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Volume: 18 Issue: 4

Month/Year: 1976Pages: 257-63

Article Author: Colquhoun P

Article Title: Psychological and

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ACTIVITAS NERVOSA

SUPERIOR

I~~-L. 18

DECEMBER 1976 F ASe. 4

Avicenum, zdravotnické nakladatelství, n. p., 1975

PSYCHOLOGICAL

AND P S Y C HOP H Y S I 0 LOG IC A LAS PEe T S

o F W 0 R K AND FAT I G U E 1)

(A rev i e W 0 f pap e r s pre s e n t e d a t P C - I AOH Sub-Committee meeting on Higher Nervous

Fun c t ion s, P rag u e, J u i y, 1 9 7 5 )

P. Colquhoun2)

INTRODUCTION

As defined by one of the speakers at the Prague meeting, the general aim

of this area of research is the assessment of the consequences for the worker of

the mental demands arising from his work, by quantifying changes in those

physiological variables that are influenced by psychological stimuli.

The problems posed by this statement of aim are numerous and complex,

and most of them were ilustrated in one way or another by the Prague contributions. Perhaps the most pervasive problem is that of individual differences.

Patterns of physiological response to a given work situation vary widely in

diferent people; on the other hand, there is encouraging evidence that anyparticular person is relatively consistent in his response pattern when presented

with the same work situation on different occasions. If, then, we could identify

those variables which would give us, as it were, a "baseline" for a particular

individual, we would have gone a fair way towards a solution to the problem.

There is growing evidence that per son a lit yfactors, particularly those of

iritroversion on the one hand, and anxiety-level on the othér, are of considerable

relevance to individual diferences. These personality factors may influence the

relationship between "tonic" and "phasic" psysiological activation levels, and,

in turn, this relationship is likely to affect the way in which a person actually

performs a particular task during a period of observation.

Successful identification of personality type, however, may not provide the

whole answer. Physiological response patterns to a particular task, or to changes

in performance demands within that task, occur against a background of overall

I) A report at the 18 th International Congresl' of Occupational Health, Brighton, England,

September 1975. Session No. 32: Environmental and Psychological Stress.

2) MRC Applied Psychology Unit, University. of Sussex, Brighton, England.

257
response to the t0'tal w0'rk situation which is partly the result of the individual's

past experience. Although it may well be true that the nature of this "long-term"

reaction wil itself be dependent to a substantial extent on intrinsic personality

factors, it is also the case that the O'verall characteristics of the job, the social

structure of the workf0'rce in the factory, and even the way the worker views

his work in be c0'ntex of his general life-pattern wil all have affected the

individual's basic physi0'logical response by a 'process of extended conditioning

over a period of perhaps many years.

Whilst acknowledging the importance of these long-term underlying response

patterns, we should not be deterred by the magnitude of the problem invO'lved

in defining them from continuing to search for physiological correlates of

objectively measureable changes in work demand, or of clearly different types

of performance; because success in identifying such correlates at a predictive

level would at least enable us to' make a practical start towards the improvement

of working conditions. Demonstration of the occurrence of critical physiological

response patterns in a group of workers engaged in a particular form of work

would point clearly to the need for changing the way their tasks were organised.

This would provide a strong argument for a thorough appraisal of the jobs

involved in terms of their ergonomic and social characteristics. Hopefully, this

would then lead to a scientific redesign of the work-system as a wh0'le.

THE CONTRIBUTIONS

"p s Y c h 010 g i c a 1" s t u die s. Broadly speaking, one c0'uld distinguish

two kinds of w0'rk situatiO'n which had been experimentally studied by the contributors to the Prague symposium, These were designed to investigate, on the

one hand, the psysi0'logical changes that occur simply as a function of t i me

in a particular work situati0'n - perhaps involving a task of the "vigilance"

il "monitoring" type, in which in one sense it could be said the subject is

consistently un d e r 1 0' ad e d - and, on the other hand, changes resulÜng from

v a r y i n g the d e g r e e of load within a particular task, sometimes up' to

the point of 0 v e r loa d. Several diferent tasks were used in these studies.

