External cues in the control of food intake in humans: the sensory-normative distinction.

We review the history of "external cues" as an important factor in the control of human food intake. We begin with Schachter's proposal that obese individuals are especially (and perhaps exclusively) responsive to external food cues and examine subsequent modifications and challenges to that model and the decline and resurgence of research on external cues. We introduce a distinction between normative and sensory external cues. Normative cues (e.g., portion size) refer to indicators of appropriate intake, whereas sensory cues (e.g., palatability) refer to the hedonic appeal of the food. We propose that normative cues affect everyone, whereas sensory cues, while affecting everyone, have a more powerful effect on some types of individuals (e.g., the obese) than on others.