Tuesday 4 May 2010

Reading Group - Heft (2001) on Gibson

Part II of Heft moves on from James and Holt and into Gibson's ecological approach. The point of Part I, as I've discussed, was to establish the roots of Gibson in the radical empiricism of James, conveyed via the molar behaviourism of Holt. Part II is a detailed discussion of the ecological approach, specifically that laid out in Gibson (1979). I'm therefore going to leave the details of the exposition to the other reading group posts, and focus on the higher level connections and points Heft makes. I'm also going to handle Chapter 3 in two posts: this one will be a brief summary of some key points, and later this week I'll reveal how I've been mistaken about affordances for quite a while.

James' radical empiricism offered a lot in the way of solutions for the key problems of psychology, but it was lacking several key elements. Gibson is, at one level, going to offer a radical empiricist account of perception, including the key mechanism of information. This account will arise from Gibson's basic perspective as a behaviourist (a dirty word in modern psychology, and often considered to be a reason one can safely ignore Gibson's theories) - Gibson rejects mentalism in all its forms, and aims to identify predictable (i.e. stable) functional relations between an environment and the behaviour of an organism. His behaviourism is molar and purposive, the result of learning from Holt (who also taught Tolman).

Heft identifies two central claims that Gibson will develop, and four theoretical elements to support these claims. These derive at least in part from the fact that Gibson has a strong phenomenological streak to his work; he pays deep attention to the actual contents of experience and attempts to address these rigourously. While Gibson thought of himself as a behaviourist, Heft identifies that there is no clear conflict between these two stances and highlights the work of Merleu-Ponty as the 'flavour' of phenomenology most closely aligned with Gibson.

Claim 1: The relation between organism and environment is best considered as a mutuality and a reciprocity
Organisms and their environments imply one another, in a mutuality. The standard account separates these, and describes each of them separately (in terms of physics and physiology). Gibson points out that this analysis simply misses too much vital information: while you can, for example, describe a reach-to-grasp action per se, reach-to-grasp actions only ever occur in context. The psychological expression of the reach-to-grasp action is always with respect to an environmental referent: you do not reach, you reach for something, and the specific reaching action that is produced is co-determined by the biomechanics of the hand and arm in relation to object properties (e.g. size, distance, etc).

This relation is dynamic, and reciprocal. Organisms and their environment stand in a special relation to one another (different from the relations between say, an inanimate object and it's surroundings); this relation evolves over time and is altered by both the organism and the environment. For example, the simple act of locomotion alters the point of observation, possibly in response to one object in the environment occluding another, more interesting object. This special, reciprocal relationship will be formalised in Gibson's ecological optics.

Claim 2: Ecological phenomena are to be found at an intermediate scale of time and space
Physics describes objects and events whose scale varies from the very small (quantum) to the very large, and from the very slow (the evolution of stars) to the very fast (relativistic events). These are entirely the wrong sorts of things to be concerned about when considering the experience of medium sized, slow-ish organisms; we have a good sense of what a day means, or a month, or a year, but not a century, or a millennium. Frank Herbert, in God Emperor Dune, has the 3,500 year old Leto II discussing how his altered life-span has provided him with a perspective on time and change that ordinary humans simply do not have. The scale of things matters; but more on this from Heft later.

Four Key Contributions
1. Optical flow
Optical flow is the term Gibson gave to the way environmental features (texture elements) stream in and our of view as an organism moves around. It is the clearest example of the relational character of psychology, because the flow is shaped by both the environment and the organism. It is also where Gibson begins to lay out his functional analysis of purposive behaviour: organisms plan their actions so as to produce specific changes in the optical flow, not to engage specific muscles or limbs. Action is organised around the higher-order goal of, e.g. enlarging a region of flow by approaching it. Think again about Holt's description of the man walking past the window - the man is doing that at that time because of the action he is engaged in, namely 'going-to-the-theatre-to-review-the-play-there'.

