General intelligence and the definition of phenotypes.
From Spearman's famous 1904 paper to Carroll's recent book on factor analytic results from a multitude of studies, there has been one consistent conclusion: 'g', or general intelligence, is the factor that defines the phenotype for intellectual functioning. It is no overstatement to say that g is undoubtedly the most important psychological construct discovered in this century. It predicts more and is implicated in a wider range of behaviour than any other psychological construct. The empirical support for g is extensive and overwhelming. It would seem that g is the perfect phenotypic definition of intelligence. I argue that it is not the perfect phenotype. If we are to understand intelligence, we need to define a new, more elaborate definition of intelligence taking g as the starting place. It must be remembered that g is a statistical abstraction. Current formulations of g are largely silent about the composition of g. I argue that g is actually made of further separable basic cognitive processes and does not represent a single underlying entity. These basic cognitive processes are integrated into a complex system in the brain that makes them difficult to identify. None the less, until these basic processes are identified and related to brain function there are a number of findings that cannot be explained and this will inhibit scientific progress.
Department of Psychology, Case Western Reserve University, Cleveland, OH 44106, USA.
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Detterman
D001921:Brain / Q000502:physiology; D003071:Cognition; D004522:Educational Status; D005163:Factor Analysis, Statistical; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D007360:Intelligence / Q000235:genetics / Q000502:physiology; D007361:Intelligence Tests; D010641:Phenotype; D011594:Psychometrics; D018709:Statistics, Nonparametric