Rock climbing hacks! (now with added speculation)

I’m going to tell you about an experience that I often have rock-climbing and then I’m going to offer you some speculation as to the cognitive neuroscience behind it. If you rock-climb I’m sure you’ll find my description familiar. If you’re also into cognitive neuroscience perhaps you can tell me if you think my speculation in plausible.

Rock-climbing is a sort of three-dimensional kinaesthetic puzzle. You’re on the side of rock-wall, and you have to go up (or down) by looking around you for somewhere to move your hands or feet. If you can’t see anything then you’re stuck and just have to count the seconds before you run out of strength and fall off. What often happens to me when climbing is that I look as hard as I can for a hold to move my hand up to and I see nothing. Nothing I can easily reach, nothing I can nearly reach and not even anything I might reach if I was just a bit taller or if I jumped. I feel utterly stuck and begin to contemplate the immanent defeat of falling off.

But then I remember to look for new footholds.

Sometimes I’ve already had a go at this and haven’t seen anything promising, but in desperation I move one foot to a new hold, perhaps one that is only an inch or so further up the wall. And this is when something magical happens. Although I am now only able to reach an inch further, I can suddenly see a new hold for my hand, something I’m able to grip firmly and use to pull myself to freedom and triumph (or at least somewhere higher up to get stuck). Even though I looked with all my desperation at the wall above me, this hold remained completely invisible until I moved my foot an inch — what a difference that inch made.

Psychologists have something they call affordances (Gibson, 1977, 1986), which are features of the environment which seem to ‘present themselves’ as available for certain actions. Chairs afford being sat on, hammers afford hitting things with. The term captures an observation that there is something very obviously action-orientated about perception. We don’t just see the world, we see the world full of possibilities. And this means that the affordances in the environment aren’t just there, they are there because we have some potential to act (Stoffregen, 2003). If you are frail and afraid of falling then a handrail will look very different from if you are a skateboarder, or a freerunner. Psychology typically divides the jobs the mind does up into parcels : ‘perception’, (then) ‘decision making’, (then) ‘action’. But if you take the idea of affordances seriously it gives lie to this neat division. Affordances exist because action (the ‘last’ stage) affects perception (the ‘first’ stage). Can we experimentally test this intuition, is there really an effect of action on perception? One good example is Oudejans et al (1996) who asked baseball fielders to judge were a ball would land, either just watching it fall or while running to catch it. A model of the mind that didn’t involve affordances might think that it would be easier to judge where a ball would land if you were standing still; after all, it’s usually easier to do just one thing rather than two. This, however, would be wrong. The fielders were more accurate in their judgements — perceptual predictions basically — when running to catch the ball, in effect when they could use base their judgements on the affordances of the environment produced by their actions, rather than when passively observing the ball.

The connection with my rock-climbing experience is obvious: although I can see the wall ahead, I can only see the holds ahead which are actually within reach. Until I move my foot and bring a hold within range it is effectively invisible to my affordance-biased perception (there’s probably some attentional-narrowing occurring due to anxiety about falling off too, (Pijpers et al, 2006); so perhaps if I had a ladder and a gin and tonic I might be better at spotting potential holds which were out of reach).

There’s another element which I think is relevant to this story. Recently neuroscientists have discovered that the brain deals differently with perceptions occurring near body parts. They call the area around limbs ‘peripersonal space’ (for a review see Rizzolatti & Matelli, 2003). {footnote}. Surprisingly, this space is malleable, according to what we can affect — when we hold tools the area of peripersonal space expands from our hands to encompass the tools too (Maravita et al, 2003). Lots of research has addressed how sensory inputs from different modalities are integrated to construct our brain’s sense of peripersonal space. One delightful result showed that paying visual attention to an area of skin enhanced touch-perception there. The interaction between vision and touch was so strong that providing subjects with a magnifying glass improved their touch perception even more! (Kennett et al, 2001; discussed in Mind Hacks, hack #58). I couldn’t find any direct evidence that unimodal perceptual accuracy is enhanced in peripersonal space compared to just outside it (if you know of any, please let me know), but how’s this for a reasonable speculation — the same mechanisms which create peripersonal space are those which underlie the perception of affordances in our environment. If peripersonal space is defined as an area of cross-modal integration, and is also malleable according to action-possibilities, it isn’t unreasonable to assume that an action-orientated enhancement of perception will occur within this space.

What does this mean for the rock-climber? Well it explains my experience, whereby holds are ‘invisible’ until they are in reach. This suggests some advice to follow next time you are stuck halfway up a climb: You can’t just look with your eyes, you need to ‘look’ with your whole body; only by putting yourself in different positions will the different possibilities for action become clear.

(references and footnote below the fold)

footnote:
My intuition is that this is the area around which we feel ‘an aura’ if someone reaches towards us; this is completely unsubstantiated speculation however

References:

Gibson, J.J. The theory of affordances. In R.E. Shaw and J. Bransford,
eds., Perceiving, Acting, and Knowing, Erlbaum Assoc., Hillsdale. N.J., 1977.

Gibson, J. J. (1986). The ecological approach to visual perception. Lawrence Erlbaum Associates Inc, US.

Kennett, S., Taylor-Clarke, M., & Haggard, P. (2001). Noninformative vision improves the spatial resolution of touch in humans, Current Biology, 11(15), 1188-1191.

Maravita, A., Spence, C., & Driver, J. (2003). Multisensory integration and the body schema: close to hand and within reach, Current Biology, 13(13), 531-539.

Oudejans, R. R., Michaels, C. F., Bakker, F. C., & Dolne, M. A. (1996). The relevance of action in perceiving affordances: perception of catchableness of fly balls., J Exp Psychol Hum Percept Perform, 22(4), 879-91.

Pijpers, J. R. R., Oudejans, R. R. D., Bakker, F. C., & Beek, P. J. (2006). The role of anxiety in perceiving and realizing affordances, Ecological Psychology, 18(3), 131.

Rizzolatti, G., & Matelli, M. (2003). Two different streams form the dorsal visual system: anatomy and functions, Experimental Brain Research, 153(2), 146-157.

Stoffregen, T. A. (2003). Affordances as properties of the animal-environment system, Ecological Psychology, 15(2), 115-134.

Crossposted at mindhacks.com