What Does The Brain Do, Pt 2: The Fast Response System

I want to continue thinking about the implications of the claim that the brain does not trade in representations. I'm not looking to defend this view here; we got into it a bit last time, I've talked about it here, and if you can't imagine what cognition without representation might look like, then you should read this post by Sabrina and then Radical Embodied Cognitive Science before worrying me with your lack of imagination. If you then feel like getting into it, Sabrina is tackling this topic in detail, beginning here.

If the brain isn't mentally representing, what is it doing? Last time, I got into the idea that the brain is part of a embodied cognitive system. It's in the middle of a rich information flow, with access to perceptual information about the world and ourselves, and it's a critical part of the action system, involved in our responses to that information. I talked about it as the fast response system in the set of inherent dynamical resources available for us to use to form task specific devices; I want to expand on that a little.

Fast Response System

The task specific device approach is primarily a methodology; instead of trying to study the perception-action system in general, you acknowledge that this system is too high dimensional, flexible and non-linear and instead focus on studying performance in well defined task spaces to identify how the system solves specific problems. It is also, however, how I think the system itself solves the problem. Right now, as I sit typing this, my perception-action systems are not trying to effect any of the other things I can, in principle, do. I am not, at this moment, actually capable of running. I have the ability to form a running device; but that, I think, is not the same thing. So the perception-action system resolves the 'degrees of freedom' problem by only trying to solve the problems at hand, using the resources available.

Such a system requires a) rich perceptual contact with the environment, and b) the ability to transition from one device to another, in response to changes in the environment. (This 'environment' can include internal states, such as goals and intentions - but I don't really know how to talk about these rigorously yet so I want to leave that for now.) The ability to switch the entire device between states takes time (inherent dynamical resources such as muscles and cardiovascular system all have inertia and particular response characteristics; change takes time, in other words). The nervous system doesn't have much in the way of inertia to overcome; it can, roughly, turn on a dime, and respond on a time-scale that will match the changing flow of information. It can therefore lead the formation of the next device.

One of the critical features of task specific devices is that they are, to a certain extent, functionally encapsulated. What I mean by this is that devices literally use some resources and not others; those being used are temporarily 'walled off' from those not being used, so that changes to irrelevant resources don't unnecessarily affect behaviour. This fact underpins the perturbation experimental method (which I've described here for action components, and here for perceptual components).

Which parts are 'walled off' into coherent systems changes over time as you go from being one device to another. You therefore need to be able to temporarily couple these components into systems with specific composition and organisation, and then dis- and re-assemble them into the next system. As I discussed last time, most of our inherent dynamical resources are quite stable over time (e.g. the link-tendon system; muscle composition), and the coupling between these systems is often physical and not malleable. Our entire body is innervated by the nervous system, however, and it's speed and flexibility is the mechanism that allows for the temporary coupling of disparate resources into stable devices.

Which device gets made?
There is, of course, the question of which device to make. Traditional motor programming type theories (such as Schmidt's 'generalised motor programme' approach) hold that you call up a set of commands for producing a class of movements, and, in response to cues from the environment, you set the parameters of that schema (how fast, how far, etc) to produce a specific movement. In essence, you must retrieve from memory a schema that contains what you've learned about that kind of movement, and only then adjust it. Sabrina discussed this topic in great detail here - this structuralist approach assumes that we must have stored a discrete object of some kind, which we can then tailor to suit the local demands. This approach is fraught with problems: how many of these can we store? How long does it take to find and retrieve the right one? How do we pick the right one? What sort of commands are stored in the programme, given how context sensitive movement is (moving to the same location in space can be achieved by a large number of different movements - the mapping is therefore many-to-one)? Given the more functionalist approach I am advocating, this is clearly not what I think is going on. So what do I think is happening?

I always think about batting in softball as an example of this. When you're going out to bat, you pick up the bat, and stand 'on deck' waiting your turn. In between pitches, we all swung our bats, warming up. When it was my turn, I'd get my feet planted and stand by the plate; I'd touch the far corner of the plate with the bat to get a sense of where the strike zone was and swing the bat a few more times from that stance. I'd also often let the first pitch go by, just to watch it. All of this was on the advice of the better players in our team.

What I was doing was generating information that was guiding the formation of a softball-hitting device. Swinging the bat generates information about it's inertial characteristics, which is the basis of dynamic touch (discussed at the end of this post on Chemero's book). I now have information about how the bat is changing my upper limb functionality, as well as information about what's required to move the bat (how long it takes, etc). Repeating this at the plate continues this flow of information in a more specific setting, driving the continued formation of the right kind of device. Watching the first pitch go by was also a way of sampling some task relevant information without yet trying to interact with it. My claim is that this is all happening in the moment; until I pick up a bat, I am not currently capable of swinging a bat. The job of the nervous system is to enable the formation of that device once I begin the process, and the specific device I form is the result of the structure of the flow of information and the kind of nervous system and body it's flowing into.

Conclusion
The job of the nervous system is not to store discrete representations with motor commands that produce a given response. Our skilled actions are exquisitely responsive to environmental demands and it's not clear that tweaking a discrete set of categorical movement types could possibly account for this. Instead, the nervous system is reshaping itself in response to the changing flow of information, and that new shape couples inherent and incidental dynamical resources into the task specific device you are capable of making that is related to the task at hand. The current form of the nervous system, like the current form of all our inherent dynamical resources, reflects how it is currently being used, and while there are, of course, identifiable changes you can relate to that use, those are not representations, and the only reason they are described as such is because representations are assumed; this kind of imaging result is not independent evidence for representation.

How good your device is, of course, depends on practice and learning, and what I haven't yet touched on is the other putative role for the brain - memory. Why was it that when I picked up a bat I began forming that device? Because that's what I had practiced. What was the consequence of that practice that remained so that I could use it again later? If I was a structuralist I would say 'procedural memory'; a thing, an object, that contained the results of that practice in some format. As a functionalist, I want to say 'perceptual learning'; through use, I have come to learn what that information means, and what it means has to do with swinging a bat to hit a softball. This is clearly not good enough, but it's next on my list to tackle, so hang tight :)

A Final Note: Part of the problem with which I'm struggling is finding ways of describing what the brain is up to in my terminology, without sounding like I'm merely redescribing what we already know. I think the brain is up to radically different things that representationalists, but often I'm talking about the same overall behavioural effect (like the softball bat) with no clear evidence that my different mechanism is actually the right one. Modern neuroscience has 'explained' many if not all of the kinds of phenomena I need to explain too, so I will eventually need to be able to distinguish these accounts empirically. But a) I can't rely much on the existing literature because it's framed incorrectly for me to use, b) I'm not a neuroscientist and won't be running more useful studies any time soon, and c) right now my goal is to start from the ground and work my way back up, exploring the consequences of my differing starting point (inspired by what I like most about Gibson, 1979). I'm not even close to completing this; these posts are just my thinking out loud, and so yes, I know I have no slam dunk. What I do need, though, is continuing feedback about the logic of my approach, and awkward questions about things you see as weaknesses continue to be very welcome!

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