section_path: Definitions
section_name: Definitions
paragraph_text: Definitions
  
  The definition of intelligence is controversial, varying in what its abilities are and whether or not it is quantifiable.
  
  In 1994 the " Mainstream Science on Intelligence " was published, as an op-ed statement in the Wall Street Journal, as a response to controversy over the book The Bell Curve which proposed policy changes based on purported connections between race and intelligence. It was signed by fifty-two researchers, out of 131 total invited to sign, with 48 explicitly refusing to sign. The op-ed described intelligence thus:
  
  A very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings—"catching on", "making sense" of things, or "figuring out" what to do.
  
  From Intelligence: Knowns and Unknowns (1995), a report published by the Board of Scientific Affairs of the American Psychological Association, also in response to controversy over The Bell Curve:
  
  Individuals differ from one another in their ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought. Although these individual differences can be substantial, they are never entirely consistent: a given person's intellectual performance will vary on different occasions, in different domains, as judged by different criteria. Concepts of "intelligence" are attempts to clarify and organize this complex set of phenomena. Although considerable clarity has been achieved in some areas, no such conceptualization has yet answered all the important questions, and none commands universal assent. Indeed, when two dozen prominent theorists were recently asked to define intelligence, they gave two dozen, somewhat different, definitions.
  
  Besides those definitions, psychology and learning researchers also have suggested definitions of intelligence such as the following: