Who is the Best Person for the Job?
Psychological tests and assessments have been used in personnel selection since World War I, but until the 1980s, it was assumed that the determinants of success varied extensively from job to job, and from organization to organization. In particular, it was widely believed that tests that were highly effective predictors of success in one job or one organization might turn out to be useless as predictors of success in other similar jobs or organizations, and that it would be necessary to build selection tests one job and one organization at a time. Several decades of research by psychologists Frank Schmidt, PhD, and John Hunter, PhD, showed that this assumption was incorrect, and that it was possible to establish clear, simple, and generalizable links between broad individual difference variables, such as general cognitive ability or personality traits and success in a wide range of jobs.
Two broad individual difference variables, general cognitive ability and conscientiousness, appear to be relevant to performance in virtually every job studied. Measuring these two variables alone, it is often possible to account for 20-30% of the variance in job performance, with even higher predictability in more complex jobs. It is often possible to improve prediction somewhat by adding job-specific predictors, but the most important predictors of performance are often the most universal (psychologist Malcolm Ree and colleagues suggest that the influence of general cognitive abilities is so broad and so strong that there is little to be gained by studying specific abilities that would seem relevant on the basis of an examination of job content). As a result of this research, our understanding of how individual differences influence job performance has moved from a model in which every job and every organization was thought to be unique (meaning that whatever you learned from studying performance in one job would have little relevance to understanding performance in other jobs) towards a model in which broad theoretical statements about the relationships between characteristics of people and characteristics of jobs interacting can be proposed and tested.
For example, Schmidt and Hunter's research suggests that general cognitive ability influences job performance largely through its role in the acquisition and use of information about how to do one's job. Individuals with higher levels of cognitive ability acquire new information more easily and more quickly, and are able to use that information more effectively. Drawing from this literature, psychologist Kevin Murphy, PhD, suggested that cognitive ability should be more important in complex jobs, when individuals are new to the job, and when there are changes in the workplace that require workers to learn new ways of performing their jobs. All of these predictions have been tested and supported.
Research linking broad concepts such as cognitive ability and conscientiousness to performance in a wide range of jobs has transformed the practice of personnel selection. At one time, personnel selection seemed to require custom test development for every new job, organization, etc., and it often appeared that these tests did a relatively poor job predicting job performance. Psychological research has lead to better approaches to selection that provide an excellent starting point for predicting future success (applicants who are high on cognitive ability and conscientiousness are likely to be relatively successful in a wide array of jobs).
Cognitive ability tests are widely used in both military and civilian sectors, but their use is often controversial because of ethnic group differences in ability tests scores. Personality inventories typically do not show these ethnic group differences, and the combination of cognitive tests and measures of broad personality factors can serve to both increase the validity of selection decisions and reduce, somewhat, the group differences in selection outcomes that would be produced using cognitive tests alone.
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American Psychological Association, May 20, 2004