Embodied cognition is not what you think it is

The most exciting thing in cognitive science right now is the theory that cognition is embodied. It is, in fact one of the things interested lay people know about cognitive science, thanks in part to a lot of high profile experiments that claim to show how cognition can be influenced and biased by states of the body, or that cognitive states can affect states of the body in ways that suggest abstract metaphors and concepts are grounded in the behaviour of the body. A recent blog post at Scientific American covers this ground quite nicely (although the large picture of Noam "not an embodied cognitive scientist" Chomsky hints that someone didn't actually read the piece).

The problem, however, is that this is not really what embodied cognition is about. Embodiment is not the weak claim that you can see small effects of the behaviour of the body in our mental representations of the world. Embodiment is the radical hypothesis that the brain is not the sole resource we have available to us to solve problems. Our bodies, and the meaning-filled perception of the world they allow, do much of the work required to achieve our goals, and this simple fact changes utterly what our theories of 'cognition' will look like.

Disembodied cognition
The original computational depiction of cognition in the 1960s treats us as general problem solving devices. Similar tasks (e.g. reaching with your left vs. your right hand) are achieved by applying the same underlying general motor programme to the different effector. The body was simply the output system attached to the cognitive processing system; it was cognition that was responsible for all the characteristics of what the body gets up to. More recently, people have begun to realise that the types of bodies contribute non-trivially to the form of our various behaviours, and the idea of 'embodied cognition' began to emerge.

Then, like everything else in psychology, it immediately fractured into approximately 5 different versions. Most of these are wrong, or, at the very least, nowhere near as new as they like to pretend.

What embodied cognition isn't
The most commonly discussed embodied cognition hypothesis that the contents of our mental representations can be affected by states of the body (this is what that Scientific American article considers embodied cognition). For example, the way we mentally represent abstract concepts seem to be influenced by physical metaphors - we might conceive of importance as weight, and thus the weight of things might affect how important we think they are (Jostmann et al, 2009). Another way to demonstrate this is to find changes in states of the body as a function of changes in our mental states; the suggestion is that if the mental state is grounded in a sensorimotor experience, activating the former might also prime or activate the latter. An example of this is the 'moving through time' paper (Miles et al, 2010), in which people thinking about the future tended to sway forwards (on average) and those thinking about the past tended to sway (on average) backwards. (I've critiqued this paper fairly comprehensively here; funny how these tend to show up in Psychological Science!).

Besides the tendency to over interpret tiny effects and generally ignore what the perception-action system might actually be up to, the core problem with these versions of embodied cognition is this - there's nothing new or interesting here. All these papers assume that the contents of cognition are, roughly, what we've thought it was since the 60s - mental representations containing abstract, generalised and computational programmes that enable us to process impoverished sensory data into a perception of the world good enough to support skilled action. The only difference is that these researchers suggest these programmes can be influenced by some of the things we get up to. The strongest claim you will ever hear is that these programmes can finally be grounded, i.e. there is a reason (embodiment) that they have the contents they have.

Why is this such a problem? The hypotheses about these mental states, and what kind of content they have, came from the specific work they have to do in order to enable behaviour. For example, a representation may contain a prior probability distribution that suggests a given pattern of sensory information is probably caused by a particular state of affairs in the world, or it may contain a mapping between an event in the world and the motor system's reponse. This flavour of embodied cognition simply claims that representations still have to do the same kind of work, but that now some of their content might reflect something about the state of the body. This misses the fact that embodiment is actually a much more radical hypothesis, and that it's first implication is that cognition now has a very different job description.

The radical implications of taking embodiment even a little bit seriously
What I think the real hypothesis of embodied cognition is that the type of perception and action systems we have radically alters what 'cognition' needs to look like. My favourite current example is the outfielder problem (how a baseball outfielder is able to catch a fly ball; McBeath et al, 1995), and the contrast between the straight-forward cognitive, predictive strategy versus the perception-based prospective control solutions. The contents of cognition for the predictive strategy includes a) an estimate of the initial conditions of the ball's flight, derived from perception, b) an internal model of projectile motion which can take those initial conditions as input and c) a mapping from that model to the motor control system to allow you to move in the right direction.

The embodied solutions, for which there is clear evidence, utterly change this content. You no longer require an internal model of projectile motion; you simply need the ability to visually perceive the motion of the ball and the experience to move so as to produce a particular pattern to the optical motion of the ball. So it would make no sense to go looking for effects of the body on your internal model of projectile motion, because, when you take embodiment seriously, you cease to think there will be one.

