Intelligence and ability

Ability and intelligence are related, and in some ways opposite, views of human mental ability. Whereas an Intelligence Quotient constucts intelligence as being a single measurable characteristic affecting all mental ability, aptitude breaks mental ability down into many different characteristics which are supposed to be more or less independent of each other. However, a casual analysis of any group of test scores will nearly always show them to be highly correlated. The U.S. Department of Labor's General Learning Ability, for instance, is determined by combining Verbal, Numerical and Spatial aptitude subtests. In a given person some may be relatively low and others relatively high. In the context of an ability test the "high" and "low" scores are usually not far apart, because of the fact that all ability test scores tend to be correlated. Aptitude is better applied intra-individually to determine what tasks a given individual is relatively more skilled at performing. Inter-individual aptitude differences are typically not very significant due to IQ differences. Of course this assumes individuals have not already been pre-screened for IQ though some other process such as SAT scores, GRE scores, finishing medical school, etc.