The essay integrates the psychometric intelligence approach with the cognitive-developmental approach or the stage theory erected by Piaget and his disciples. The latter led to Piagetian Cross-Cultural Psychology and the accumulation of an immense body of data. It shows that different IQ levels are indicative of the peculiar stages of cognitive…

Reviews the current theories concerning individual differences in cognitive functioning. While some argue that heredity places a genetic cap on intellectual development, others emphasize the dynamic interrelationship between cultural and environmental factors. Concludes that intelligence is more complex than the heredity advocates allow. (MJP)