Search

Two experiments tested 7-month-old infants' ability to categorize events on the basis of invariant rhythm or tempo. Videotaped auditory-visual events (a hammer striking a surface to create characteristic rhythms and tempos) were presented to infants using an habituation procedure. In Experiment 1, following habituation to events depicting one tempo amid three rhythms, infants showed a significant recovery of visual attention to a change in tempo and rhythm, but not to a change in rhythm alone. In Experiment 2, following habituation to events displaying one rhythm amid three tempos, infants did not show a recovery of visual attention to a change in rhythm and tempo, nor to a change in tempo alone. The pattern of results suggested that 7-month-old infants categorized events on the basis of invariant tempo amid changing rhythms, but did not appear to do so for an invariant rhythm in the context of changing tempos.

The ability of 4-month-old infants to learn the arbitrary relationship between an object and a distinctive odor was assessed. Infants were familiarized with two objects while one of them was paired with a cherry odor. Results indicated that only female subjects showed evidence of matching. They increased their looking to the target object in the presence of the odor but not in the absence of the odor, relative to baseline levels.

Infants' intermodal perception of two levels of temporal structure uniting the visual and acoustic stimulation from natural, complex events was investigated in four experiments. Films depicting a single object (single, large marble) and a compound object (group of smaller marbles) colliding against a surface in an erratic pattern were presented to infants between 3 and 712 months of age using an intermodal preference and search method. These stimulus events portrayed two levels of invariant temporal structure: (a) temporal synchrony united the sights and sounds of object impact, and (b) temporal microstructure, the internal temporal structure of each impact sound and motion, specified the composition of the object (single vs. compound). Experiment 1 demonstrated that by 6 months infants detected a relation between the audible and visible stimulation from these events when both levels of invariant temporal structure guided their intermodal exploration. Experiment 2 revealed that by 6 months infants detected the bimodal temporal microstructure specifying object composition. They looked predominantly to the film whose natural soundtrack was played even though the motions of objects in both films were synchronized with the soundtrack. Experiment 3 assessed infants' sensitivity to temporal synchrony relations. Two films depicting objects of the same composition were presented while the motions of only one of them was synchronized with the appropriate soundtrack. Both 412-and 6-month-olds showed evidence of detecting temporal synchrony relations under some conditions. Experiment 4 examined how temporal synchrony and temporal microstructure interact in directing intermodal exploration. The natural soundtrack to one of the objects was played out-of-synchrony with the motions of both. In contrast with the results of Experiment 2, infants at 6 months showed no evidence of detecting a relationship between the film and its appropriate soundtrack. This suggests that the temporal asynchrony disrupted their detection of the temporal microstructure specifying object composition. Results of these studies support on invariant-detection view of the development of intermodal perception.

Four-month-old infants can detect a relationship between the soundtracks and films of rigid and elastic objects in motion. When movies of these two kinds of objects were shown side by side along with the soundtrack to one of them, infants predominately watched the sound films. Three subsequent studies explored the basis of this intermodal perception. It was found that infants detected bimodal temporal structure specifying object rigidity and elasticity, and temporal synchrony between the sights and sounds of object impact. These results support the view that the development of intermodal perception is based on the detection of invariant relations in visual and acoustic stimulation.

This research was undertaken to assess whether 5-month-old infants could discriminate and classify audible and visible, English and Spanish speech passages on the basis of language membership. Forty-eight infants were tested in an infant-control visual habituation procedure. They were habituated to a video display of a woman reciting one of two passages in either English or Spanish. Variables such as speaker identity, meter, number of syllables, affect, facial motion, and speed and intensity of speech were controlled across the English and Spanish versions of each passage. Subjects were randomly assigned to one of three discrimination test conditions: (a) a no-change control, (b) a new passage presented in the old language, or (c) a new passage presented in the new language. It was expected that if infants were capable of classifying passages on the basis of language membership, they would show significant recovery to the new passage when it was presented in the new language, relative to the performance of control subjects, but would generalize habituation across passages of the old language. Results confirmed these expectations. A second experiment identical to the first except for the presentation of silent visual displays demonstrated that classification of languages was not based on visual information for speech. Rather, the auditory information was necessary for classification. These findings are discussed in the context of an invariant-detection view of perceptual development.