Organization of abilities and the development of intelligence.

Performances which are accepted as indicators of intelligence are interrelated in ways which indicate 2 broad factors. Each factor represents a kind of intelligence. The 1st, called crystallized intelligence, indicates the extent of acculturation as it determines human abilities. The other, called fluid intelligence, indicates a pattern of neuralphysiological and incidental learning influences. The 2 become independent as development proceeds from infancy to adulthood. Measures of fluid intelligence are the more sensitive indicators of brain malfunction; fluid intelligence declines with brain damage and aging in adulthood. Performances on ability tests involve processes in addition to those of intelligence. These are associated with sensory modality functions (visual, auditory, tactile processes), perhaps indicate endocrine functions (in speediness), represent “strategies or styles of performance (carefulness, speediness), and relate to motivation (need for achievement). Results in support of the theory are presented and evaluated. Some needed research is indicated.