Fluid and Crystallized Intelligence

Introduction

Further Developments

Several models of intelligence integrate aspects of gf and gc. Gustafsson (1984) proposed a model including gf and gc as second-order factors, where gf was identical to general intelligence. Ackerman (1996) presented an integrative theory of adult intellectual development, focusing on intelligence-as-process representing gf-type abilities, and intelligence-as-knowledge representing gc-type abilities. Baltes et al. (1998) integrated gf and gc in the developmental concept of the mechanics (close to gf) and pragmatics (close to gc) of intelligence. In Woodcock (1998), gf represents high complexity information processing, whereas gc is a component of declarative and procedural knowledge. Important evidence for gf and gc was presented in Carroll's (1993) monumental review and analysis in the domain of human abilities. The model comprises gf and gc, but the structure presented by Carroll differs from that presented in Cattell (1987, 1998) in that visual and auditory perception occur as second-order factors like gf and gc and not as provincial factors. Apart from the integrative models of intelligence listed above, a great deal of research has related gf and gc to very different theoretical approaches. gf has been related to cognitive correlates, for example, by Kyllonen and Christal (1990), who found a strong relationship between reasoning measures, which they also consider to be measures of gf, and working memory. Correlations between processing speed and gf have been interpreted within the mental speed framework (for example, Rabbitt, 1996).

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