The Salience of Multimodal Sensory Stimulation in Early Development: Implications for the Issue of Ecological Validity.

Studies of infant development concerned with the emergence of specific perceptual or cognitive abilities have typically focused on responsiveness in only one sensory modality. Research on infant perception, learning, and memory often attempts to reduce multimodal stimulation to "noise" and to control or omit stimulation from other sensory modalities in experimental designs. This type of unimodal research, although important, may not generalize well to the behavior of infants in the multimodal context of the everyday world. Research from animal and human development is reviewed that documents that significant differences in infants' perceptual skills and abilities can be observed under conditions of unimodal versus multimodal stimulation. These studies provide converging evidence for a functional distinction between unimodal and multimodal stimulation during early development and suggest that ecological validity can be enhanced when research findings are generalized appropriately to the natural environment and are not overgeneralized across stimulus properties, tasks, or contexts.