Research Needs for Human Factors (1983)

Many areas of research in human factors have concentrated on systems that fit the average person. In those studies, individual differences traditionally have been treated as little more than an error problem. Thus few data are available in many areas of human factors on the interaction of different systems with variables such as ability levels or age levels. Attempts to classify, describe, predict, and exploit individual and group differences extend to the beginnings of recorded history. Some of the earliest decipherable samples of writings include references to the physical and mental differences between men and women, serfs and noblemen, slaves and masters, and barbarians and civilized persons. It was not until the nineteenth century, however, that the study of individual and group differences assumed the systematic and rigorous qualities of scientific investigation. The attempts of Sir Francis Galton (1822–1911) to describe the nature of individual differences are the foundations of what is sometimes referred to as differential psychology.

Since Galton, investigations of individual and group differences carried out by psychologists, anthropologists, and sociologists number in the hundreds of thousands. There is a psychological journal, The Journal of Cross-Cultural Psychology, entirely devoted to studies of this kind. One of the most important applications of this work in psychology has been the development of a multi-million dollar testing industry. Psychologists have devised hundreds of tests of ability, achievement,

skills, knowledge, and personality (Buros, 1978) that are used routinely for classifying and selecting employees for thousands of jobs and occupations.^★

One of the most ambitious and thorough attempts to relate individual characteristics of workers to job requirements is the Dictionary of Occupational Titles (U.S. Department of Labor, 1977). This compendium gives profiles of the educational, aptitude, interest, physical, and temperament characteristics required of a worker to achieve average successful job performance in thousands of occupations. The military services have tried to do something similar on a more modest scale. In the preparation of personnel requirements data, the Air Force Design Handbook (Air Force Systems Command, 1969) specifies that tasks should be rated along six dimensions: ambient environment, equipment characteristics, mental demands, physical demands, hazard exposure, and task criticality. Figure 6–1 shows the three levels of mental demands that may be required of people by various duties and tasks.

Although it is seldom explicitly stated, the underlying rationale of most of these classifications is that the job or the occupation is a given, a fixed quantity. The aim of personnel selection is therefore to find persons who have the abilities, skills, and other characteristics required to perform particular jobs. From the standpoint of human factors, however, a job is not a fixed quantity but rather something that can be modified and designed to fit people with varying characteristics. Thus it becomes important to know in what ways people vary and by how much. In this area there are serious gaps in our knowledge. The most thorough translation of individual difference data into design requirements has been done in the field of anthropometry, which involves measurement of the human body. It is possible to write equipment design specifications so that the equipment will fit 90 percent, 95 percent, or any other proportion of a particular user population. The information necessary to write equally precise design specifications for other human dimensions and characteristics, however, is not available.

Attempts have been made to do that, but further research is needed on this complex problem. The Air

Force’s six task dimensions of ambient environment, equipment characteristics, physical demands, hazard exposure, and task criticality are a good initial effort (see Table 6–1), yet the Air Force Design Handbook acknowledges its limitations: “Because of the broad range of equipment characteristics, complete criteria are not presented here. The following are merely suggested guidelines” (Section DN4C3, p. 13). For example, the manual states that Code 1 equipment is “…complex but adequately designed for ease of use….” What the definition does not specify is ease of use for whom. Something that is easy for an astronaut to use may be completely beyond the capabilities of an individual with only an elementary school education. To state the problem explicitly, we do not know exactly how to design complex equipment so that it can be used with ease by people with average IQs, people with IQs as low as 80, people with fifth-grade reading abilities, or people for whom English is a second language.

Antidiscrimination legislation has focused attention on human factors issues related both to complying with legislative requirements and maintaining the productivity of a work force with greater diversity than in the past. As a result there is increased concern over the interaction of individual differences with programs such as job redesign and training as well as over organizational attitudes toward various populations (e.g., the elderly) that may constrain their performance.