Besides these task diferences, there were even greater differences in the

physiological variables measured. Again, these fell into two broad categories -

measures of central nervous function on the one hand, and 0'f autonomic function on the other. Sometimes both were studied together. In some cases the choice

of variables gave the appearance of having been 20mewhat haphazard -

depending, perhaps, on the investigators' own theory, or (possibly) on the

equipment available in his laboratory. But perhaps this is a little unfair; at

this stage, in the area we are discussing, almost a 11 information is potentially

usefuL. The problem comes when one tries to interpret it, particularly in the

absence 0'f an adequate model which attempts, to relate actual performance to

concurrent changes in both central and autonomic variables which are themselves

related, and makes specific hypotheses about such multiple relationships. An

associated difficulty is "what is the best method0'logy to apply to the analysis of

the mass 0'f data that can be collected even when only 0 n e variable is being

measured?" There are many diferent ways of analysing, for example, data on

"sinus arrhythmia" - but happily one crf the ~peakers suggested a technique

for solving this question 0'f "h0'w to analyse" 51ch data, which may turn out

to be of considerable value for general use.

To turn now to details of particular contributions, we might start with two

related papers from the Laboratory for Ergonomic Psychology of The Netherlands

258

I

I

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1

Organization f(

13. W. Hyndm

binary choice

pace of work j

1 minute 'with(

to a neon flas:

made before a

of the visual e,

to information

variability, the

increase. in am

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to be compose

electrical, and

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were highly s(

-acting factors

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with blood-pn

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nism 0'f this

of endocrine

central and a

Simultán

nerv0'us func1

colleagues fre

at changes in

by varying tl

perf0'rmed. Tl

included two

amount of ii

patterning wI

to demonstrai

also. There v

EEG pattern

and again as

changes in re

of the compc

also, t0' some

the changes i

hO:wever the

Uonship.

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ta~k in conj

eye-blinking.

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the individual's

:his "lang-term"

n~ic persanality

: Jab, the social

ie worker views

le affected the

led conditioning

erlying response

roblem involved

ll correlates of

different types

at a predictive

he improvement

al physiological

r form of work

were organised.

:al of the jobs

Hopefully, this

a whole.

Juld distinguish

ied by the COIestigate, on the

iction of t i il e

the "vigilance"

the subject is

s resulting from

ometimes up. to

iese studies.

ferences in the

id categories -

IUtonomic funccases the choice

haphazard -

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little unfair; at

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ample, data on

ed a technique .

i may turn out

start with two

'he Netherlands

Organization for Health Research in Amsterdam, presented by J. L. Blom and

B. W. Hyndman. Their technique is to use what they describe as a "100 %"

binary choice task of paced pitch discrimination. "100 %" means setting the

pace af work for the subject at the rate at which he can perform the task for

1 minute 'without error. While performing the task, the visual evaked response

to a neon flash repeated at 2 second intervals is recorded; recordings are also

made before and after the task period. Selection Wave iv as the component

of the visual evoked response that they had previously found to be most sensitive

to information processing, they observed that, despite large inter-individual

variability, the a v era g e d Wave iv from a group of subjects sho.ws a marked

increase in amplitude during the task, and also, very interestingly, a prolanged

recavery period lasting approximately 35 minutes. This recovery curve appears

to be composed af a primary rapid phase, which the authors hypothesise to be

electrical, and a secondary, much slower phase, presumed to be biochemicaL.

The authors fonnd that the reactians to the task, and the recovery curve, were

i n t r a - i n d i v i d u a 11 y quite stable, but (significantly) admit that they

were highly sensitive to what they describe as "emotional and extraneous long-

-acting factors".

During their experiments Blom and Hyndman also recorded heart rate.

Acting on their theory that the signal produced by low-pass filtering af the

cardiac event sequence is the physialagical counterpart of autonomic activity

converging on the sin0'-atrial no.de, they showed that the relative spectral po.wer

of the 7 -10 sec0'nd period band (which corresp0'nds to. the range associated

with blood-pressure homeostasis) was significantly depressed up to 35 minutes

after completion 0'f the task. They n0'te the similarity 0'f the recovery pattern 10

that o.f Wave iv 0'f the visual evoked response, and conclude that the mechanism 0'f this persisting post-task effect is probably associated with the activity

of endocrine processes, which (in their words) "in turn affects the activity of

central and autonomic nervous systems alike".

