Neural Adaptability: A Biological Determinant of Behavioral Intelligence

Abstract

Despite a history of attempts, neuroscience has thus far failed to identify a validated biological determinant of behavioral intelligence. Cognitive variables such as selective attention, expectancy and information processing workload modulate the amplitude of evoked cortical potentials (EPs), thereby demonstrating the operation of cognitive neural adaptability. It seems reasonable to postulate that individual differences in this aspect of neural function could relate to individual differences in behavioral intelligence: the electrophysiologically adaptable brain should be the behaviorally bright brain.

To test this hypothesis I gathered auditory EPs from 109 normal and 52 mentally retarded adults under three stimulation conditions (periodic, self, and random) designed to manipulate temporal expectancy.

The normal adults showed a strong temporal expectancy effect on their EPs, giving smaller than average EPs to expected inputs and larger than average brain responses to unexpected stimuli. In contrast, the retarded adults failed to show a temporal expectancy effect on their EPs, indicating a deficit in neural adaptability. A measure of neural adaptability derived from EP amplitude ratios correlated. 66 with IQ scores obtained on 74 normal adults, indicating a definite association between neural adaptability and behavioral intelligence. People who gave larger than average EPs to unexpected inputs and smaller than average EPs to stimuli whose timing they knew tended to have higher IQs.

Results suggest that the brain which efficiently inhibits its response to insignificant inputs and orients vigorously to unexpected, potentially dangerous stimuli is also the brain which manifests high behavioral intelligence. Neural adaptability as indexed by the temporal expectancy effect on evoked cortical potentials provides a biological determinant of behavioral intelligence.