As a result of the U.S. Civil Rights Act, federal guidelines have been developed concerning personnel decisions that affect protected classes, which include: American Indian or Alaskian natives, blacks not of Hispanic origin, Hispanics, and Asian or Pacific Islanders. In addition, federal legislation has made it illegal to discriminate on the basis of sex, age, or disability. Any personnel action resulting in adverse impact against any of these groups can result in litigation. In this context, personnel decisions are not limited to selection or promotion but rather refer to any personnel practice, such as job and workplace redesign, selection for training, and the use of training as a basis for promotion.

Legal actions resulting from charges of discrimination have stimulated research on the procedures necessary to assess the validity of these types of personnel practices; however, most of the emphasis has been on the establishment of procedures to validate selection tests (American Psychological Association, 1980). Similar concerns are being expressed about methodologies for evaluating training and job redesign (Bartlett, 1978). The research emphasis has been on establishing data bases, so that it is possible to design programs that do not have adverse impact.

As a consequence of antidiscrimination legislation as well as social and economic factors, people from special population groups are moving into occupations that were previously considered nontraditional for them. An example is women who are entering managerial and blue-collar jobs and the military services. The military services are also accepting more people (male and female) who have lower ability as measured by traditional academic aptitude measures. These changes in the composition of the work force and the armed services have revealed an important problem in addition to the human factors issues of designing jobs, equipment, and training to accommodate individual differences: It has only recently been recognized that organizational attitudes toward people entering nontraditional jobs may adversely affect productivity by hindering their performance and constraining occupational aspirations.

Sheridan’s (1975) description of the American Telephone and Telegraph Company’s experience in placing women in craft jobs illustrates the implications of human factors for sex and job performance. Despite rigorous recruiting and comprehensive training efforts, the women recruited into a particular job dropped from training at an average rate of 50 percent, and the women who completed training usually did not last a full year on the job. A task analysis of the job indicated that the physical tasks were extremely difficult for women to perform; furthermore, this analysis determined which tasks were causing the most difficulty. Some of the most serious problems centered on the use of a ladder that weighed approximately 80 1bs. and was 14 feet long before being extended. Women had great difficulty placing the ladder against a building

because they had to apply force below the midpoint of the ladder just as the force required to raise it was increasing. A fiberglass tube was connected to the top rungs of the ladder that enabled the worker to push the ladder against the building much more easily. As a result, workers who were 5 foot 2 inches weighing 120 pounds were able to raise a 72 1b. ladder with one hand. These and other design modifications not only allowed women to perform the job but also resulted in fewer back injuries for men.

Important considerations with regard to age and job performance are that the average age of the population is increasing and both age discrimination legislation and rulings against forced retirement are resulting in a larger number of older people in the work force. Many of these individuals will require additional training as a result of job shifts, technological changes, or simply interest in a new career. The biases operating against these people are made obvious by Britton and Thomas’s (1973) study of the views of employment interviewers. They noted that 50-year-old workers were viewed as the most difficult to place during a recession, the most difficult for an employer to train, and the least able to maintain production schedules. These views are based on preconceived beliefs that older workers cannot perform as well on the job and cannot easily acquire new skills. Data relevant to these questions are virtually nonexistent; a thorough review (Fozard and Popkin, 1978) of perceptual and cognitive data analyzed by age reinforces the view that there are few data relevant to work situations. Much of that review is based on data from laboratory experiments on topics such as paired associate learning, iconic memory, and visual discrimination, making generalizations to work situations hazardous at best.

The deficient state of this research is summarized in Sheppard’s (1970) generalizations about basic research on aging and job performance: The research fails to differentiate various aspects of the work situation, including physical, psychomotor, sensory, and social characteristics; most of the emphasis is on average performance, with little, if any, attention to the substantial number of individual differences; and, there is a blind faith in

trend extrapolations. If workers ages 30–40 have lower morale than workers ages 20–30, it is simply assumed that workers ages 40–50 will have even lower morale.

