1 Development Across the Life-Span: The Case of Intersensory Perception Robert Lickliter Department of Psychology Florida International University As we all know, adults are exquisitely skilled at selectively attending to specific features or aspects of objects and events, picking out information that is relevant to their needs, goals, and interests, and ignoring irrelevant stimulation. For example, we easily pick out a friend in a crowd, follow the flow of action in a ball game, and attend to the voice of the speaker at a cocktail party in the context of competing conversations. We long ago learned to pick out human speech from non-speech sounds and parse continuous speech into meaningful words by ignoring variations across speakers, accents, and intonation. Similarly, we have learned to parse the visual array into coherent objects and surfaces despite variation due to lighting and shadow and interruption of surfaces due to occlusion. The foundations of these remarkable skills, easily taken for granted by experienced perceivers, develop across infancy as a result of ongoing experience with objects and events. This rapid perceptual development depends on improving attentional allocation and economy of information pick up for relevant aspects of the environment. In this light, the newborn infant faces a significant developmental challenge following birth - how to become increasingly economical and efficient at attending to multimodal stimulation that is unitary (coherent across the senses and originating from a single event) and relevant to their needs and actions, while ignoring stimulation that is less relevant. This is a challenging task, as the environment provides far more stimulation from multiple objects and events than can be attended at any given time. The infant must learn to attend to variations in incoming stimulation that are meaningful, relevant, and coherent (e.g., coordinated changes in the face and voice of a single speaker amidst unrelated changes in other objects and people) and ignore other variations that are relatively meaningless (differences in lighting and shadow across cohesive objects, variations in speaker voice or intonation across the same phoneme). What factors determine which information is selected and attended to by infants and which information is typically ignored during early development?