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Man in the Control Room
LEADING ARTICLES
THE LANCET LONDON
4
JUNE
1966
Man in the Control Room As automation extends in industry, jobs which consist of monitoring automatic equipment are becoming more common. This type of work raises special difficulties for the operator, and four interrelated problems can be recognised-isolation, boredom, variability in work-load, and the need for vigilance.’ Isolation may seem to be an inevitable consequence of automation, for automatic processes need fewer men to control them. But men working alone tend to be less vigilant than those working in pairs or small groups, and making decisions appears to be easier when there is company, even though the decisions themselves are not discussed with companions. WELFORD,2studying the question of boredom, suggested that there are four critical speeds of signal presentation: (1) a very fast rate, at which the operator shows sign of strain; (2) a slower rate, at which strain is absent and the operator’s interest is well maintained; (3) a still slower rate which makes the operator bored and unwilling to do the task; and (4) a very slow rate, tolerable because the operator spends most of his time doing something else (such as reading a book or talking to his neighbours). Many automatic processes put the operator into the third category: there may be whole shifts without any alarms, but he cannot relax in case something happens. He becomes bored and resents emergencies when they do arise. He may also be inefficient because of lack of practice in handling the unusual events and because boredom breeds loss of interest and initiative. Making him record instrument readings at intervals does not help, for he realises that it is an artificial task that could probably be done more accurately by the machine. Giving him two monitoring tasks is no solution : while his attention is divided, if anything goes wrong with one he is more likely to miss a developing fault in the other. Variability in work-load is the most stressful aspect of control-room supervision. The operator may have nothing to do for long spells, but he has to react quickly in an emergency; and if automatic alarms are not built into the equipment he may also have to recognise when an emergency is developing. He may then have to take over complete manual control of a process which, before automation, was supervised by several operators. This may entail making rapid and responsible decisions to which he is unaccustomed. When he is overloaded in this way he may misread information or make the wrong deduction from the data. Loss of vigilance may be troublesome because equipment designers flatter the 1. 2.
Raffle, P. A. B. Trans. Ass. ind. med. Offrs, 1965, 15, Welford, A. T. Br. J. ind. Med. 1958, 15, 99.
88.
1251
capabilities of the human monitor. They seem unaware of the difficulties of remaining watchful when there is very little going on. Camera studies have shown that the operator may easily miss some important abnormal signals in a mass of normal signals, even though he is looking directly at the display. PoULTON3 has discussed some of the underlying psychological processes of the patternrecognition tasks involved in deciding whether a plant is functioning adequately or not. The modern view is derived from statistical decision theory.4 POULTON showed that the operator has to decide what are and what are not acceptable readings of the instruments. He sets himself a criterion, and if the readings are below this the situation is correct; if above, there is a fault. Whatever criterion is chosen, some correct situations will be thought to be faults. The operator can classify most of the faults without including a large proportion of false alarms, but in order to catch almost all of them he will classify some correct situations as faults. The practical importance is that if the operator is discouraged from giving false alarms, some abnormal situations will also not be reported. Reduced vigilance at the end of a shift is due to a change in the operator’s self-imposed criteria (he is less sure of himself) and not to a reduction in the number of signals perceived.’ Vigilance capacity varies, but BAKER and WARE6 found that individual performance on vigilance tasks cannot be predicted from performance on other routine tasks like inspection, assembly, and addition. Usually the fundamental decision in designing automatic equipment is to determine which part of the control function is best done by the machine and which by man. Often it is discovered that much of the monitoring task can be transferred to the machine. This reduces vigilance problems and may put the operator into WELFORD’S fourth category-to be brought into the control function only when an alarm rings. The work-load of absorbing a great deal of data and making quick decisions could be reduced by laying out the indicators in the sequence in which the information is needed and combining information from several sources in one indication. The task would be eased by laying out the controls in the same sequence as the indicators, and movement of a control should make the corresponding indicator move in the same direction. (How long, for instance, will clockwise rotation be needed for decreasing the flow of fluids or gases and anti-clockwise movement for reducing electricity supply?) It should also be possible for the operator to take a decision and promptly take the appropriate action, which the equipment may not carry out until later, but then without further intervention. Thus the operator does not have to remember to take action later; he is free to concentrate on the developing situation and to correlate unexpected observations that cannot yet be programmed into automatic equipment. If abnormal operation of the equipment is rare, the operator may have to be trained to deal with emergencies on 3. 4. 5. 6.
