Laboratory studies of repetitive work

Acta Psychoiogica 29 (1969) 268-278; 0 North-HolEandPublishing Co., Amstercibm Not to be reproduced in w formwithoutwrittenpexmkionfromthe publisher IAB0WimRs.Y

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IV, AUTO-AROUSAL AS A DETERMINANT OF PERFORMANCE IN MONOTONOUS TASKS K. F. W. MURRELL University of Wales Institute of Science and Technology, Card@, Wales

proposal (MLIRRELL, 1967) that performance changes on continuous ati mon&m~~ tasks could be explained by the prod~ti~ of hy.per-arou& by aiuto-aroti is now rejeoted. Evidemx is prese&xi which sug,ge& that auto-arousal dms occur and ‘that it is the consequent “damping down” corticofugal projections whidh cause the observed changes in performance. An

earlier

0ur present laboratq

research programme started in ‘4pril 1962, using a simulated indu&rial task of inspectOn of electrical components; up Gil n.ow 21 subje& have been tested who have been employed on day-rate wages for periods of 3 or 4 months. They work for 4 hours a day under varying conditions on a $ask which is both continuous and monotonous. We started by inves&gatiug the suggestion put forward by BARTLETT (1953) that “psychulogical fa@ue” is indicated by the appearance of irregul&ies in a mntinuous task. Wtt have confirmed that irrq@rities do appear (WRRELL and FORSAITH, 1963; MVRRELL, 1965). There are, natura&, with&subject aud betweensubject differences in the time of appearance of .irregu&rities; summation however will g.ive trends’, aud irregularity will typically appear after one hour of a codnuous working period of 3% hours (fig. 1).

Hours

Fig. 1. %.bje& B. Long timers(i.e. cycle times more than 2 S.D. from mem) in each 15 min over 10 days. 268

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cited, but what is unexpexted is that thereafter recovery of regularity followed by a second period of irregult one hour later, m s pattern of aviour I started at all cominuous tasks have something in ve assembly tasks or inactive mtitoring tasks 967). The former type of task has been very little not ,ts have been discussed theoretically. Work on vant, but is usually too short-term for our s, on the other hand, have b%n extensively icd and a series of hypotheses have been developped to explain ormance with time. These can act as a useful starting point. Vigilance hypotheses appear to be of three kinds: (1) SPrategicaZ. The expectancy theory of BAKER (195P), the observing responses of HOLLAND(1958), varisus statistic& appoaches of the kind enunciated by BRO~.DBENT (e.g. 1963). (2)

Behuviaural. Inhibition.

(3)

Neurolugical. Activation or arousal.

Inhibition can be discarded at the ou‘tse. as being too vague, it is a woolly word to exphain e&!&s which can equally well be explained on CI neurological basis. Neurolo$cal and strategical hypothesis are not mutually exclusive; strategical hypotheses are probably specific to vigilance cl;ndcannot IX: used as an explanation of active performance. This leaves only arousaL JERISON(1967) in a critical appraisal of the Carousaltheory of vigilance has said “the activation concept has been so broad it is rather di%cult to get experimental results that are beyond its ken”. LACEY (1966) has further pointed out that EEG, EGG (autonomic), skin conductance and behavioural measurements may all give results which appear to be independent; that variable and inconsistant relationships betwem these functions occur within one individual which appear to be unrelated to arousal patterns; thus, generalized behaviour is difhcult to specify. Unfortunately this has also ,been our experience since we have been unable to see any consistent relationships between the diierent measures which we have been making. On these grounds, then, we might be justified in abandoning attempts to relate our ob-

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served behaviour to arousal. But Jerison went on to say “it is certainly the case that activation or arousal plays a significant role in vigilance performance”, and so it has been our view that we should nut abandon arousal simply because of difliculties and ,the presem absence of easy success. I first put forward at a meeting of the Bedford Group a tentative theory which could account for the behavim which we had observd (MURRELL,1966). It is in some ways similar to the theory put forward at the same time as BERGUM (1966). I proposed that continuous are basically non-arousing and, ;therefore, auto-arousal is necessary to maintain performance (a definition of auto-arousal will be found in MURRELL, 1967). This auto-arousal will push up the arousal level which passes through ‘the zone of good re,gular performance into the hyper-arousal area and that it is then that the irregularities will occur. In order to maintain homeostasis there must be a damping down of arousal and this will cause the arousal level to fall back into the zone of regular perfor.mance, (to give an inverted U-shaped curve). The damping down may at the same time cause the extinction of the downward auto-arousal projections so that the level of arousal will contiuue to fall until it goes below the optimum and irregularity will again occur. This suggestion would account for the appearance of irregularly, the reappearance of regularity and the second phase of irregularity. It is probably too simple an explanation, there may be more ,than one mechanism at work, but it does provide a useful starting point for reviewing the evidence which is available. Siice we cannot measure the activity uf the reticular formation directly in humans we must use some indirect measure and it seems generally accepted that skin conductance is at least an approximation to arousal in the human. In the discussion which follows, therefore, I shall deal primarily with skin conductance. EVIDENCEor: HYPER-AROUSAL