Simultaneously recording, in this case, two measures af c e n t r a I

nervous fnnction (EEG and the auditory evoked response), E. Ott0' and his

colleagues from the Central Institute for Occupational Health in Berlin looked

at changes in these measures when responding to different mental loads produced

by varying the speed with which a 6minute mental arithmetic task had to be

performed. They examined time-dependent changes over a one-hour period which

included two cantrol conditions and showed that both time period, and the

amount of information load, produced significaut differences in the EEG

patterning which were indicative of changes in activation leveL. They were able

to demonstrate that these differences showed up wit h i n each 6-minute period

also.. There was a significant mono.tonic trend towards desynchronisation of the

EEG patterning as load increased from resting up to fast, paced, performance,.

and again as time on task increased. In the case of the auditory eVo.ked response,

changes in respo.nse to the task requirements were found only in the peak latency

of the component P2, which shortened monotonically with increasing load, and

also, to some extent, whith time on task. Thus a parallelism was shown between

the changes in the EEG and in particular aspect of the auditory evoked response;

hawever the authors do nat comment on the significance of this apparent relaÜonship.

In contrast to the papers just described, N.Roth (of the Paul-Flechsig

Institute of Brain Research in Leipzig) used a mat or , rather than a mental

task in conjunction with recordings of EEG, heart and respiratory rates, and

eye-blinking. The ta~k was one of tracking the deflections of an osciloscope

259
beam; this task was alternated with a visual reaction-time task in which feedback

of performance was given to the subjects. A particular aim of this experiment

was to examine, under strictly controlled laboratory c0'nditions, the relationship

between individuals' resp0'nse patterns and factors intrinsic to the pers0'n such

as extraversion, anxiety, m0'tivati0'n and risk-taking levels.

In the tracking task, it was found that the extraverts performed the task

better than the introverts, and were less variable. Adaptation to the sequence

of trials as shown by a decrease in heart rate just before the expected deflection of the osciloscope beam, and by the occurrence of alpha activity in the

inter-trial intervals, was more distinct in highly-motivated extraverts. By contrast,

subjects with high anxiety and with what the auth0'r describes as "undirected

expectancy" showed increased heart, respiratory, and blinking rates without

adaptation to the sequence of trials, and also less EEG alpha activity.

In the reaction-time task with feedback, the adaptation to the sequence of

trials was again more pronounced in extraverts. Risk-taking scores were also

found to be related to performance, in this case to the probability of responding

to a non-signal stimulus (a "click" occasionally inserted 0.3 seconds before the

visual stimulus). Anxious subjects again showed higher levels of activation

throughout the experiment.

M. Horváth, E. Frantík, K. Kopriva and J. Meissner (from the Institute

of Hygiene and Epidemiology in Prague) have concentrated on a laboratory

situation which models practical tasks requiring only infrequent, small, and rapid

control- actions by the operator - in other words, a vigilance-type task. Sometimes a secondary tracking task is added. Typical of the main vigilance-type

task was one in which maintained attention was required to auditory stimuli

presehted at irregular intervals and at varying intensities through each of two

earphones in such a way that the signals were perceived as emanating at diferent

spatial locations away fr0'm the mid-line. The subject had to respond to those

signals which did not appear to be in the mid-line, while performing a secondary

visual tracking task, ina testing situation which was deliberately arranged to

be maximally m0'n0'ton0'us, and which c0'ntinued for about one hour.

The performance of over 80 % of subjects deteriorated in these conditions,

mainly in respect 0'f an increase in failures to detect signals with time on task,

and a slowing of response-time. This is the typical "vigilance decrement function", and in this experiment this decrement was shown to be accompanied by

an increase in the amplitude 0'f EEG theta waves, indicative of a sleep-like

state. A test-retest correlation 0'f 0.69 was found for this task - which shows

its reliability, and a correlation of 0.60 with subjects' reported ability to maintaih

vigilance in a reallife situations - which demonstrates its validity.

A meth0'd of detecting the effects of fatigue and stress (and also, incidentally,

of chronic intoxication with various neurotropic drugs) using the electrodermal

reflex, was described by i. Dumitrescu of the Centre for Protection and Hygiene

of Work of the Ministry 0'f Industrial Chemistry in Bucharest. The technique

used enables separate calculations to be made of the various components 0'f :the

reflex. These comp0'nents are considered to make up the time required for

crossing a multisynaptic circuit and represent (i) the afferent time, (ii) the

central efferent time (iii) the peripheral efferent time and (iv) the peripheral

effector or "glandular" time. The prop0'rtions of the total reflex time accounted

for by these diferent components .was shown to. vary in different states, the

central efferent time, for example, increasing relative to the 0'thercomponents

in fatigue states, and acc0'unting for m0'st of the overall increase in hitency

observed in this situation.