dummy machines. E. C. Trans. Ass ind. med. Offrs, 1965, 15, 96. Swets, J. A., Tanner, W. P., Birdsall, T G. Psychol. Rev. 1961, 68, Broadbent, D. E., Gregory, M. Br. J. Psychol. 1963, 54, 309. Baker, R. A., Ware, J. R. Ergonomics, 1966, 9, 109.
Poulton,
301.
1252
If further automation is not feasible, the best course may be to make the operator control more rather than less of the process. He will know what is going on all the time, and his work-load will vary less. Decision-making will be easier, because when an emergency does arise he has all the information at his fingertips. He may also move from WELFORD’S third to second category. The logical layout of indicators and controls is as important in this situation as it is with increased automation. The information displays should give all the information required, but only this; and in the correct order, at the time it is needed, and in the form most easily assimilated. The designers of automatic equipment are not getting all the help they need in the reduction of human problems. The hindrances are poor interdisciplinary communication, inadequate education of engineers in ergonomics, and failure of doctors to appreciate their patients’ difficulties at work.
Family Likeness IN 1887 FRANCIS GALTON devised a method of correlation for measuring resemblances between relatives; but it was not until 1900, when MENDEL’S paper on particu-
late inheritance was rediscovered, that a theoretical basis was found for his calculations, enabling geneticists -a new breed of scientists-to estimate values of correlations for single pairs of genes in hypothetical populations breeding at random. Soon, however, it became obvious that these simple assumptions were inadequate. In real life the situation is complicated by such things as multifactorial inheritance, incomplete dominance, multiple allelomorphism, and linkage, as well as assortative mating-the tendency for like to marry like. In 1918 R. A. FISHER, then only 28, analysed the effects of all these complications, and combinations of them, on the correlation between relatives. His paper was a great step forward in the understanding of genetics, but his exposition is at times difficult to follow. Dr. P. A. P. MORAN and Dr. C. A. B. SMITH have now reviewed the paper in detail, and FISHER’S original work has been republished/ with their discussion, explanations, and criticisms interjected as a running commentary. In the vast majority of characters human populations show continuous variation which, according to the tenets of mendelism, must be ascribed to the additive action of genes at several loci. In the inheritance of such characters, offspring show considerable variation of their parents’ measurement. Moreover, they show regression towards the mean of the general population: thus, sons of tall fathers tend to be tall, but not as tall as their fathers. FISHER estimated that, for height, perhaps a quarter of this variance is due to the genetic link between father and son, and another quarter to the link with the mother (assuming random about the
mean
1. Commentary on R. A. Fisher’s Paper on the Correlation between Relatives on the Supposition of Mendelian Inheritance. By P. A. P. MORAN and C. A. B. SMITH. Eugenics Laboratory Memoirs, XLI. London: Cambridge University Press. 1966. Pp. 62. 20s.