A good example of the implications of our lack of knowledge is evidenced by the continuing controversy concerning airline pilot age, health, and performance. An Institute of Medicine (1981) report notes that although the average risk of acute incapacitation increases with age, there are large individual differences. In addition, while there are decreases in capacity, speed or accuracy of attention, memory, and intellectual skills with increasing age, there is also evidence that well-practiced skills may not show any age-related decline. The report concludes that there is a need for research on age-related changes among pilots and a need for research on pilot performance on tasks that are representative of actual work situations.

Of more immediate relevance to this report are the relationships between group variables such as age and equipment design. For example, as they age, many people require the use of bifocals. How does the use of bifocals relate to the need to read information from displays such as those found on word processing equipment? Is it possible that the displays must be designed differently or that the information must be displayed differently depending on the age of the operator? Questions such as these constitute a largely unexplored topic for research.

Another serious gap in our knowledge is how various individual and group differences interact to affect job performance. For example, there are considerable data available relating aging to maximum oxygen uptake, which determines the capacity of an individual to do prolonged heavy work (Astrand and Rodahl, 1977). These data show that there is a steady decrement in aerobic power beginning at about age 20, such that a 60-year-old attains about 70 percent of the maximum of a 25-year-old. Unfortunately, there are a few data on most population differences or individual differences as they are related to work situations. McFarland and O’Doherty (1959) concluded the following regarding the relationship of aging and work performance (pp. 454–455):

These and other interactions of variables are another almost completely untapped area of research.

There are, of course, other important differences in population characteristics that should be considered in job redesign and training systems. National and ethnic differences have implications for equipment design that have just recently begun to be investigated (Chapanis, 1975). These differences are reflected in anthropometric, physiological, psychological, language, and cultural variables that affect equipment design.

For example, Ruffell-Smith (1975) notes that telegraph systems were originally used as communication devices in air traffic control systems; however, with the increased amount of speed of air traffic, voice communication systems replaced telegraph devices. Obviously, the use of the different languages of the many nations involved in air travel was a serious impediment to the operation of voice systems. After World War II English was chosen as the language of use because at that time most aircraft were operated by English-speaking countries. Yet there is a wide variation in English dialects and pronunciation, to the extent that some dialects, such as that spoken in Newcastle, are not understood by people elsewhere in the British Isles. Obviously the problems are more severe when the speaker’s native language is not English. Ruffell-Smith’s analysis of communication errors indicates that this problem can be serious in air traffic communication, especially when the speed of reaction is a critical element in avoiding an accident. Clearly, the implications of these population differences should be considered in design decisions.

Ethnic Variables in Human Factors Engineering (Chapanis, 1975) provides other examples of equipment

design complexities caused by language differences. One chapter (Hanes, 1975) shows the variety of accounting keyboards that have been designed to accommodate some of the European and Mideast languages. Another chapter (Brown, 1975) illustrates the design problems that were encountered in designing a computer terminal for Japanese, a language that is markedly different from the Indo-European languages. In general, there is little appreciation of the problems involved in designing equipment for diverse national and ethnic groups. The Human Engineering Guide to Equipment Design (Van Cott and Kinkade, 1972) is the best single source of human factors data available, yet it is almost entirely concerned with American and European data. It is necessary to learn to what extent its data and design recommendations need to be modified or supplemented for international use.

Closely related to problems of equipment design are those associated with the training of individuals to operate complex equipment. Here again our information is seriously deficient. An approach that has some promise is the aptitude-treatment interaction (ATI) model. The goal of this approach is to match a particular mode of instruction to an individual’s distinctive characteristics so that each person is assigned the most appropriate learning procedure. A disordinal aptitude-treatment interaction is one in which individuals with high aptitude perform best with one treatment (e.g., training or display), while those with lower aptitude perform best with another treatment. Thus, the aptitude level of the individual determines the form of treatment that has the best chance of success. Aptitude in this context refers to any personal characteristics that relate to learning and so can include a broad range of variables, such as styles of thought, personality, and various scholastic aptitudes. Treatment has typically referred to instructional modes like programmed instruction, computer-assisted instruction, visual versus verbal presentations, etc; it can be generalized, however, to any intervention, including job redesign.

