The Bliss of Motor Abundance

The fundamental question in psychology boils down to "why did that person do that thing they just did?". Welcome to my new favourite example.

Figure 1. I am pretty sure this move totally makes sense

I saw this on Twitter the other day and I couldn't stop watching it. What the ever-loving hell is that cat doing? Then I realised I had a hypothesis, and that it was a fun example of an ecological affordance analysis. So here we are, at last, with a cat-themed blog post. I'll review this manouver, claim that it's all about effecting affordances, and then chat a little about complex actions like this.

The Affordances of Prehistoric Objects

I have a new paper in press at Scientific Reports (Wilson, Zhu, Barham, Stanistreet & Bingham, 2016; see also the slides from my EWEP14 talk) and I am so excited about it I can hardly cope. This project has been the most pure, good-old-fashioned science fun I've had in years and I'm very proud of the result.

Figure 1. Spheroids

The paper is an affordance analysis of some prehistoric objects (spherical rocks called 'spheroids') that were excavated from a cave in South Africa. There are several theories about what the prehistoric humans used these for, but one is that they were projectiles used for hunting. I created a simulation of projectile motion and set the parameters of the simulation using data from the literature on throwing for maximum distance. We then showed that a majority of our sample spheroids were ideally suited for throwing to inflict useful damage to a medium sized prey animal over fairly long distances. Given that we know humans have been anatomically specialising for throwing for millions of years, and given that we know modern humans can perceive the affordance for throwing to a maximum distance and select objects that best fit this affordance, we argue that these simulations provide evidence that these objects were selected to be used as projectiles.

This slightly out-of-left-field project was the result of some good luck, some careful management and the hard work of all my collaborators as we tied this together. The paper stands as an exemplar and proof-of-concept of how a task-dynamical affordance analysis can tell us about the behaviour of prehistoric humans.

Do people really not know what running looks like?

Faster, higher, stronger -
wobbly!

When we run, our arms and legs swing in an alternating rhythm. Your left arm swings back as your left leg swings forward, same with the right. This contralateral rhythm is important for balance; the arms and legs counterbalance each other and help reduce rotation of the torso created by swinging the limbs. 

It turns out, however, that people don't really know this and they draw running incorrectly surprisingly often. Specifically, they often depict people running in a homolateral gait (with arms and legs on the same side swinging in the same direction at the same time; see the Olympics poster). I commented on a piece by Rose Eveleth at the Atlantic about a paper (Meltzoff, 2014) that identifies this surprising confusion in art throughout history and all over the world, and that then reports some simple studies showing that people really don't know what running is supposed to look like.

Rose covered the topic well; I wanted here to critique the paper a little because it's a nice example of some flawed cognitive psychology style thinking. That said, I want to say that I did like this paper. It's that rare thing - a paper by a single author who just happened to notice something and think about it a little then report what he found in case anyone else thought it was cool too. This is a bit old school and I approve entirely.