26Ó

Method0'lo:

have already seen ,

The quantification 0

problem in some cas(

in Amsterdam, sugg

would be to retrievi

possible, and in the

only do different em

cular physi0'logical v

physi0'l0'gical reactio

those aspects 0'f the

kinds of stimuli pn

be identified it woul

The first 0'f the

üf a correlation mat

the single variable

variance could be ei

The second aim. wa

üf change in each ~

opposed to' resting. j

each üf these scores,

scores for this partÜ

v a ria t i 0' n 0'f thi

seem to have gener

besides sinus arrythi

S t u die s of

The papers mention(

siological" , and as

responses. Other c0'r

or intrinsic states 0

üther.

One of the mo

C. Teiger and A. L

Ergonomics in Paris

through a particular

latter with a stationa

as well as younger

are clear! y diferent

Thus 0'lder subjects

which are themselve

larger and more var

and more variable i

age changes reflect

tion into kinaesthetii

in which their spatia

keep these frames of

remain accurate. Cle

task studied, but of

of work is faster, (

adjustments is neces

A different fac1

by V. Brichácek anc
261

Met hod 0 log i c a I Pro b I ems. In the papers mentioned so far we

have already seen a variety of different physiological measures being used.

The quantification af some of these variables presents a major methodological

problem in some cases. C. Opmeer, of the Laboratory for Ergonomic Psychology

in Amsterdam, suggested a two-way approach to this problem. The first aim

would be to retrieve as much of the information present in the variable as

possible, and in the most economical way. This is very important, since not

only do. different environmental situations influence different aspects of a particular physiological variable, but individual peaple also often show idiosynchratic

physiO'logical reactions. Opmeer's second aim would be the determinatian of

thO'se aspects of the variable in question that are mO'st sensitive to the different

kinds O'f stimuli present in the working environment. If these aspects could

be identified it would then unnecessary to use the remaining scores.

The first of these aims was ilustrated by the results of a factm analysis

of a correlation matrix of 25 scores calculated by a computer programme fO'r

the single variable sinus arrythmia. It was found that about 80 % of the

variance could be explained by 5 factors which were deccribed by the author.

The second aim was ilustrated by using the same 25 scores and a criterion

of change in each score when performing an auditory binary chaice task, as

oppased to resting. A rank order was abtained for the diferentiating power of

each of these scores, and by this method it was found that the most sensitive

scores for this particular task were the ran g e an the c 0 e f f i c i e n t 0 f

v a ria t ion of the interval times. This two-way approach of Opmeer would

seem to. have general value for application to other physiological measures

besides sinus arrythmia.

Studies of "long-term" and "psychological" factors.

The papers mentioned up till now could be generally described as "psychophysiolagical", and as being concerned primarily with relatively short-term

responses. Other contributions at Prague were concerned with more long-term,

or intrinsic states on the one hand, and with "psychological" aspects on the

other.

One of the more. obvious of these "long-term" factors is of course, age.

C. Teiger and A. Lavile, O'f the CNAM Laboratory of Work Physiology and

Ergonomics in Paris showed that, in a learning task involving punching holes

through a particular pattern of circles on a moving target by comparing the

latter with a stationary model, subjects aged between 35 and 45 actually perform

as well as younger subjects between 18 and 25. However, the twO' age groups

are clearly differentiated in the way in which this performance is effected.

Thus older subjects are slawer in making the necessary postural adjustments,

which are themselves smaller and made less frequently. They also make fewer,

larger and more variable ocular fixations af the model, and have much longer

and more variable inter-fixation time intervals. The authors suggest that these

age changes reflect increasing diffculty in rapidly translating visual information into kinaesthetic information, which leads older people to modify the ways

in which their spatial frames of reference are constructed. They wil tend to try to

keep these frames of reference stable in order to ensure that their motor responSes

remain accurate. Clearly this change O'f strategy was successful in the particular

task studied, but of course it may not work in other situations where the pace

of work is faster, or a more complex pattern of eyemovements and postural

adjustments is necessary.

