Flavor binding: Its nature and cause

The brain binds inputs from multiple senses to enhance our ability to identify key events in the environment. Understanding this process is based mainly on data from the major senses (vision and audition), yet compelling examples of binding occur in other domains. When we eat, in fact taste, smell, and touch combine to form flavor. This process can be so complete that most people fail to recognize that smell contributes to flavor. The flavor percept has other features: (a) it feels located in the mouth, even though smell is detected in the nose and taste on the tongue, and (b) it feels continuous, yet smell is delivered in pulses to the nose during eating. Furthermore, tastes can modify smell perception and vice versa. Current explanations of these binding-related phenomena are explored. Preattentive processing provides a well-supported account of taste-to-tongue binding. Learning between taste and smell can explain perceptual interactions between these senses and perhaps localization of smell to the mouth. Attentional processes may also be important, especially given their role in binding the major senses. Two are specifically examined. One claims that the failure to recognize smell's role in flavor stems from the role of involuntary attention's "defaulting" to the mouth and taste (i.e., binding by ignoring). Another claims that taste and smell form a common attentional channel in the mouth, in effect becoming one sense. Except for preattentive processing, the mechanisms involved in flavor binding differ markedly from those proposed for the major senses. This distinction may result from functional differences, with flavor supporting future food choice but not current identification.