‘WC%a~ found in a number of ,instances that there are inverted Us@ed conductance curves, but the peaks of these curves generally appeared before the onset of irregularity which tended to occur either near the trailing edge of the U or when the conductance was falling. But quite often there were no U-shaped curves at all. There m.ay be a continuo~ rise ig conductance, level conductance, or a continuous fall in conductance after the initial warm up. But even so the irregu-

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MONOTONOUS TASKS

There is mrne evidence that irregularity may bc or may occur when conductance is low. ve to explain why performance actually roves over a ’ n conductance has not risen. dence obtained in the last two years, it seems r-arousal theory must be abandoned; evidence from further experiments which m.ay lead to the development of ideas will now VIDENCE FROM

BINED

ACT.IVITY/VIGILANCE

EXPERIMENTS

riments the: basic task was retained with a “vig&mce” e meti employed was similar to that used by which a small light was fixed to the he.ad so that it was in the periphery of vision. The light came on 12 times in each hour and remained on for 10 seconds or until it was extinguished by the subject using her spare hand (the basic task is one-handed). Different sequences of presentation were used so Ithat after 5 sessions a signal had occurred once in every minute of an hour. There were relatively few actual missed signals but latency provides a weful measure and as might be expected there were large within-subject and betwwn-subject differences. Nevertheless, in a number of instances there was a sharp increase in latency and misses at about the same time that irregularity made its appearance. Sometimes this would be seen on an individual day (fig. 2) at other times a relationship coul be shown only by grouping the data (fig. 3).

1

2

3

Hours

Fig. 2.

Response times 0x1 a single day with added ‘~‘vigilance”. A time of 10 set is a “miss”.

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IL F. H. MURRELL

Hours

-

Fig. 3. Above: percentage sf misses and below: percentage of response times longer than 4 szlc over 5 days with added “vigilance*’ (subject P)).

A telatimship between latency scores and skin conductance is by no means alwys easy ~toestablish. In some instances it appears to be nm-existent while in others a relationship does appear to exist. Fur in&me, in fig. 4 skin cmductance tended to fall after the first 3Wi

2

3

Hours

Pi& 4. Relationship between percentage of “vigilance” detections and skin conduchnce. Occurrence of missed detections are starred (subj!ect0 on 14/3/M).

3uur to reach aclow after 1% hours. In the same way, the number of dete&cms fell from mmplete success to 100 % misses. Just before 2 hours a cup of coffee was taken without stopping work and this was

AuTO-AROuSAL IN MONOTONOUS

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TASKS

followed by a rise in conductance and an improvement in vigilance ere was again a 1 e other hand, fig. 5 s

Coffee

2

1

here

3

Hours

Relationship conductance.

between percentage of “vigilance” de,tections and There were no “miss~:s” (subject 0 on 7/3/66).

skin

that there was very rapid detection while conductance was. rising, but slowed down when cunductance was high. The only really slow response (7.4 set) did however coincide with a “low” in conduSctance (there were no “misses” at all on this day) and there was some improvement in conductance and ti latency after coffee had been taken. These results indicate that where two different methods of detecting lthe onset of chanp of performance are used, they may show a relationship which suggests they have a Tmmmon cau.se. One or both cufthem may be related Ito changes in skin conductance. We have not, as ye$ fully investigated the relationship between these measures and output. EVIDENCEONAUTO-AROUSAL

When a period cf work commences there is usually a warm-up which shows as an increase in the rate of work, and a reductim in variabiity. This is generally accompanied by an increase in skin

