Cross-modal equivalence in early infancy: Auditory–visual intensity matching.

It has been proposed that young infants are attentive to quantitative variations in stimulation to the exclusion of qualitative ones. To the extent that this is so, young infants should ignore differences between lights and sounds and should instead respond to auditory and visual stimuli as more or less similar depending on their intensity. To examine this hypothesis, a cardiac habituation/dishabitua-tion method with a test for stimulus generalization was employed. Three-week-old infants were repeatedly presented with white-light followed by white-noise stimuli of different intensities. A U-shaped relationship between magnitude of cardiac response and loudness was found. In view of previous findings that without prior visual stimulation a monotonic increase in cardiac response to the same range of auditory stimuli results, this finding of a significant quadratic relationship with loudness suggests that the infants were responding to the auditory stimuli in terms of their similarity to the previously presented visual stimulus. A separate group of infants presented with a more intense visual stimulus exhibited a shift in the intensity at which a minimal cardiac response occurred. Results of a study with adults did not show any systematic relation-ship between cardiac response and loudness, indicating that unlike infants, adults do not spontaneously make cross-modal matches of intensity. Our perception of the world is based to a large extent on experiences that are multi-sensory in nature. There are a number of different ways in which such multisensory inputs may interact (Turkewitz McGuire, 1978). The present article is concerned with intersensory interaction in which inputs from different modalities are responded to as equivalent. Such interaction may be based on responses to a variety of features arising from the stimulus situation. Broadly