Psychological testing, IQ, and evolutionary fitness.

Individual group, and ethnic differences in behavior have been an object of long, continuing, and contentious interest, both in the sciences and in popular culture. For well over 2,000 years, psychological traits, particularly those described as 'intelligence', have generally been considered the major factors in fitness in humans. After reviewing contemporary scientific thinking on intelligence, the psychometric methods used for the construction of psychological tests are presented and examined in the context of natural selection and metric characters. There are essential differences between the disciplines of genetics and of psychology such that the concepts of the two are more divergent than might superficially appear to be the case. The analysis leads to the conclusion that standard psychometric methodology cannot yield tests appropriate for measurement of evolutionary fitness characters.