753 Perceptual Development: Intermodal Perception Trehub, S. E. (2003). The developmental origins of musicality. Nature Neuroscience, 6, 669–673. PERCEPTUAL DEVELOPMENT: INTERMODAL PERCEPTION Speaking faces, baking bread, speeding cars—the world provides a richly structured, continuously changing stream of stimulation to all of our senses. Intermodal perception (also called intersen- sory or multimodal perception) refers to percep- tion of information from objects or events available to multiple senses simultaneously. Because most objects and events can be seen, heard, and touched, everyday perception is primarily intermodal. Despite the fact that information about the world is carried through different sensory channels that each provide distinct forms of stimulation, we are able to perceive a stable world of unitary objects and events (people speaking, cars honking), rather than separate sights, sounds, and tactile impres- sions. The senses work together as a coordinated perceptual system, even in newborns, and inter- modal perception develops rapidly and with increasing specificity across infancy. How we accomplish this “integration” is a puzzle that has fascinated philosophers and scientists for centu- ries. This entry covers the history and theory of intermodal perception, as well as aspects of the development of the senses as they relate to inter- modal perception. History and Theory Over 2,000 years ago, Aristotle proposed a sensus communis, or common sense, to explain how we perceive qualities common to different senses, such as number, form, and unity. Centuries later, phi- losophers such as John Locke and George Berkeley proposed that we needed to integrate information across separate sensory channels before perceiving a unified object or event, such as a bell ringing, rather than perceiving separate streams of light and sound. This posed a “binding” problem for perception, in that the brain would need to some- how unify separate channels of sensory informa- tion to “construct” a coherent world. This constructivist view dominated thinking throughout most of the 20th century, including Jean Piaget’s well-known theory of cognitive development. Piaget proposed that integration took place gradu- ally over the first year of life through interacting with objects and coordinating information across the senses. Prior to integration, infants were thought to perceive a world of unrelated sights, sounds, smells, and tactile impressions, much like the “blooming, buzzing confusion” described by William James in 1890. Not until the psychologist James J. Gibson pub- lished his work on ecological perception in 1966, The Senses Considered as Perceptual Systems, was this constructivist view seriously questioned. Gibson argued that our senses work together as a unified perceptual system, and that the existence of different forms of sensory stimulation was an advantage rather than a disadvantage for percep- tion of unified objects and events. This is because we perceive amodal (not tied to a particular sense modality) information that is redundant or identi- cal across the senses. This includes temporal syn- chrony, rhythm, duration, tempo, changes in intensity, and spatial location common to audiovi- sual events, and shape, substance, size, and texture common to visual–tactile events. Because all events occur over time and space, all events provide amodal information. Gibson’s theory is considered a differentiation view of development. In contrast to the integration view, which holds that the senses are separate at birth, the differentiation view, articulated by Eleanor J. Gibson, proposes that the senses are unified at birth and that perceptual development is characterized as a gradual process of differentiat- ing increasingly finer levels of sensory stimulation. From this view, now widely accepted among devel- opmental psychologists, there is no “blooming, buzzing confusion” in early development. Rather, infants detect many general features of unified multimodal events from birth and learn to perceive increasingly more subtle differences and more complex objects and events through looking, lis- tening, and interacting with their environment. Importance of Amodal Information and Intersensory Redundancy for Development How do infants learn to detect unified multimodal events such as a person speaking? Evidence indicates