The unity of haptic touch

Haptic touch is an inherently active and exploratory form of perception, involving both coordinated movements and an array of distinct sensory receptors in the skin. For this reason, some have claimed that haptic touch is not a single sense, but rather a multisensory collection of distinct sensory systems. Though this claim is often made, it relies on what I regard as a confused conception of multisensory interaction. In its place, I develop a nuanced hierarchy of multisensory involvement. According to this hierarchy, touch turns out to be a single modality in that its various receptors assign their features to the same tangible objects. When we grasp an object a range of distinct properties-shape, warmth, heft, texture, etc.-are all felt to belong to the object, just as different visual properties are associated with a visual object. Paradigm multisensory experiences, on the other hand, involve associations between distinct perceptual experiences, as when the way something looks affects the way something sounds. Thus despite its functional and physiological diversity, haptic touch can be regarded as a single sense.