ABSTRACT

Ability measures defined in terms of latent traits were first theoretically investigated systematically by F. M. Lord (1952). During the 30 years to date there has been an increasing literature in this field, much of it acknowledging his original and continuing contribution (Lord, 1980; Lord & Novick, 1968). In the same 30 years there has also been an interest in cognitive development and the need to have an appropriate ability measure with which to describe this development (see for example Bayley, 1955). More recently Nesselroade and Baltes (1979) and others have reviewed methods of analyzing longitudinal data from various points of view. It is surprising that none of these reviews emphasizes the use of ability measures in longitudinal studies and indeed two of the more recent studies (those reported by Hindley & Owen, 1979; McCall, Appelbaum & Hogarty, 1973) continue to use deviation, IQ measures.