Sensory dominance in infants: I. Six-month-old infants' response to auditory-visual compounds.

Abstract

A series of studies was conducted with 10-month-old infants in which their response to temporally modulated auditory-visual compounds was examined. The general procedure consisted of first habituating the infants to a compound stimulus (consisting of a flashing checkerboard and a pulsing sound) and then testing their response to it by presenting a series of trials where either one or two temporal attributes of the visual, the auditory, or of both components were changed. When the auditory and visual components were temporally identical, during the habituation phase, the infants only encoded the temporal attributes of the auditory component. When the two components were temporally distinct, or when they were identical but when multiple discriminative cues were available, the infants encoded the temporal aspects of both the auditory and the visual components. When the information context was made more complex, the infants' performance deteriorated, but when the salience of the visual component was increased the infants' performance improved. In sum, although the auditory modality can dominate the visual modality at 10 months of age, the visual modality can process temporal information when the temporal relationship of the information in the two modalities is distinct. Most of the research on sensory/perceptual development in human infants has been concerned with the functional characteristics of single sensory modalities. Only quite recently have investigators begun to examine the way that sensory systems interact with one another during early development (Rose & Ruff, 1987). Most of the research on intersensory interaction has, however, been concerned with the detection of intersensory equivalence. The implicit assumption of all this work has been that the sensory systems operate on an equal footing. Given that the structural and functional aspects of the different sensory systems develop asynchronously (Bronson, 1982; Gottlieb, 1971; Kasatkin, 1972; Volokhov, 1968), however, the possibility that sensory dominance hierarchies operate during early development and that their nature may change during this time must be considered seriously. In a companion article, Lewkowicz (1988; see pp. 155-171, this issue) reported on a set of studies that investigated 6-monthold infants' processing of temporally based auditory-visual compounds. The general purpose of those studies was to investigate the relationship of the auditory and visual modalities when information from each of them competed for the infant's attention. Specifically, these studies systematically determined whether responsiveness to information in one sensory modality