An exhaustive review of this appealing strategy is provided in the text by Cronbach and Snow (1977). They examined a large number of potential aptitudes, such as learning rates, abilities, and personality, and considered

their interactions with various instructional techniques. While early reviews of this topic were more pessimistic, Cronbach and Snow’s extensive review and reanalyses of data have led them to conclude that aptitude treatment interaction effects are real phenomena. They note that the findings that most clearly suggest ATI effects are those dependent on prior learning experience: The technique that works best is the one that an individual has already experienced. However, ATI effects have not often been generalized or replicated. Goldstein (1980) notes the need for systematic empirical and theoretical research that matches individual differences among learners to various instructional strategies. The haphazard assignment of individuals with particular abilities to any available instructional technique is not likely to produce dividends.

Another important topic is the identification of barriers to successful performance for different groups. For example, some employment interviewers perceive women as more likely to be absent and to have fewer skills, even though they have no evidence to support these beliefs (Britton and Thomas, 1973). Similarly, the elderly are viewed as difficult to train (Britton and Thomas, 1973). Researchers concerned with these issues emphasize that the identification of organizational constraints, in military organizations for example, is a first step in understanding and resolving their serious retention problem. One study (Boyd et al., 1975) of 1,573 women in their first tour in the Army’s basic training program was critical of the program’s failure to provide realistic expectations about the training process. Subsequent to the basic training program supervisors reported the main difference between good and poor performers was job-related attitudes (discipline, following orders, military courtesy) that were not adequately presented in basic training.

A research program to explore issues concerning population group and individual differences would need to take several approaches:

1. It is necessary to conduct literature reviews and examinations of reports that forecast which type of population group variables (such as age and sex) and which type of work situation parameters (such as visual displays on a word processor) will be important in the future.

2. It is necessary to collect and examine available theories and empirical data about the relevant parameters (e.g., changes in information processing capability as a function of age).

3. Research should be sponsored on a number of topics:

   • The relationship between population group variables and performance on relevant work tasks.

   • The interaction between population group differences and various interventions, such as job redesign and training.

   • The specification of design changes based on research findings resulting from these research recommendations.

4. In addition, data should be collected and analyzed to identify and remove organizational constraints that serve as barriers to the successful performance of various population groups, such as women and aged and handicapped people.

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Astrand, P.O., and Rodahl, K. 1977 Textbook of Work Physiology. New York: McGraw Hill.

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Brown, C.R. 1975 Human factors problems in the design and evaluation of key-entry devices for the Japanese language. In A.Chapanis, ed., Ethnic Variables in Human Factors Engineering. Baltimore, Md.: Johns Hopkins University Press.

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Goldstein, I.L. 1980 Training in work organizations. Annual Review of Psychology 22:565–602.

Hanes, L.F. 1975 Human factors in international keyboard arrangement. In A.Chapanis, ed., Ethnic Variables in Human Factors Engineering. Baltimore, Md.: Johns Hopkins University Press.

Institute of Medicine, National Academy of Sciences 1981 Airline Pilot Age, Health and Performance. Washington, D.C.: National Academy Press.

McFarland, R.A., and O’Doherty, B.M. 1959 Work and occupational skill. In J.E.Birren, ed., Handbook of Aging and the Individual. Chicago: University of Chicago Press.

Ruffell-Smith, H.P. 1975 Some problems of voice communication for international aviation. In A.Chapanis, ed., Ethnic Variables in Human Factors Engineering. Baltimore, Md.: Johns Hopkins University Press.

Sheppard, H.L. 1970 On age discrimination. In H.L.Sheppard, ed., Towards an Industrial Gerontology. Cambridge, Mass.: Schenkman.

Sheridan, J.A. 1975 Designing the Work Environment. Paper presented at the American Psychological Association, Chicago.

U. S. Department of Labor 1965 Dictionary of Occupational Titles. Fourth edition. Washington, D.C.: U.S. Department of Labor.

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