2. Egomotion
The location of the self in experience is a time honoured philosophical problem: Gibson's solution is to point out that the self is specified at all times in visual experience. Flow is defined at all times with respect to a point of observation, and there is also visual information about the self always available (occlusion by your nose and head, your arms and legs coming in and out of view, etc). Information specifying the world is always accompanied by information specifying the self, and vice versa.

3. Occluding edges
Gibson pays attention to the actual contents of experience (his phenomenological bent) and he notices one key feature of optical flow. When one object passes behind another, it is not seen to simply cease to exist, and optically, this is supported by a progressive deletion of optical texture elements. When an object behind another is revealed (by it moving or the organism; remember these are mutual and reciprocal) there is now a progressive accretion of optical texture elements. In other words, objects are seen to persist as they come in and out of view; they do not simply vanish (an event which is specified by an entirely different pattern of optical flow). Perception, therefore, does not simply occur on the knife edge of the present; it extends from the present into both the past and the future to a small degree, supported by perceptual information (properly conceived). This provides a mechanism for this Jamesian notion.

4. Affordances
An affordance is the perceived functional significance of an object, event or place for an individual. They are not a relation between organism and environment, although they are typically composed of relations between things in the environment. They exist independent of an observer, but are not merely 'primary' or 'objective' qualities; they contain meaning for an individual, but they are not merely 'secondary' or 'subjective' qualities. They are, in fact, entirely outside the Cartesian framework we are so used to dealing in, and are therefore metaphysically a bit weird.

I'm going to go into this in more detail in the next few posts. There's a huge amount of material here: capturing Gibson's characterisation and coming to terms with it, not to mention the extra-ordinary level of in-fighting these things have created. Briefly, whether or not affordances are relations or dispositions has effectively split the ecological camp, and both sides claim Gibson as their champion. Reading up on this debate is what got me back into thinking about these things and then blogging about them; so I can safely say we will visit these again, a lot.


  1. Rather unrelated to the post (which I need more time to digest), but I wanted to ask about the perceived rarity of ecological psychologists. In earlier posts, you implied that you were part of some shadowy underbelly of psychology, and for every 1 of you there are 10 old-school representation style types. But that just has not been my perception of things. Certainly, in the world of object lifting where the majority of my work takes place, many of the big players are Turvey offshoots, and pretty ecological minded. Even in perception/action in general people love in invoke affordances as easy introductions into tool use and the like. I would certainly say that well over half my lab has overt ecological leanings. And sure, while this really only applies to the perception/action crowd with which I associate, I'm not sure there is any need for non motor control researchers to care (if their tasks are not within the ecological framework, but still being completed successfully by the subject, then their tasks are outwith the mandate of this debate. Whether we should care about their results, however, is another matter.) Basically, my question is whether ecological psychology is all that rare? These ideas have an (albeit largely bananas) dedicated journal, and a well funded set of researchers (given that many many many still consider movement to be a niche field), at least in north america. Discuss.

  2. Coming from a completely different area of psychology, I can tell you that ecological psychologists are extremely rare in, say, the study of language, memory, emotion, categorisation, and most any type of imaging or social psych research. When ecological approaches are mentioned, they tend to be misinterpretations of embodied cognition (e.g., all of the body/cognition response compatibility research).
    I think you correctly identify ecological psych as a niche field, in that it's treated as a thing to study, rather than a general approach to any psychological question. For most fields, the general approach is dominated by an information-processing perspective, even if this is not explicitly representational.

  3. Are we rare? Yes: there is still a perception literature, distinct from a motor control literature. These guys never talk to each other, and always (almost always?) invoke representational accounts. People who explicitly study perceptually guided actions will have at least encountered Gibson and the ideas, so you have a biased sample, but even most of these still have a computational/representational core.

    But most importantly, I think I'd like to draw a distinction between people who use the word affordance, and those who understand what it entails.