mating; rather less if, as usually happens, the heights of the parents are positively correlated). About 54% of the variance is attributable to the " total effect of ancestry ", leaving 46% to be explained by some other means. FISHER went on to show that most of the remaining variability is also due to the parents, being caused by their heterozygosity. The environmental contribution may be very small. In elementary genetics a useful maxim is: heredity provides the plans and blueprint; environment the bricks and mortar ". In practice, it seems that environment often adds little more than the final lick of paint. This is borne out by studies on monozygotic twins. In SHIELDS’ survey2 of identical twins brought up together and apart, the results were much as FISHER predicted: the twins remained very similar in various characters (such as height, intelligence, and personality measurements) despite differences in environment during childhood. Pairs of relatives inevitably " share " some of their A boy inherits half his father’s genes, and a genes. and uncle have a 50% probability of sharing a nephew given gene (sharing by descent, that is; very common genes will often be acquired from various sources). But when it comes to one’s great-great-grandfather’s second cousin the chances of having a certain gene in common is only 1 in 1024. A glance at FISHER’S cold statistical analysis would remove the glamour surrounding a claim to descent from some swashbuckling 17thcentury pirate. The attraction of family-trees is, of course, that they can be selective; but would the American ladies who can count King John’s barons among their ancestors have been so eager to pay their respects at Runnymede had they realised that they probably had over 40,000 forebears in the knights’ "
generation ? In the 1918 paper we see the beginning of some of FISHER’S most important evolutionary ideas. He was aware that the heterozygote differs somatically from the mean of the dominant and recessive phases, although genetically it is intermediate, and he took account of this dominance deviation in his calculations of family correlations. Presumably this was the germination of his hypothesis that the evolution of dominance is effected by selection operating on the total gene-complex,3 the expression of a gene being modified by different genic environments. MORAN and SMITH’S assessment is especially useful in the treatment of the few defects of FISHER’S paper. FiSHER’s analysis of linkage (" coupling " was his term for this) dealt only with completely linked and completely unlinked genes; and although his conclusionthat " coupling is without influence on the statistical properties of the population "-is confirmed, his reasoning is shown to be faulty. When linkage is complete the gene combination can be regarded as a single factor, segregation resulting in free assortment, as for independent genes. In partial linkage the recombination frequencies are determined by the properties of the system, and its effect on family correlations 2. Shields, J. Monozygotic Twins. London, 1962. 3. Fisher, R. A. Am. Nat. 1928, 62, 115; ibid. p. 571.
THE LANCET LONDON
4
JUNE
1966
Man in the Control Room As automation extends in industry, jobs which consist of monitoring automatic equipment are becoming more common. This type of work raises special difficulties for the operator, and four interrelated problems can be recognised-isolation, boredom, variability in work-load, and the need for vigilance.’ Isolation may seem to be an inevitable consequence of automation, for automatic processes need fewer men to control them. But men working alone tend to be less vigilant than those working in pairs or small groups, and making decisions appears to be easier when there is company, even though the decisions themselves are not discussed with companions. WELFORD,2studying the question of boredom, suggested that there are four critical speeds of signal presentation: (1) a very fast rate, at which the operator shows sign of strain; (2) a slower rate, at which strain is absent and the operator’s interest is well maintained; (3) a still slower rate which makes the operator bored and unwilling to do the task; and (4) a very slow rate, tolerable because the operator spends most of his time doing something else (such as reading a book or talking to his neighbours). Many automatic processes put the operator into the third category: there may be whole shifts without any alarms, but he cannot relax in case something happens. He becomes bored and resents emergencies when they do arise. He may also be inefficient because of lack of practice in handling the unusual events and because boredom breeds loss of interest and initiative. Making him record instrument readings at intervals does not help, for he realises that it is an artificial task that could probably be done more accurately by the machine. Giving him two monitoring tasks is no solution : while his attention is divided, if anything goes wrong with one he is more likely to miss a developing fault in the other. Variability in work-load is the most stressful aspect of control-room supervision. The operator may have nothing to do for long spells, but he has to react quickly in an emergency; and if automatic alarms are not built into the equipment he may also have to recognise when an emergency is developing. He may then have to take over complete manual control of a process which, before automation, was supervised by several operators. This may entail making rapid and responsible decisions to which he is unaccustomed. When he is overloaded in this way he may misread information or make the wrong deduction from the data. Loss of vigilance may be troublesome because equipment designers flatter the 1. 2.
