Matthew Fulkerson

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.

Rethinking the senses and their interactions: the case for sensory pluralism

I argue for sensory pluralism. This is the view that there are many forms of sensory interaction and unity, and no single category that classifies them all. In other words, sensory interactions do not form a single natural kind. This view suggests that how we classify sensory systems (and the experiences they generate) partly depends on our explanatory purposes. I begin with a detailed discussion of the issue as it arises for our understanding of thermal perception, followed by a general account and defense of sensory pluralism.

Explaining Multisensory Experience

Our experience of the world involves a number of senses, including (but perhaps not limited to) sight, hearing, touch, taste, and smell. These senses are not isolated from one another. They work together, providing a robust and coherent awareness of our environment. Consider entering a good restaurant: one sees the decor and the other patrons, smells the pleasing odors wafting from the kitchen, hears the pleasant music and sound of conversation, feels the comfort of the seating, and, finally, savors the taste of the food. It seems obvious that, in some sense at least, our perceptual awareness of the restaurant is multisensory. Saying exactly what it is for perceptual awareness to be multisensory is more challenging than it appears, however.

Response to Batty's review

Clare Batty has written a careful and insightful review of The First Sense. The critical points she raises are constructive and important, and certainly worthy of extended discussion. Here I offer a short reply to two issues that she discusses. Batty raises a worry about the scope and strength of the unity constraint used to connect the various subsystems involved in haptic touch into a single modality. There are two things to say here. First, on my view the possibilities of bound interaction define the tactual features even in the simpler cases (see p. 50; all references are to Fulkerson, 2013). The various systems involved in visual feature binding are (relatively) well-ordered and clear. We get the right systems not by fiat, but by working backward from the features actually bound together. We use feature binding as a foundation to pick out and define the set of constitutive features for that modality. Then we can say, with some confidence, that experiences with a subset of those features are in the same modality. This explains why seeing a ganzfeld counts as vision: colors are among the features bound by visual subsystems. Feeling warmth or pressure counts as touch because those features are bound by the collection of haptic subsystems. This also explains why tingles, tinges, and pains, even when cutaneous and bodily, should not be classified as part of touch. Second, and more generally, I’m skeptical of attempts to provide necessary and sufficient conditions for the purposes of sensory individuation and for classifying multisensory interactions. This “sensory pluralism” maintains that there is no one way for an experience to be multisensory or unisensory (pp. 18–19). As I wrote, “my claim is that, among the variety of ways in which we can carve up sensory experiences . . . one of them—feature binding—provides an interesting and meaningful sense of unity that applies equally to touch and the other major senses” (p. 19). Like touch, our visual system is complex and coordinated and involves multiple points of convergence and coordination. If we’re worried about the unity of touch, we should worry about the unity of vision too. My claim is that, when comparing apples to apples, touch and the other senses share at least one form of interesting unity.

Affective Touch from a Philosophical Standpoint

This chapter offers a critical philosophical examination of recent work on pleasant (or affective) touch. After developing a distinction between two notions of perceptual affect, I argue that “emotional” and “affiliative” touch are best understood as causing affective reactions, and that affective touch is best understood as perceptually presenting us with affective qualities. In other words, affective touch, unlike other forms of hedonic touch, has a presentational character. On neither model does touch involve anything like a pleasantness detector, nor does it involve a direct relation to or representation of affective qualities understood as objective sensible features of external objects. I suggest an alternative, largely dispositional account of affective touch experiences. Taken together, these reflections aim to provide a detailed framework for better understanding the richness and diversity of affective touch experience.