A term referring to a variety of mental capabilities, including the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience.

Throughout the 20th century scientists have debated the nature of intelligence, including its heritability and whether (and to what extent) it exists or is measurable. The 1994 publication of Richard J. Herrnstein and Charles Murray's volume The Bell Curve brought these debates to the forefront of public attention by discussing links between social class, race, and IQ scores, despite the fact that many have questioned the validity of IQ tests as a measurement of intelligence or a predictor of achievement and success.

Although the assessment of mental abilities through standardized testing has had many detractors, especially over the past 30 years, the notion that intellect is a measurable entity—also called the psychometric approach—lies at the heart of much modern theorizing...