APA News Release
Date: September 15, 1995
Contact: Doug Fizel
Public Affairs Office
APA Task Force Examines the Knowns and Unknowns of Intelligence
Many Critical Questions About Intelligence Are Still Unanswered
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
- 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
- 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."
(Full text of task force report available from the APA Public Affairs Office.)
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