Conceptual foundations of IQ testing

Cognitive neuroscience has not yet arrived at a definition of what human "i ntelligence" is. Intelligence is a chapter-heading word used in the 19th ce ntury to denote some unspecified mental property that increases in evolutio n. Other words were given speculative evolutionary meanings in the 19th cen tury: genius, degeneracy, retardation. When the Binet-Simon test came along as a test to screen degrees of mental retardation, later as a pupil classi fication instrument, some (not Binet) associated the test with these 19th-c entury words and meanings. Descendants of the Binet-Simon instrument, IQ te sts, remain useful today, but the old legendry lives on with them, at times supporting speculative social and political arguments. Researchers need to disentangle what is factual about IQ testing from its associated legendry.