DEVELOPMENT OF AUDITORY-VISUAL LOCALIZATION

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DESCRIPTION: Most perceptual, cognitive, affective, and linguistic events are specified concurrently in different sensory modalities and are distributed across space and time. Spatial and temporal stimulus features can be represented equally well across modalities and thus provide a major basis for the integration of the heteromodal attributes of multimodally represented events and objects. Empirical evidence indicates that human infants can perceive some of these intermodal attributes and can use them to integrate heteromodal inputs. Most of this evidence concerns infants' perception and usage of temporal aspects of multimodal stimuli, such as synchrony, duration, rate, or rhythm. There has been relatively little research on the role of spatial factors in crossmodal integration, and the results remain equivocal in many cases. Given that spatially integrated multimodal events are a fundamental part of the infant's everyday experience, understanding the processes underlying the development of such abilities is critical. The purpose of the current project is to carry out a systematic investigation of the development of infants' responsiveness to intermodal spatial relations by studying responsiveness to intermodal targets with varying degrees of spatial separation in infants between 2 and 10 months of age. Head- and eye movements will be measured and will be used to investigate developmental differences in infants' responsiveness. A series of seven experiments is proposed to test various aspects of auditory-visual localization. The experimental apparatus has been designed in accordance with previous research of A-V localization in human adults and animals. The latter research will thus provide important baseline data and constraints of for interpreting the results obtained in this project. Standard psychophysical methods (race model analysis) will be employed to establish the mechanisms underlying the multimodal spatial integration process and its development. The empirical work will be complemented by modeling work. The model will incorporate the empirical results, and will provide a framework for the empirical research. The results will: (a) explicate mechanisms underlying the developmental changes in responsiveness to intermodal spatial relations, (b) add to our understanding of the development of a process that enables infants to learn about the psychological unity of their experience, and (c) help further develop and refine measures of perceptual functioning that already have proved to have diagnostic utility in detecting aberrant developmental outcomes.