Sunday, 15 April 2012

Shared neural resources for throwing and language: a whacky idea for an experiment

For some time now, there has been an hypothesis floating around in evolutionary biology that the human capacity for language emerged, in part, from the development of our ability to throw long distances with high speed and accuracy. There are a few reasons to think this, mostly correlational, inferential kinds of reasons, but they are accumulating.

We were chatting one day about how to test this hypothesis a bit more directly, and we came up with a whacky experiment. We'd like advice from neuroscientists with experience in brain stimulation techniques about whether this sort of thing is feasible. We'd also like to brainstorm the logic of this experiment and see if we can come up with a practical design that stands a chance of finding something. We then need collaborators; I can handle the throwing side (analysis, measurement, etc) but we don't know anything about TMS and would need an expert on board.

There are many other reasons why this might fail, though - I still need to do a detailed lit review on the throwing/language references I have. Our main problem is that we don't know the kind of obvious difficulties in doing TMS in this kind of context. We'd like to assemble a) an experiment and b) a research team to do the experiment if we can get it to make sense, and if it works we will submit the hell out of this to Nature :)

Friday, 13 April 2012







An invitation

Sunday, 1 April 2012

Did language emerge from the neural systems supporting aimed throwing?

This post was chosen as an Editor's Selection for ResearchBlogging.orgAimed throwing is surprisingly uncommon in the animal kingdom. Humans do it par excellence, and otherwise it only shows up occasionally, even in our closest relatives. Chimpanzees will throw things (often faeces) but unlike humans don't throw things when hunting or trying to get food; when non-human animals throw things, it's usually part of a social encounter.

Throwing is a fascinating task for many reasons; I hope to blog some about the perception-action aspects of this task in the future as I prepare a couple of papers on the topic with my colleagues Qin Zhu and Geoff Bingham (who have previously done some excellent work on throwing to a maximum distance and the size-weight illusion; various papers available here). There are many fascinating questions about the perception of the affordances of throwing and distances to targets which we're starting to tackle empirically.
Biomechanically, throwing an object accurately over any distance requires the precise transmission of force from the large trunk muscles along a kinetic chain formed by the segments of the arm. The large trunk muscles generate forces the arm cannot, and this force is then transmitted by the motion of the arm; each segment weighs progressively less and so the force accelerates each one faster than the last. The end result is a hand moving at high speed. This requires careful timing; if the motion of the segments aren't coordinated carefully you will waste energy moving the limbs in ways that aren't helping the throw.

There has been some speculation for a while now that the neural mechanisms that help support this fine tuned coordination and control for throwing might also be just the kind of resources that could support the development of spoken language. Speech is a complex action that requires exquisite control over the coordination and timing of numerous elements, just like throwing. One hypothesis is that our ancestors began to develop the ability to throw long distances (this being favoured by natural selection processes because it enabled us to hunt and kill huge prey with much less physical risk to ourselves; e.g. Calvin, 1983). Evolution selected for neural resources that supported this activity, and this then opened the door to the possibility of complex spoken language. So do we speak the way we do because we throw the way we do?