Sunday, 26 February 2017

Evidence for the Kinematic Specification of Dynamics

Gibson’s most detailed analysis of the KSD problem came from work on the perception of dynamic occlusion (viewing one surface become progressively hidden behind another as they move; Gibson, Kaplan, Reynolds & Wheeler, 1969; Kaplan, 1969). As one surface goes behind another, the sensations coming from the rear surface stop hitting the retina; they disappear. However, was is perceived is the progressive occlusion of a persisting surface; it is not disappearing, it is going out of view. Gibson and his students identified the kinematic pattern of transformation of the optic array that was specific to occlusion and distinguished it from the pattern specific to a surface actually going out of existence. In the former case, optical texture from the rear surface is progressively deleted over time from the optic array at an edge as it goes in behind the closer surface, and that texture progressively accretes as it comes back into view. In the latter case, there are a variety of transformations depending on how the surface is disappearing (melting vs being eaten, etc). Each event creates a specific optical pattern, but these patterns are not identical to the underlying dynamics. Observers, however, readily and easily perceive and report the underlying dynamics, not the optical patterns. Additional evidence that people are perceiving the dynamics comes from work in multiple object tracking (Scholl & Pylyshyn, 1999). People can track multiple moving targets over time, and can continue to do so even if the objects move in and out of view, but only if they do so in an occlusion event. If the objects go out of view by imploding, tracking goes to chance. In the occlusion case, the visual attention system continues to perceive a persisting object and can often pick it back up when it returns to view. In the imploding case, this system perceives that the object has ceased to exist, and it no longer tracks it. 

Saturday, 18 February 2017

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.

The Ecological Approach - The Accidental Textbook

Over the years this blog has collected 232 posts on a wide range of topics and we have multiple papers out and forthcoming working on the ecological approach to psychology and the behavioural sciences more generally. On the plus side, I have material all over on a wide range of topics; on the down side, I have material all over on a wide range of topics and it's hard sometimes to hand someone a useful entry point. 

I always figured we would accidentally write a textbook on this blog and while we aren't there yet, we are working on a fairly comprehensive paper that tries to walk through the entire approach. Over the next few weeks, I'm going to post some excerpts from that work to a) have some focused information in the them and b) get some feedback about whether it makes sense.


At this point, I assume you are sufficiently intrigued by the ecological approach that you would like to know how it works. One motivation for getting to that point is the fact it allows mechanistic models of psychological phenomena; another may be a desire to be more embodied or enactive in your science. I'm not going to work on convincing you at the moment; I'm just going to try out the clearest explanations of all the key ideas I currently have in order to educate and get feedback. 


I will come back and update this post with links to all future posts on this topic, in order (you can also search with this tag). If by any chance you are finding this material useful, drop me a line and let me know. 

Textbook Posts

Friday, 16 December 2016

Affordances are Not Relations, Part 1: Chemero (2009)

Affordances are on my mind right now as I develop the throwing research programme, and a major commitment of that work is that affordances are (dispositional) properties of the environment picked out by organisms in the context of tasks. This commitment has become important enough that it's time to get into developing specific arguments against the various 'affordances are relations' papers that are out there. I am working towards a paper summarising my objections to the relations account that also strongly advocates for the properties account on the grounds it enables a lot more science. This will be an occasional series of posts as I read and draft my arguments; as always, feedback welcome.

In this first post, I want to draft a response to 'Affordances 2.0', from Chemero's (2009) book Radical Embodied Cognitive Science. I previously blogged this chapter in two parts here and here

Saturday, 10 December 2016

The Affordances of Natural vs Designed Environments (A Purple Peril)

I had a conversation with Eric Brymer (@Ericbrymer) a few weeks ago. Eric is a Reader at Leeds Beckett and is an ecologically minded psychologist interested in the effects of the natural world on mental health. We chatted affordances for a while, and despite it being a very interesting chat, I really wasn’t sure if I had anything to say about the differences between the natural and designed worlds. 

But I have not been able to stop thinking about this topic, and now I think there’s something fairly cool here.

Saturday, 3 December 2016

Is the Ecological Approach Radical Enough?

Radical enactivists do not just want to get representations out of their explanations for our mental life. They also want to get rid of the notion of content. Hutto & Myin (2013) is the strong version of this claim. 

Mental states or processes have content if there are specified conditions of satisfaction and if it can be evaluated for things like truth (i.e. does the thing conveying content doing so accurately or not?). Part of the concern is that ecological psychology is committed to content and thus can’t play with the other radical theories. The evidence is that we talk about things like ‘information about affordances’; that ‘about’ implies content. 

van Dijk, Withagen & Bongers (2015) took a swing at defending a content-less ecological psychology. I admire the attempt to get the radical camps on the same page, but at the end of the day I think a) the defence is grounded on the wrong notion of affordances (as relations, instead of dispositions) which means b) I don’t think it works but that c) I don’t think I care. I am as yet unfazed by critiques of content, although I’m happy to hear more on this; frankly Hutto & Myin’s book is a real struggle to read and any clarity people can add, I’ll take. 

Friday, 2 December 2016

Scarantino (2003) “Affordances Explained”

Turvey, Shaw, Reed and Mace (1981) laid out an ontology of affordances; a formal account of the kind of things they are. They described them as dispositions, properties of the world constituted by sets of anchoring properties that offered an action to an organism whose dispositions could complement the affordance. Making affordances dispositions makes them real, makes them pre-date the interaction with the organism, and accounts for their odd ‘not doing anything until interacted with’ kind of existence. I am firmly Team Affordances are Dispositions and I have yet to meet an alternative account that supports a science of affordances or even allows them to be perceived.

The literature on dispositions was somewhat limited in 1981, but in 1998 Stephan Mumford published the definitive work on what they are and how they work. I always hoped someone with the necessary philosophy chops would use this work to strengthen the foundations of affordances (I even almost talked a philosopher into doing it!) but it turns out I’m covered. Andrea Scarantino (2003) published ‘Affordances Explained’ and did much of the necessary work, and there are some very useful things in the analysis. This post is me working through this material, translating from the technical philosophy into words I can understand better.