The Ability of Four-Month-Olds to Discriminate Changes in Vocal Information in Multimodal Displays

Recent investigations into infants' intersensory perception suggest a specific developmental pattern for infants' attention to visible and auditory attributes of dynamic human faces. This work has proposed that infants' perception seems to progress along a sensory continuum: beginning with multimodal sensory cues (e.g., auditory and visual), then visual-cues alone, and finally auditory-cues alone. Additionally, research has proposed that amodal or invariant sensory information directs infants' attention to specific redundant aspects in the surrounding environment (e.g., temporal synchronicity). The current research attempted to clarify the potential methodological confounds contained in previous investigations into infant intersensory development by contrasting infant behavior within fixed trial and infant-controlled habituation procedures. Moreover, the current research examined infants' attention to auditory manipulations within multimodal displays when redundant sensory information (synchronicity) was or was not available.

In Experiment 1, 4-month-old infants were habituated to complex audiovisual displays of a male or female face within an infant controlled habituation procedure, and then tested for response recovery to a change in voice. For half the infants, the change in voice maintained synchronicity with the face, and for the other half, it did not. The results showed significant response recovery (i.e., dishabituation) to the change in voice regardless of the synchronicity condition. In Experiment 2, 4-month-old infants received the same face+voice test recordings used in Experiment 1, but now within a fixed trial habituation procedure. Again, synchronicity was manipulated across groups of infants. In contrast to Experiment 1, the infants in the fixed-trial experiment failed to show evidence of voice discrimination.

These results suggest that infant controlled procedures may be more sensitive to infant attention, especially in terms of complex social displays. In addition, synchronicity appeared to be unnecessary in terms of infants' ability to detect vocal differences across multimodal displays. In sum, these results highlight the importance of research methodology (e.g., infant control) and overall stimulus complexity (e.g., discrete vs. complex) involving studies of infants' intersensory development.