Habituation Rate and the Infant's Response to Visual Discrepancies

A simple visual stimulus was repeatedly presented to 120 infants 12 and 18 weeks of age until visual fixation reached a habituation criterion. A discrepant stimulus followed that varied in its magnitude of discrepancy from the familiar standard. In contrast to the age effects observed for the rate of habituation (though they interacted with specific stimuli), there were no age differences in the distribution of fixation times to the several magnitudes of discrepancy. Infants who habituated rapidly displayed an inverted-U curve of fixation as a function of discrepancy in accord with the discrepancy hypothesis, whereas slow habituators gave their maximum response to the largest discrepancy.