects in each age group. 

VIII. Summary and Conclusions. 

Human aging is a biological process with profound implications on performance and proficiency. Although there is evidence that the 

occurrence of cardiovascular incapacitation and 

the number of accidents and deaths in aviators 

increase drastically after age 60, the actual cutoff 

point of the pilot's career due to aging has not 

been scientifically established. In order to arrive at some reliable criteria for retirement from 

flight, large numbers of pilots have been studied 

in the past in several countries through medical 

examinations and by physiological and psychological tests. In the United States, there were 

three longitudinal studies conducted on airmen, 

of which the One-Thousand-Aviator-Study is 
120 

c: 

Q) 100 E 

... 

~ 

0 

0 

0 

80 

0 

... 

Q) 

Q. 60 

w 

t-

~ 

a:: 

t40 

z 

w 

0 

u 20 u 

~ 

0 

< 20 20-29 30-39 40-49 50-59 60-69 > 70 

AGE (Years) 

FIGURE 12.-Age and accident rates in general aviation pilots (1974 data). 

3till pursued at the U.S. Naval Aerospace Medical Center in Pensacola, Florida. However, the 

attempt to assess the pilot's critical functional 

changes due to aging in the rapidly changing 

aviation environment over long periods of time 

and to apply the findings to the determination 

of career endpoints presents formidable methodological and practical obstacles. 

Different approaches have therefore been used 

to determine the physiological and psychological 

effects of aging and their relationships with 

flight safety. In 1953, a study conducted by the 

American Institute of Research for the United 

States Air Force was published, in which the 

critical incident technique was used to define behavior that was thought to be affected by age. 

Five years later, scientists developed a battery 

of psychophysiological tests for the assessment 

of age-related changes in aircrew performance. 

It was found that the physical abilities of the 

crewmembers decreased with age, particularly 

the capacity of the human organism to resist 

fatigue and sustained demands. Measures of 

mental and neural functions taken by scientists 

20 

at the Lovelace Foundation for Medical Education and Research on a sample of 250 active 

pilots showed that reserve channel capacity and 

task overload conditions correlated negatively 

with age, the fact notwithstanding that most of 

the pilots were below the age 60. By and large, 

systematic investigations and factor analyses 

concerning functional age changes and aviator 

proficiency of older pilots are not aplenty. 

In the area of behavioral sciences, psychometric measures have been used successfully for 

assessing age differences. Excellent surveys of 

the state of the art were given by Dennis (1953) 

and recently by Schaie and Gribbin (1975) .

28 • 85 

The latter concluded that the psychology of 

aging has matured a great deal during the past 

5 years. There has been a significant shift of 

interest from measuring differences towards the 

direct explication of age changes by means of 

descriptive as well as experimental strategies. 

Moreover, dissatisfaction with chronological age 

as the independent variable in gerontological 

studies has led to an examination of the concept 

of functional age. Functional age would be a 
convenient method to apply to problems of variable retirement. The wealth of information 

available in the fields of experimental psychology, 

applied physiology, and gerontology can be consulted in this effort. They show age-related decreases in a wide variety of functions, such as 

reaction time, memory, complex performances, 

manual skills, visual, tactile and auditory perception, cognitive and mental abilities, learning 

and other processes in different population 

samples including experienced pilots. 

Generally, abilities to perform highly skilled 

tasks rapidly, to adapt to new and changing environmental situations, to resist fatigue, to maintain physical stamina, and to perform effectively 

in a complex and stressful environment begin to 

decline in early middle life and continue to decline at a fairly steady rate thereafter. 

One of the most critical requirements in regard 

to pilot performance-namely, information processing-is jeopardized in older pilots because of 

the risk of "overloading" of the channel capacity 

of the central nervous system. The extent to 

21 

which retained experience, judgment, and reasoning abilities tend to counteract the functions 

which do deteriorate has not been adequately 

determined. The point which is critical is that 

at which the compensatory mechanisms fail to 

neutralize the deteriorated functions in older 

pilots. The piloting of aircraft then may become hazardous. The studies reported and reviewed fail to indicate how that point can be 

identified. 

There is no "psychophysiologic age index" 

available that can be reliably applied for 

determining the performance of airline pilots. 

However, the development of such an index appears feasible and therefore should be pursued. 

At present, the psychophysiologic cutoff point 

of the age-related performance-degradation curve 

for pilots has not been determined. The findings 

of this survey suggest that some of the critical 

functions deteriorate during the sixth decade; 

some persist after the age 60 is reached. As a provisory solution to the age problem in the cockpit, 

it is recommended that older captains should 

always be paired with younger pilots. 
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24 

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