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APA Task Force Examines the Knowns and Unknowns of Intelligence

1996 Press Release

What is intelligence and can it be measured? These questions have fueled a continuing debate about whether intelligence is inherited, acquired, environmental, or a combination of these and other factors. In a field where so many issues are unresolved and so many questions unanswered, the confident tone that has characterized most of the debate on these topics is clearly out of place, according to a new report by the American Psychological Association (APA).

The report, entitled 'Intelligence: Knowns and Unknowns,' was written by APA's Task Force on Intelligence. The task force convened in January 1995 to prepare a dispassionate and authoritative report in response to the fall 1994 publication of Herrnstein and Murray's The Bell Curve. 'Their book sparked a new and vigorous round of debate about the meaning of intelligence test scores and the nature of intelligence itself, a debate in which little effort was made to distinguish scientific issues from political ones,' stated Ulric Neisser, PhD, chair of the task force.

Because there are many ways to be intelligent, there are also many conceptualizations of intelligence. Standardized intelligence test scores (IQs), which reflect a person's standing in relation to his or her generational peers, are based on tests that measure a number of different abilities. Psychometric testing, the use of standardized tests to assess specific abilities, has generated the most systematic research though many questions remain unanswered. According to the task force report:

  • Intelligence test scores partially predict individual differences in school achievement, such as grade point average and number of years of education that individuals complete. In this context, the skills measured are important. Nevertheless, population levels of school achievement are not determined solely or even primarily by intelligence or any other individual-difference variable. The fact that children in Japan and Taiwan learn much more math than their peers in America, for example, can be attributed primarily to differences in culture and schooling rather than in abilities measured by intelligence tests.

  • Test scores also correlate to some extent with measures of accomplishment outside of school, for example adult occupational status. This correlation is linked with school achievement because, in the United States today, high test scores and grades are prerequisites for entry into many careers and professions. However, a significant correlation between test scores and occupational status remains even when education and family background have been statistically controlled.

  • Differences in genetic endowment contribute substantially to individual differences in (psychometric) intelligence, but the pathway by which genes produce their effects is still unknown. The impact of genetic differences appears to increase with age, but it is not known why.

  • Environmental factors contribute substantially to the development of intelligence, but it is not clearly understood what those factors are or how they work. Attendance at school is certainly important, for example, but it is not known what aspects of schooling are critical.

  • The role of nutrition in intelligence remains obscure. Severe childhood malnutrition has clear negative effects, but the hypothesis that certain 'micro- nutrients' may affect intelligence in otherwise adequately-fed populations has not been convincingly demonstrated.

  • The differential between the mean intelligence test scores of Blacks and Whites does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socio-economic status. Explanations based on factors of caste and culture may be appropriate, but so far there is little direct empirical support for them. There is certainly no such support for a genetic interpretation. At this time, no one knows what is responsible for the differential.

  • It is widely agreed that standardized tests do not sample all forms of intelligence. Obvious examples include creativity, wisdom, practical sense, and social sensitivity, among others. Despite the importance of these abilities, very little is known about them, how they develop, what factors influence their development, and how they are related to more traditional measures.

  • Although there are no important sex differences in overall intelligence test scores, substantial differences do appear for specific abilities. Males typically score higher on visual-spatial and (beginning in middle childhood) mathematical skills; females excel on a number of verbal measures. Sex hormone levels are clearly related to some of these differences, but social factors presumably play a role as well.

The task force distinguishes sharply between scientific research and political rhetoric. 'The study of intelligence does not need politicized assertions and recriminations; it needs self-restraint, reflection, and a great deal more research.' According to the report, the questions that remain are socially as well as scientifically important and 'that there is no reason to think them unanswerable, but finding the answers will require a shared an sustained effort as well as the commitment of substantial scientific resources.'

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 132,000 researchers, educators, clinicians, consultants and students. Through its divisions in 49 subfields of psychology and affiliations with 58 state and territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

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