Affordance Maps and the Geometry of Solution Spaces

I study throwing for two basic reasons. One, it is intrinsically fascinating and I want to know how it works. Second, it's become a rich domain in which to study affordances, and it is really forcing me to engage in great detail with the specifics of what these are.

My approach to affordances is that they are dynamical properties of tasks, which means that in order to study them, I need to be able to characterise my task dynamics in great detail. I developed an analysis (Wilson et al, 2016) to do this, and I also have a hunch this analysis will fit perfectly with the motor abundance analyses like UCM (Wilson, Zhu & Bingham, in press). I have recently discovered that another research group (led by Dagmar Sternad) has been doing this whole package for a few years, which is exciting news. Here I just want to briefly summarise the analysis and what the future might hold for this work.

The Nature of Ecological Perceptual Information

The central issue in the perception of the world is how the perceptual system comes into contact with that world. In vision, the assumption for centuries has been that the experienced world must be recovered somehow from the 2D image of the world projected onto the retina by the lens of the eye. Scientists therefore hunted for patterns on the retina that preserved critical structure from the world by copying some part of that critical structure. 

James J Gibson was, for a long time, no exception to this hunt. His early empirical work (grounded in the theory he laid out in The Perception of the Visual World; Gibson, 1950) created and manipulated retinal images that, for example, contained gradients of optical texture that matched gradients of physical texture created as surfaces receded in depth, or changed their shape or orientation relative to a point of observation. But time and again, Gibson found that perceptual experience was not any straight-forward function of retinal stimulation (i.e. sensations). People did not ‘see’ what was on the retina (Reed, 1988). The most powerful demonstration of this fact is Gibson’s analysis of dynamic occlusion (Gibson, Kaplan, Reynolds & Wheeler, 1969; Kaplan, 1969) to which we will return below.
Gibson’s later career was defined by the search for an explanation of how perception could be possible if it wasn’t based on sensations and retinal images. Gibson’s solution was his theory of the ecological information available for visual perception published in The Ecological Approach to Visual Perception (Gibson, 1979). 

What follows is a description of ecological information with reference to some of Gibson’s work and the extensive research literature that has taken place since Gibson’s death in 1979. The focus will be on the information in light for vision, because that has been the focus of the research. However, the principles hold for all the various energy media our perceptual systems interact with, and we will review this briefer evidence as well.

Tasks from the First Person Perspective (A Purple Peril)

The great snare of the psychologist is the confusion of his own standpoint with that of the mental fact about which he is making his report. I shall hereafter call this the ‘psychologist’s fallacy’ par excellence.

William James, The Principles of Psychology

This is a video of a baby trying bacon for the first time. The baby gets really really excited, and everyone around him goes 'Ha! Babies love bacon as much as the rest of us, this is great!'. And everyone laughs and cheers.

Except here's the thing. I think what this baby really likes is making his loved ones laugh and cheer. The bacon is fine, but I don't think it's the magical experience his parents assume. They are making the psychologist's fallacy: mistaking what you think is going on for what the person is actually experiencing. (It's our fallacy because our subject matter makes us uniquely susceptible.)

When people come into our labs to take part in experiments, we present them with a situation that we have designed to elicit a specific behaviour from them, and that we manipulate in various ways in order to probe the makeup of that behaviour. We therefore think we know what the person is doing: they are doing the thing we asked them to do. However, this isn't necessarily true, and in order to figure out what our participants did and why, we need to consider how they experienced the experiment. In effect, doing our science right means taking the first person perspective of our participants when we formulate our explanations. 

I take this idea primarily from Louise Barrett's excellent book, Beyond the Brain: How Body & Environment Shape Animal and Human Minds (which I reviewed here). The first couple of chapters spend a lot of time talking about anthropomorphism, and why it's a problem. To be honest, when I read the book I didn't quite know why Louise started with this. But over time, I've realised what an extraordinarily powerful point it is and we now talk about all the time. 

Peril Proposal: The psychologist's fallacy is real, but the ecological approach to understanding task dynamics and the information they create offers a useful framework for avoiding it while we science.