Intersensory redundancy guides attentional selectivity and perceptual learning in infancy

Abstract

This study assessed an intersensory redundancy hypothesis, which holds that in early infancy information presented redundantly and in temporal synchrony across two sense modalities selectively recruits attention and facilitates perceptual differentiation more effectively than does the same information presented unimodally.Five-month-old infants' sensitivity to the amodal property of rhythm was examined in 3 experiments.Results revealed that habituation to a bimodal (auditory and visual) rhythm resulted in discrimination of a novel rhythm, whereas habituation to the same rhythm presented unimodally (auditory or visual) resulted in no evidence of discrimination.Also, temporal synchrony between the bimodal auditory and visual information was necessary for rhythm discrimination.These findings support an intersensory redundancy hypothesis and provide further evidence for the importance of redundancy for guiding and constraining early perceptual learning.The newborn infant encounters a world of objects and events that present a richly structured array of stimulation to all the senses.Recent research demonstrates that young infants are adept perceivers of this multimodal stimulation (see Lewkowicz & Lickliter, 1994;Rose & Ruff, 1987).Infants do not perceive disparate sensations through the various sense modalities; rather, they are able to select information that is meaningful and relevant to their actions and to perceive coherent, unitary multimodal events even in the first months of life.For example, 2to 5-month-old infants are able to perceive a relationship between a face and a voice on the basis of temporal synchrony, shared rhythm, and spectral information between the movements of the mouth and the timing and nature of the speech sounds (Dodd, 1979;Kuhl & Meltzoff, 1984;Mendelson & Ferland, 1982).By 5-7 months, infants can also match faces and voices on the basis of the age and gender of the speaker as well as the speaker's affective expression (Bahrick, Netto, & Hernandez-Reif, 1998;Walker-Andrews, 1982;Walker-Andrews, Bahrick, Raglioni, & Diaz, 1991).Infants of 3-6 months are also able to match a soundtrack to the appropriate one of two objects hitting a surface on the basis of the object's substance and composition (Bahrick, 1983(Bahrick, , 1987(Bahrick, , 1988(Bahrick, , 1992)).Although there is now a solid base of data demonstrating that infants are adept perceivers of multimodal stimulation across a variety of natural events, as yet little is currently known about how infants accomplish this.How and on what basis do infants begin to parse, perceive, and derive meaning from the flux of multimodal stimulation in a manner that lays a foundation for the perceptual world of the adult?Consistent with Gibson's (1969) invariant detection view, Bahrick (1992, 1994;Bahrick & Pickens, 1994) has proposed that amodal information initially guides this developmental process.Amodal information is information that is not specific to a particular sense modality