Learning a Novel Coordination - The Dynamic Pattern Hypothesis

Other coordination posts are here.

Recall this image:

The HKB potential function, ~1Hz

This basic layout is supposed to describe an intrinsic state of affairs, namely that only 0°and 180°are stable coordinations (+/- 180° are identical except for which limb is lagging and which is leading). If you look at this function, you will see that potential energy is a maximum at +/90; this suggests that 90°is a maximally unstable coordination (i.e. it takes the most energy to maintain and is susceptible to perturbations which will make behaviour 'run off' towards one or other attractor). This is indeed the case, empirically; people can do it but fail to respond to the inevitable errors that accumulate and they lose the coordination very rapidly.

The question then is: can you learn to move at 90°? Is this dynamic pattern modifiable by experience?

Assume the Cow is a Sphere

One of my favourite jokes goes like this:

A physicist, an engineer, and a psychologist are called in as consultants to a dairy farm whose production has been below par. Each is given time to inspect the details of the operation before making a report.

The first to be called is the engineer, who states: “The size of the stalls for the cattle should be decreased. Efficiency could be improved if the cows were more closely packed, with a net allotment of 275 cubic feet per cow. Also, the diameter of the milking tubes should be increased by 4 percent to allow for a greater average flow rate during the milking periods”.

The next to report is the psychologist, who proposes: “The inside of the barn should be painted green. This is a more mellow colour than brown and should help induce greater milk flow. Also, more trees should be planted in the fields to add diversity to the scenery for the cattle during grazing, to reduce boredom”.

Finally, the physicist is called upon. He asks for a blackboard and then draws a circle. He begins: “Assume the cow is a sphere....”.

A brief rant about waist-to-hip ratio

This is a bit off topic, but it's a good illustration of William James' notion of the psychologist's fallacy and it addresses a pet peeve of mine.

Evolutionary psychology is becoming more and more popular and the media is one of its biggest fans.One thing that annoys me is how quickly and uncritically people latch on to these stories and use them to justify the status quo. One of the most popular stories is that men prefer women with small waists and big hips. This is measured using the Waist to Hip Ratio (WHR). The WHR is the circumference of your waist divided by the circumference of your hips. The links below will tell you that men are irresistibly drawn to women with WHRs of .70. This number is apparently imbued with evolutionary significance because prepubescent girls have WHRs close to 1 (their waists are the same size as their hips), while post-pubescent girls have WHR less than 1 (waists smaller than hips); and also because low WHRs are associated with a good hormonal balance. One thing that makes this idea attractive is that it conforms to our modern, western experience - many women who are considered to be extremely attractive have low WHRs and it's difficult to generate examples of women who are famous for their beauty, but who have high WHRs. This evolutionary angle legitimizes our society's standard of attractiveness. We assume that everyone else basically shares our own preferences (the psychologist's fallacy), so, rather than this result simply telling us something about modern, western mens' judgments of attractiveness, there is the irrisitable pull to generalise this preference to ALL men.

"Moving Through Time" and embodied cognition

In which I am a bit rude about a rubbish paper and worry about how to kill papers like it.

The term 'embodied cognition' has been checked out of the library by a lot of different people, all of whom use it to mean something different. My least favourite definition comes from the cognitive literature, which considers embodiment to be about how internal, abstract cognitive function can be 'revealed' motorically (the Barselou (2008) version of embodiment). This definition is rooted firmly in the assumption of mental representation. For me, embodiment is only interesting if it contributes in a meaningful way to what cognition is, and thus I define embodied cognition in the other direction - embodied cognition is about how cognition is shaped by the kind of perceiving-acting organism we are.

Coordination and the Haken-Kelso-Bunz Model

Other coordination posts are here.

Now we have the basics out of the way, we can explore some of the key characteristics of coordinated rhythmic movements.

Kelso's early experiments established a set of basic phenomena. Recall that, at the moment, the task is to wiggle your fingers in and out (towards the midline) at some mean relative phase and at some frequency. Moving your fingers in-phase (0° mean relative phase) has the fingers moving in the same direction at the same time, and entails the co-activation of homologous muscle groups in each hand.

Coordinated rhythmic movement. - an introduction to an experimental paradigm

I have some papers I wanted to talk about, but it occurred to me that they only make sense in a context. So I'm going to spend some time talking about the experimental task I use a lot, why it's interesting and what we can learn from it about perception and action.

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To a man with a hammer, everything looks like a nail. My hammer is coordinated rhythmic movement, and I use it to study everything I'm interested in - perception-action, learning, ageing, you name it. This task is a workhorse of the perception-action literature and has been since Kelso described it in 1981 (after the task was, as far as I can find, first described by Cohen, 1971).

Rebooting the blog

The curse of only occasionally writing a blog is that when other things intrude (like real work) the blog tends to suffer. A bunch of work plus finishing reading Heft lead to this hiatus (once Heft's covered Gibson, he moves onto Roger Barker and while Barker seems like an interesting (and very ecological) researcher his interests fall quite convincingly outwith mine. So blogging about it seemed a little pointless.).

The question is, where next? I plan to re-read Radical Embodied Cognitive Science and blog that, now that I've had time to digest it, think about it, and get more into the 'affordances-are-dispositions' vs '-are relations' argument. We may yet also write a couple of papers on that, so stay tuned.

In the meantime, I'm keen to get back into the discipline of writing a couple of times a week. I may devote one post to reviewing specific papers; I'm developing two grants using coordinated rhythmic movement and I've been reading and developing the arguments for a while now. There's an interesting tension in the literature on this, and I've finally gotten two key papers on this topic in press so I can finally begin to really get moving on this topic. I think one post a week will be on a paper by myself or someone else which I can use to highlight the various theoretical conflicts.

It's not like anyone's reading :v