Raffle, P. A. B. Trans. Ass. ind. med. Offrs, 1965, 15, Welford, A. T. Br. J. ind. Med. 1958, 15, 99.
88.
1251
capabilities of the human monitor. They seem unaware of the difficulties of remaining watchful when there is very little going on. Camera studies have shown that the operator may easily miss some important abnormal signals in a mass of normal signals, even though he is looking directly at the display. PoULTON3 has discussed some of the underlying psychological processes of the patternrecognition tasks involved in deciding whether a plant is functioning adequately or not. The modern view is derived from statistical decision theory.4 POULTON showed that the operator has to decide what are and what are not acceptable readings of the instruments. He sets himself a criterion, and if the readings are below this the situation is correct; if above, there is a fault. Whatever criterion is chosen, some correct situations will be thought to be faults. The operator can classify most of the faults without including a large proportion of false alarms, but in order to catch almost all of them he will classify some correct situations as faults. The practical importance is that if the operator is discouraged from giving false alarms, some abnormal situations will also not be reported. Reduced vigilance at the end of a shift is due to a change in the operator’s self-imposed criteria (he is less sure of himself) and not to a reduction in the number of signals perceived.’ Vigilance capacity varies, but BAKER and WARE6 found that individual performance on vigilance tasks cannot be predicted from performance on other routine tasks like inspection, assembly, and addition. Usually the fundamental decision in designing automatic equipment is to determine which part of the control function is best done by the machine and which by man. Often it is discovered that much of the monitoring task can be transferred to the machine. This reduces vigilance problems and may put the operator into WELFORD’S fourth category-to be brought into the control function only when an alarm rings. The work-load of absorbing a great deal of data and making quick decisions could be reduced by laying out the indicators in the sequence in which the information is needed and combining information from several sources in one indication. The task would be eased by laying out the controls in the same sequence as the indicators, and movement of a control should make the corresponding indicator move in the same direction. (How long, for instance, will clockwise rotation be needed for decreasing the flow of fluids or gases and anti-clockwise movement for reducing electricity supply?) It should also be possible for the operator to take a decision and promptly take the appropriate action, which the equipment may not carry out until later, but then without further intervention. Thus the operator does not have to remember to take action later; he is free to concentrate on the developing situation and to correlate unexpected observations that cannot yet be programmed into automatic equipment. If abnormal operation of the equipment is rare, the operator may have to be trained to deal with emergencies on 3. 4. 5. 6.
dummy machines. E. C. Trans. Ass ind. med. Offrs, 1965, 15, 96. Swets, J. A., Tanner, W. P., Birdsall, T G. Psychol. Rev. 1961, 68, Broadbent, D. E., Gregory, M. Br. J. Psychol. 1963, 54, 309. Baker, R. A., Ware, J. R. Ergonomics, 1966, 9, 109.
Poulton,
301.
1252
If further automation is not feasible, the best course may be to make the operator control more rather than less of the process. He will know what is going on all the time, and his work-load will vary less. Decision-making will be easier, because when an emergency does arise he has all the information at his fingertips. He may also move from WELFORD’S third to second category. The logical layout of indicators and controls is as important in this situation as it is with increased automation. The information displays should give all the information required, but only this; and in the correct order, at the time it is needed, and in the form most easily assimilated. The designers of automatic equipment are not getting all the help they need in the reduction of human problems. The hindrances are poor interdisciplinary communication, inadequate education of engineers in ergonomics, and failure of doctors to appreciate their patients’ difficulties at work.