A different factor, this time in the "psychological" area, was investigated

by V. Brichácek and colleagues at the Charles University in Prague. They were
concerned with the behavioural, physiological, and subjective components of

what they term "negatively oriented tension", which may of course be a chronic

condition in some individuals. However, since they considered that reliable

methods for detecting this state "in the field" are not at present available

they induced this tension experimentally by aversive conditioning techniques:

using expectation of electric shocks. As might perhaps be predicted, activation

levels (measured by pulse rate and GSR) were increased under this induced

negative tension. However, of a number of different psychological tests given,

some were not affected at all by the tension, whereas others were. Thus reaction

time was shortened but, in accordance with a hypothesis of the authors, in

a projective test more photographs of people were classified as producing feelings

of antipathy in the subjects. The general idea behind these experiments was

that the more test (or work situation) is unstructured, the greater the probability

that aversive reactions to the task wil occur in people with negative emotional

tension. Since it was found that there was a "carry-over" effect from the

tension condition to the control condition, the authors suggest that 

the past

stress experience of an individual wil affect the way he responds to any work

situation with which he may be confronted, and that aversive reactions may

be expected if the situation is relatively unstructured.

A similar conception follows from a pilot study described by M. Horvath,

O. Kovalik and E. Frantik from the Institute of Hygiene and Epidemiology,

Prague. This study forms the basis of a longitudinal survey of occupational

mental hygiene in technical resarch and development workers. Although the

work of research workers does not usually involve occupational hazards in 

the

traditional sense. nevertheless their mental performance is affected by a number

of factors. An analysis of the influence of these factors was based on the hypothesis that the creative effciency of this kind of worker depends on an intensive

activation of higher nervous functions, which may easily switch into negative

emotional tension. This tension affects primarily the creative rather than the

routine components of the working activity, it increases the risk of exceeding

the person's adaptability, and may give rise to states of maladjustment and

psychosomatic disturbance in predisposed individuals.

A correlative longitudinal study is about to be initiated, involving on the

one hand the determination of those external factors adversely affecting work

comfort and mental condition, life style, personality traits, and habitual

behavioural patterns; and, on 'the other, measurement of subjective pressures

and tensions, somatic and psychic sPate, physical fitness and autonomic reactions. The aims are to elucidate (a) which of the factors do not form an indispensable part of the actual job and whether their removal could improve working

conditions, and (b) the best best ways (preventive measures, counselling, etc.) to

counteract the negative effect of the remaining factors in order to maintain an

optimal mental condition.

D. A. Vasilescu and i. P. Vasilescu of the Ministry of Transport in Bucharest also talked about "stress". The purpose of their paper was to introduce

the concept of "interpersonal" stress, which describes the action of any stressing

agent on a group of people, as opposed to its action on an individuaL. The effect

of this stress can be measured using sociometric techniques; thus the authors

consider that it could also be called "sociometric" stress. They see it as a type

of "superindividual" stress, which is not necessarily dependent on the stress

effects occurring in a particular person (the sort of situation most frequently

studied up til now). In the groups that had been studied in stress situations

almost all the classical sociometric indicators seemed to be sensitive to the

262

action of t

relations v

tion of or!

nient of s

" aggressOl

in a secOl

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the socior

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range of

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CONCLUSIONS

I t should be evident from the foregoing account of the Prague papers that,

particularly in the "psychophysiological" area, an almost bewildering variety

of physiological measures are being investigated, along with a considerable

range of work tasks. Some of the technical aspects of the research indicated an

extremely high level of sophistication, which the use of automatic devices for

recording both digital and analogue data, associated computer facilities for

handling this data, and complex programming for subjecting the results to

advance forms of statistical analysis. All this is very encouraging, in that it

demonstrates that we are now in a position to make very accurate and detailed

records of a large number of highly specifc variables in many different situations. The questions one is left with, however, are: w h i c h variables? - in

w h i c h situations? It would seem that there is now a pressing need for carefully formulated hypotheses about the relationships between selected aspects

of performance at specific types of task, and changes in particular central and

autonomic variables - hypothese that can now be tested with the new technologies. Without models on which such hypotheses can be based, we may bp

in danger of being overwhelmed by a feast of information which could easily

defy digestion, let alone interpretation. It wil be interesting to see, when wp

have heard the other contributions to this present meeting, whether this view

is held generally by the participants here.

of

iie

iIe

Ie,

~S,

)U

~d

action of this sociometric stress, and indices based on perception of interpersonal

relations were found to be particularly sensitive, The three phases in the evolution of organic stress described by Selye could also be identified in the development of sociometric stress, induced by, for example, what the authors call an

"aggressor factor". This could act in a primary way to produce the stress, or

in a secondary way in the sense that the aggression first causes a stress reaction at a level other than the sociometric one, and this reaction in turn produces

the sociometric stress.

h,

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263