The idea of the sensorimotor approach is to say that feel is constituted by having cognitive access to the fact that one is currently engaged in exercising a sensorimotor skill. Each of the concepts (cognitive access, engaged, exercising, sensorimotor, skill...) in this rather complicated definition will be defined in detail in later sections. However before, it is worth first considering a simple example which makes clear the advantage of using a skill approach.
Consider a person squeezing a sponge and experiencing the feel of softness. Where does the feel derive from? Clearly the feel of softness resides in the fact that the person is currently attending (more precisely: having "cognitive access" — see later) to the fact that he is in a situation where a certain predictable set of possible sensorimotor interactions exist that are characteristic of softness: interactions like the fact that IF the person presses, the sponge squishes.
This way of thinking about the feel of softness avoids the problem of Question 1: having to find a neural mechanism that generates the softness. This is because under the new view it actually makes no sense to say that the softness feel is generated. Rather, the softness feel consists in the observer having cognitive access to the fact that he is currently engaged in exercising a particular skill, namely the pressing-and-verifying -that-the-sponge-squishes skill. Obviously neural mechanisms are participating in this skill, but they are not in themselves generating the feel of softness.
Taking the skill view now provides a natural way of dealing with the other Important Questions about the softness feel.
Question 2: "Presence" Why does the softness feel feel like something at all? If we took the normal view of feel under which feel is generated by a special neural mechanism, then we could ask what exactly it is about the mechanism that causes it to give rise to a feel rather than no feel at all. After all, most neural mechanisms in the brain or body are not accompanied by any feel.
But under the skill view this question no longer makes very much sense. If what we mean by the quality of a feel resides in the things you do when you engage in a skill, then if you are engaging in a skill, since you are doing something, there must be a quality involved, rather than no quality, and that quality will be different from the quality residing in the other things that you might be doing. Thus by the very definition of feel, if you are having a feel, there must be something it is like for you to have it.
And why does the softness feel have that particular presence that is typical of sensory feels, rather than having no feel at all, as is the case for non-sensory mental states? We suggest that the answer is related to two very important and obvious facts about the particular skills that are involved in sensory feels in general and the feel of softness in particular, and which are generally absent for other types of mental activity: Corporality and Alerting capacity.
Corporality is the fact that movements of the agent's body necessarily provoke systematic changes in the sensory input being monitored in a feel. Alerting capacity is the fact that there are particular (sudden) changes in the sensory input involved in the feel that incontrovertibly attract one's cognitive capacities (e.g. suddenly coming across a sharp needle in the sponge). These important points will be developed later, Suffice it to be said here that Corporality and Alerting capacity are characteristics only of real sensorimotor interactions involving real sensory systems, and not of other brain states. It is this which constitutes the particular "felt" quality of sensory states as compared to other mental states.
Question 3: Sensory quality. Why does the softness feel have the particular quality it has? If we postulated a brain mechanism that generated the feel of softness, this question would be a sensible question, since we could ask, why does the brain mechanism generate precisely the softness feel rather than the hardness or even the redness feel?
But if we take the sensorimotor stance the question becomes superfluous. If currently a person is engaged in noting how the sponge squishes under his or her finger pressure, then by the definition of what we mean by softness, the person is having precisely the softness and not some other feel. To have the hardness feel the person would have to be noting that the sponge resists the pressure. The structure of the perceived similarities and differences between the infinite different possible qualities of softness (very soft, less soft, soft and spongy, resilient, etc.) are exactly the differences and similarities between the different patterns of interaction one can have with corresponding objects.
Question 4: ineffability Why do we have difficulty communicating to others what the feel of softness really feels like to us? The sensorimotor approach has a natural answer to this question which derives from the fact that the quality of the experience of softness is determined by a sensorimotor skill, that is, by a highly complex set of interactions between muscle movements and resulting changes in neural input. Someone perceiving the softness of the sponge knows that he is engaged in exercising the skill of softness, but he does not have cognitive access to the exact muscle movements he is or could be exercising, nor to the exact changes in sensory input that would consequently arise. The ongoing neuromuscular microstructure of the skill is in some sense encapsulated and cognitively inaccessible. On the other hand the perceiver knows which of many possible skills he is engaged in (the softness, rather than the hardness or the smoothness skills for example), and may, with practise and familiarization come to be able to distinguish different modulations of a skill, corresponding, for example, to degrees of softness. An analogy is whistling: you are able to change the notes, but you have little idea exactly what you do to make the notes.
In conclusion, the skill approach seems quite reasonable as far as the softness of the sponge is concerned. But what about seeing red or hearing a bell? If we could apply the skill approach to these more basic cases of "raw feel", we might reap the same benefits we did for softness, that is, we might be better placed to answer The Important Questions as to the origin and nature of feel. In the following we spell out with greater precision the key concepts that are used in the sensorimotor approach, and then in later sections apply the theory to seeing, hearing and touch.
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