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conductance. When 2 Ss are tested together the skin conductance tends to remain high for a period and to be rather variable, possibly due to varying interaction between Ss. When subjects are isolated and remain incommunicado for the whole of the experimental session of 3l/ hours the skin conductance tends to fall ,throughout t e period on the first occasion under this condition, and is less variable than when Ss work in Ipairs. But as the Ss become more accustomed to isolation, tlze skin conductance p&tern fell less steeply and more nearly approached the general shape found when Ss work together: output also increased. In one subject when at the outset there was a steep fall in conductance, output was 1890 and this increased over 4 isolation sessrons to 2075, when skin conductance fell much less. Since experimental conditions have not altered in any way, this improvement must have emanated from within the subjeot herself, so that she was progressively able to compensate for the extremely monotonous condition ,in.towhich she had been placed,. When a subject was put into isolation but with vigilance added skin conductance did not fall steeply as it did when vigilance WLTabsent; in some instances it remained substantially level and productile was high. This suggests that the vigilance task is a source of additional arousal which has a similar effect to the auto-a! L dsal which was necessary without vigilance. In one instaree the arousal is clearly external but i__ the other it can only have come from within the subject herself, Experiments were also carried out using various drugs. When a small dose of alcohol (23.7 ml of whiskey containing 40 % alcohol) was given the skin conductance level remained high for a period of more than an hour, and output was very high indeed. But with larger doses of ‘double and quadruple this size, there was an immediate fall in skin conductance followed, sometimes, by an increase when the effects of the alcohol had worn off; output was very low. When the Ss were given a cup of coffee, which contained 1.4 mg of caffeine, ingestion was followed by an increase both in skin conductance and in output. But when 2.5 mg and 5.0 mg were given in ,capsule form alternately with a placebo there was no obvious effect, except on one day with the 2.5 rag dose. A sinrilar effect was observed when 5.0 mg of dextroampheta~mine-sulphate was administered in capsule form as an alternative to a placebo. With most Ss there was no very marked effect, except for a tendency for skin conductance to inaease (figs 6a). 0ne subject was different; she had come to believe th& the placebo was the amphetamine and there was a marked change

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Amphetamine 4

(b)

I 2

1

Placebo

3/5/6i

3

Houzs

Fig. 6. Skin conductance on three days in the experiment (subjeci

with amphetamine

S:.

in her skin conductance at the time ac which she thought the capsule WC&I take effect after the j.placebo had been administered (fig. 6b and c). She also indicated that when she expected the amphetamine to boost her output she did nat need to make mu& effort herself. This is perhaps reflected in the sharp drop in her conductance before the placebo had “taken effect” It was she also, who showed the marked increase in skin conductanr e after taking the 2.5 mg dose of caffeine, and it transpired afterwar& that she again had come to the lvrong conclusion that she had betin given the 5.0 mg dose. In general, the Ss in this experiment seem to have performed in a manner determined by their beliefs in the results which would ensue: thy knew that a cup of coffee was suppose.d to be a stimulant but. did not know which of the pills contained what, so the pills hnd little or no effect, except when one S had wrongly made up her mind about their contents. As a result, her performance was influenced in the manner she expected, even though the effects should not have occurred in the way they did, This would explain the anomolous

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result with the small doses of alcohol. Alcohol is a cerebral depressant but the popular belief is that it acts as a stimulant, ad it would seem that a small dose is not sudEciently depressing to overcome ;the stimulating effect of tl&5 belief. Or Ito put it another way, the belief that alcohol is a stimdaxd could lead to s&Cent auto-arousal to overcome the deprasent effect of small doss, but not, of course, be su&ient to munteract large doses. Since in these experiments &here were no external determinants of change the anomolous rises in skin conductance and in petiormance must have been predicated by the Ss themselves; if they knew (or thought they knew) what they were getting their performance was appropriately iufluenced. This may, itherefore, be taken as evidence for the mechanism of autearousal. The effects so far described have been seen most clearly in the skin conductance curves. If the skin conductance b a measure of arousal, the behavioural measurements have not, by any means, always followed prediction. One of the difficulties of this kind of work is that from the results obtained it would be possible to pr+llce some which would show that nothing whatsoever has happer&; equally as has been de:tibed above, results have been obtained which do support the views put forward. That this should be the case need not necessarily disprove the general thesis. It is not part of the proposition that autoarousal will laZways occur in a given set of conditions. The very fact that the effects looked for occur only in some of the experiments is further evidence that we have been dealing with an arousal effect which can be manipulated at the will of the subject and over which the experimenter may have only partial control - if, in fact, he has any control at all. CONCLUSION

From the foregoing, we can arrive at frrur tentative conclusions. (1) Auto-arousal is probable. and may be compared wilh “selfarousal” of FRENCH et al. (1955), or with “wa>kefulness of choice” of KLEITMAFI,.inthe 1939 sense, but not his 1963 revision. (2) That byper-arousal is improbable as a cause of appearance of irregularity. (3) The effects which have been sf.udied are too complex to describe by a single non-specific level of arousal (LACEY,1966).

