Limitations on infants' response to rate-based auditory-visual relations.

Investigations of infants ’ response to temporally based auditory-visual unity specified by repetition rate and/or synchrony have yielded inconsistent results, with some studies reporting intersensory matching and others none. The purpose of the current experiments was to determine whether previous failures to obtain rate/synchrony-based intersensory matching could be overcome by providing infants with an initial opportunity to become familiar with the specific types of auditory-visual relations that they would be subsequently tested with. Across several different experiments, 4-, 6-, and 8-month-old infants were first habituated either with (a) a single, temporally concordant auditory-visual compound stimulus, (b) a single, temporally discordant compound stimulus, (c) two different, temporally concordant compounds, or (d) a silently moving visual stimulus. Following habituation, they were given an intersensory paired-preference test where they viewed two side-by-side visual stimuli moving up and down at different rates, and listened to a sound pulsing on and off at the same rate and in synchrony with the direction reversal of one of the visual stimuli. The most consistent and robust finding was a preference for the visual stimulus that moved at a novel velocity, indicating that the temporal attributes of the visual component dominated responsiveness. Only one experiment yielded limited evidence of intersensory matching; infants who were habituated with a silently moving visual stimulus preferred the sound-specified visual stimulus in the presence of the rapid auditory stimulus but did not prefer the sound-specified stimulus in the presence of the slow sound. No effects of prior short-term exposure to the various temporal features of the stimuli subsequently presented during the test phase were obtained. It is