Other examples abound in the literature; some highlights

• rat pup huddling critically depends on the shape of rat pups 
• Barrett (2011) describes the implausible nature of the Portia spider, who accomplishes great feats of complex navigation that emerge from the spatial arrangement of their eyes and the scanning behaviour afforded by that arrangement.
• the size-weight illusion doesn't come from people mentally accounting for object size when perceiving weight, it's the result of people correctly perceiving the throwability of objects
• keas and crows are excellent problem solvers, but do so in different ways that critically depend on the affordances of their bodies
• embodied robots require little in the way of computational power, but are capable of all kinds of flexible behaviour. This behaviour often changes with simple changes to their body structure; Pfeifer & Scheier (1999; see also Pfeifer & Bongard, 2007) described their 'Swiss robots' who clean up their environment because of the relationship between the angle between their light sensors and the simple rule governing their behaviour; change the angle and not the rule, and their behaviour is qualitatively different.

Any good book on embodied cognition will include a review of empirical results like this, and many of the more recent ones (e.g. Barrett, 2011; Chemero, 2009) also tackle examples of embodied solutions to more traditional cognitive tasks involving memory, or abstract problem solving, rather than just the perception-action ones I typically talk about. My bias here is partly because it's the literature I know, but also because my discipline is where a lot of this work has been done. There are, however, an increasing number of researcher in other fields beginning to take this approach seriously.

Pick a side, people
But surely there can be more than one approach to embodied cognition, and my version is no more or less right, just different. Right? Wrong. First of all, this (very typical) argument is one of the main weaknesses of modern psychology - it's time to pick a theoretical side, already, because these things aren't just different, they are often directly contradictory. I'll go into that in my next post.

I don't claim I'm right and they're wrong because I think the specific implementations of embodied cognition I talk about are 'true'. I do so because the underlying theory that produced these implementations is more true to the implications of embodiment. All embodied cognitive scientists claim that the type of bodies we have affect what the final form of cognition will be, but only the second group is taking the implications seriously. The first group have simply taken disembodied cognition and allowed the body to quantitatively affect those states (by a main effect, or, if you're feeling snazzy, an interaction!). The second group have noticed that embodiment actually qualitatively changes what cognition will be; the difference is one of kind. And this is why I say the first group are wrong: they claim to take embodiment seriously, but their research remains business as usual, with a couple of embodied bells and whistles.

A note on representations
The hypothesis of embodied cognition is not necessarily anti-representational; much of it, even the good stuff, is not committed to losing representations. Andy Clark famously reserves some room in his theorising for 'representationally hungry' problems, even though he's happy for embodied solutions to show up a long way into cognitive territory. Barrett's book also doesn't deny representations, although she is quite close to realising she doesn't need them and notes she read Chemero's book too late to work it in detail into hers. But I actually agree with Chemero, that trying to do representational embodied cognitive science is a bit of a category error. You simply end up with an utterly different job description for cognition, and also, I think, for the brain.

One reason psychologists persist with representations is that they simply can't see what else cognition could possibly be, if not representational and computational. There's simply no excuse for this any more, though: Chemero's book is an excellent and clear exposition of a viable alternative framework, one which was first crystallised by van Gelder's analogy of the Watts steam governor (laid out in detail by Sabrina here). As I tend to (somewhat rudely) reply to complaints of 'I cannot see how this could possibly explain [insert what this person studies here]', your failure of imagination should not be mistaken for a problem for my theory, and it's past time the field started taking the implications of embodiment seriously.

Summary
Embodied cognition is not about letting the body nudge the contents of cognition - it's about treating the body (and the environment, through our embodied perceptual explorations of that environment) as critical elements in a broader cognitive system, and the shape of that system is different from anything we've thought about before in cognitive science. Embracing embodiment is a radical move, but as the evidence continues to roll in now we know what kinds of questions to ask, it's clearly the future of cognitive science.

References
Barrett, L (2011). Beyond the Brain: How Body and Environment Shape Animal and Human Minds. Princeton University Press; New Jersey.

Jostmann, N., Lakens, D., & Schubert, T. (2009). Weight as an Embodiment of Importance Psychological Science, 20 (9), 1169-1174 DOI: 10.1111/j.1467-9280.2009.02426.x Download 

McBeath, M.K., Shaffer, D. M., & Kaiser, M.K. (1995). How baseball outfielders determine where to run to catch fly balls. Science, 268, 569-73. Download


Miles, L., Nind, L., Macrae, C. (2010). Moving Through Time Psychological Science, 21 (2), 222-223 DOI: 10.1177/0956797609359333 Download


Pfeifer, R., and Bongard, J. (2007). How the Body Shapes the Way We Think. MIT Press, Cambridge, Mass.

Pfeifer, R., and Scheier, C. 1999. Understanding Intelligence. MIT Press, Cambridge, Mass.