Family Likeness IN 1887 FRANCIS GALTON devised a method of correlation for measuring resemblances between relatives; but it was not until 1900, when MENDEL’S paper on particu-
late inheritance was rediscovered, that a theoretical basis was found for his calculations, enabling geneticists -a new breed of scientists-to estimate values of correlations for single pairs of genes in hypothetical populations breeding at random. Soon, however, it became obvious that these simple assumptions were inadequate. In real life the situation is complicated by such things as multifactorial inheritance, incomplete dominance, multiple allelomorphism, and linkage, as well as assortative mating-the tendency for like to marry like. In 1918 R. A. FISHER, then only 28, analysed the effects of all these complications, and combinations of them, on the correlation between relatives. His paper was a great step forward in the understanding of genetics, but his exposition is at times difficult to follow. Dr. P. A. P. MORAN and Dr. C. A. B. SMITH have now reviewed the paper in detail, and FISHER’S original work has been republished/ with their discussion, explanations, and criticisms interjected as a running commentary. In the vast majority of characters human populations show continuous variation which, according to the tenets of mendelism, must be ascribed to the additive action of genes at several loci. In the inheritance of such characters, offspring show considerable variation of their parents’ measurement. Moreover, they show regression towards the mean of the general population: thus, sons of tall fathers tend to be tall, but not as tall as their fathers. FISHER estimated that, for height, perhaps a quarter of this variance is due to the genetic link between father and son, and another quarter to the link with the mother (assuming random about the
mean
1. Commentary on R. A. Fisher’s Paper on the Correlation between Relatives on the Supposition of Mendelian Inheritance. By P. A. P. MORAN and C. A. B. SMITH. Eugenics Laboratory Memoirs, XLI. London: Cambridge University Press. 1966. Pp. 62. 20s.
mating; rather less if, as usually happens, the heights of the parents are positively correlated). About 54% of the variance is attributable to the " total effect of ancestry ", leaving 46% to be explained by some other means. FISHER went on to show that most of the remaining variability is also due to the parents, being caused by their heterozygosity. The environmental contribution may be very small. In elementary genetics a useful maxim is: heredity provides the plans and blueprint; environment the bricks and mortar ". In practice, it seems that environment often adds little more than the final lick of paint. This is borne out by studies on monozygotic twins. In SHIELDS’ survey2 of identical twins brought up together and apart, the results were much as FISHER predicted: the twins remained very similar in various characters (such as height, intelligence, and personality measurements) despite differences in environment during childhood. Pairs of relatives inevitably " share " some of their A boy inherits half his father’s genes, and a genes. and uncle have a 50% probability of sharing a nephew given gene (sharing by descent, that is; very common genes will often be acquired from various sources). But when it comes to one’s great-great-grandfather’s second cousin the chances of having a certain gene in common is only 1 in 1024. A glance at FISHER’S cold statistical analysis would remove the glamour surrounding a claim to descent from some swashbuckling 17thcentury pirate. The attraction of family-trees is, of course, that they can be selective; but would the American ladies who can count King John’s barons among their ancestors have been so eager to pay their respects at Runnymede had they realised that they probably had over 40,000 forebears in the knights’ "
generation ? In the 1918 paper we see the beginning of some of FISHER’S most important evolutionary ideas. He was aware that the heterozygote differs somatically from the mean of the dominant and recessive phases, although genetically it is intermediate, and he took account of this dominance deviation in his calculations of family correlations. Presumably this was the germination of his hypothesis that the evolution of dominance is effected by selection operating on the total gene-complex,3 the expression of a gene being modified by different genic environments. MORAN and SMITH’S assessment is especially useful in the treatment of the few defects of FISHER’S paper. FiSHER’s analysis of linkage (" coupling " was his term for this) dealt only with completely linked and completely unlinked genes; and although his conclusionthat " coupling is without influence on the statistical properties of the population "-is confirmed, his reasoning is shown to be faulty. When linkage is complete the gene combination can be regarded as a single factor, segregation resulting in free assortment, as for independent genes. In partial linkage the recombination frequencies are determined by the properties of the system, and its effect on family correlations 2. Shields, J. Monozygotic Twins. London, 1962. 3. Fisher, R. A. Am. Nat. 1928, 62, 115; ibid. p. 571.