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(4) The part played by the thalamic extension of the reticular formation which cm produce specific activation needs to be further investigated (LINDSLEY, 1960). At ,the outset of this paper I outlined theories which I presented in my earlier papers. In view of the material which hase come to hand since, these thmies are m longer tenable. As an alternative, I now put forward the following tentative proposal: auto-arousal can produce phasic as well as tonic arousal with the phasic arousal directed towards a particular objective. A phasic change may produce a shift in tonic level. It is well established tha$ there are “damping dolvn”, corticofugal projections to the reticular formation which must increase as autoarousal increases if homeostasis is to be maintained. It is suggested that it is these downward projections and not hyper-arousal which cause qtie irregularity (psychological “fatigue”?) and/or deterioration of performance. As the damping down increases, it will override other effects (if it did not, the organism would “blow-up”) and will continue until there is some change in status such as a break in the continuity of the task, or until a balance is reached when arousing effects can again predominate. In other words, some of the behavioural effects which have been described may be related to what may b,e called anti-uriwal.

When all this has been said, we must remember that a subject may manipulate her arou.sal as she wishes, and not as is wished by the experimenter.

ACKNOWLEDGEMENTS

The work describd in this paper was carried out under a grant from the Science Research Council. The experiments were run by Miss Niru Bhatia, assisted by the Misses Diana Howcroft and Lorna Haines; their help is gratefully acknowledged.

REFERENCES BAKERC. H., 1959. Toward a theory of vigilance. Canad. J. Ps~chol. 13, 35-42. BARTLETT,F. C., 1953. Psy&olc&a.l critetia of fatigue. In: W. F. Flbly~3and A. T. Welford (eds.), Symposium an Fatigue. London: H. K. Lewis. BEROIJM,B., 1966. .A taxonomic analysis of continuous performance. Percept. Mot. 9kius 23, 47-54.

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BROADBENT, D. E. and M. Gltm;l~y,

1963. Vigilance considered as a statistical decision. Brit. J. Psyc:‘holl.54, 309-323. FRENC;W, J. D., R. B. LIVINGSTCN~ and R. HERN~DESP~ON, 1955. Projections from cortex to cephatitr braiu stem (reticular formatior ) in monkey. J. Neurophysid. 18, 74-95. HAGER, M., 1963. BxperimenteRe Untersuchungen iiber Daueraufmerksamkeit und cerebrale Vigilauz bei eintoermigen Taetigkeiten. 2. exp. angew. Psychoi. 10, l-18. HOLLAND,J. G., 1958. Human vigilance. Science, 128, 61, 67. JEIUWN,J., 1%7. Activation and long term perfor,mance. In: A. F. Sanders (ed.), Attention and performance. Amsterdam: North-Holland Pub. Co. KLE~~?MAN, N., 1939. Sleep and wakefulness. Chicago: Univ. of Chicago Press. -3 1963. Sleep and wakefulness, 2nd edition. Chicago: &iv. of Chicago &ss, p. 366. LACEY,J. I.,, 1966. Somatic response po~ttterning and stress: some revisions of activation theory. In: M. H. Appley and R. Trumbull (eds.), Psychological stress: issues in research. New York: Appleton-Century-Crofts. LIMSLEY, D. B., 1960. Attention, co~sciousnness, sleep and wakefulness. In: 3. Field, H. W. Magoun, and V. E. Hall (eds.), Handbook of Physiology, Vol. 3, Wmhington: American Physiological Society. URRELZ,M. F. H., 1.962. Gperator variability and its industrial consequences. Int. 1. Prod. Res. l(3) 39--:55. , 1965. Le concept de fatigue une r&alit& ou une g&e. Bull. C.E.R.P. 14, 103-l 10. , 1966. Performance decrement - a tentative explanation. In: F. F. Leopo1.d (ed.), Proc. 2nd Seminar on Continuous Work. Eindhtiven: Institute for Perception Research, 122-126. -- -, 1967. Performance di?Ferences in continuous tasks. In: A. F. Sanders (ea.), .Atteution and performance. Amsterdam: North-Holland. Pub. co. and B. FORSAITH, 1963. Laboratory studies of repetitive work. II: Resuhs from two subjects. Int. J. Prod. Res. 2, 247-264.