Gibson and the Learning of Affordances

Let me add a comment on this passage:

"The central question for the theory of affordances is not whether they exist and are real but whether information is available in ambient light for perceiving them. The skeptic may now be convinced that there is information in light for some properties of a surface but not for such a property as being good to eat. The taste of a thing, he will say, is not specified by light; you can see its form and color and texture but not its palatability; you have to taste it for that."
Gibson, 1979, p.140-141

Andrew, Gary, and Gennady have each proposed that Gibson could handle exploding box cases by appeal to learning.  (Now, this won't work, since your learning is not going to change the ability of a typical affordance to structure light.  The problem is that surfaces are on the outside of objects, but what makes for the typical affordance is on the inside of the object, so the light can reach to affordance to be structured by it.)   And, they are right that Gibson does mention learning about affordances. But, notice that, following this passage, Gibson might well just admit that the palatability of a thing is not specified by light and that you have to learn whether an object affords palatability by tasting it, then .....?  Instead, he presses on with the view that higher-order invariants in light are going to save the day.  So, in what follows in this passage, he is more willing to stay the course in saying that affordances are specified by light than have been Andrew, Gary and Gennady.  But, then again, Gibson apparently didn't consider anything exactly like the exploding box protocol.  So, it seems to me that Gibson is somewhat equivocal regarding how he might handle such cases. 

Is this Table Meaningless?

Maybe Andrew should take TSRM to task for this meaningless list of "affordances".

TSRM and Exploding-Box-Like Cases

In comments a couple of posts back, Andrew has claimed that the exploding box type cases have a pretty marginal significance for EP.   Setting aside for a moment whether those type cases work, here is how I see it being sort of important for TSRM at least.  (Yesterday was why it should matter to Gibson.)

What these cases bear on is the idea that there is lawful specification of affordance by an optical property.

Thus we have two laws relating properties: 'o-ness -> c-ness' (between occurrent property and affordance) and 'e-ness -> o-ness' (between optical property and occurrent environmental property). By transitivity we have: 'e-ness -> c-ness'. That is, there is a lawful specification of an affordance by an optical property. In sum, there is a legitimate construal of dispositions and of natural law that, in principle, allows affordances to be optically specified, thus denying (on grounds separate from those identified in Section 4) Fodor and Pylyshyn their argument against the direct perception of ecologically-significant properties. Recall that Fodor and Pylyshyn admit quite cheerfully in the conclusion of their Section 4 that if there were laws about ecological kinds then there could be direct detection of ecological kinds. (TSRM, 1981, p. 266).

So, I'm pursuing (in my blogolife), though I do not yet claim to have, an objection that goes pretty close to the heart of the TSRM paper.  I'm challenging the idea that there is a lawful specification of affordances by optical properties.  The argument might not work, but I'm not just firing random shots in the air.

TSRM's Shark Example 7

In the niche of the shark 'an edible thing' and 'electric field of, say, type F' are nomically related. To predicate of the shark (a) 'detects electric field of type F' and (b) 'takes to be an edible thing' is not to refer to two different states of affairs, one (viz. (b)) that is reached from the other (viz. (a)) by an inference.  (Turvey, Shaw, Reed, and Mace, 1981).

It looks like TSRM think that sharks find food by detecting the electrical fields of fish, but here is what Andrew says they say:

Turvey, Shaw, Reed & Mace (1981)

But Gibson is not denying that information is rooted in physics; he's simply pointing out that the correct level of analysis for the information available to a perceiving organism is ecological. What an organism needs to know is not how far away something is, but whether it can reach that thing - in other words, affordances. You can't get to affordances via the objects of physics, because affordances are personal and contain meaning while physics is neither of these. You therefore have to get to affordances by detecting information about affordances, not units of physics.  (italics added, ref here.)

Here, it looks like Andrew is saying that TSRM think that sharks can't find food (an affordance, right?) by detecting an electric field (a "unit" of physics).  [Actually, this passage seems equivocal to me.  There's the part in the first sentence about Gibson not denying that information is rooted in physics.]

But, then, Andrew also writes this (ref here),

Enter Turvey, Shaw, Reed and Mace. Their reply to F&P is simple: Gibsonian information is suitably constrained (i.e. you can’t just claim any old property can be perceived) and that these constraints are not simply ad hoc, but rooted firmly in a consideration of the physics of the world in which vision evolved. This paper is elegant and clear; in fact its elegance and clarity manage to retrospectively make F&P’s paper worthwhile because it caused Turvey et al to write this.

The constraints lie in the existence of ecological laws. A law describes a set of conditions and the necessary consequence of those conditions (if the temperature of pure water at sea level is 100°C then the water will boil). Laws have scope: the scope is laid out in the set of conditions. Within that scope, the conclusion is necessary, i.e. if the conditions obtain and the scope is correct the conclusion must be the case. Ecological laws lay out the conditions and consequences by which a pattern in (for example) an optic array can specify an object or event in the world; these conditions must relate to the physics of the situation (so ‘shoeness’ is not the kind of property we are dealing with).(italics added)

Now, one must relate organisms to the physics.

So, it looks like there a real dilemma here.  On the one hand, Andrew wants physics ontology to be incommensurable with perceptual ontology, perhaps so that psychology is apparently not reducible to physics.  On the other hand, Andrew wants physics to be commensurable with psychology, so that he can resist the Fodor and Pylyhshyn "trivialization argument".   This seems to me not a mere slip in wording, but the product of distinct theoretical demands.  There are two things, neither of which an EPist, like Andrew, seems to want to abandon. 

Personally, I would think the thing to do is abandon the incommensurability thing.  But, of course, the really big thing to do would be to give up on EP.

The Shark Cognitivist-Style

In the spirit of the best defense being a good offense, in my other posts on the TSRM account of the shark, Andrew has been hounding me for a mechanistic cognitivist account of what is going on with the shark. I've been avoiding this as I hate to get off topic, but here's a post to reply to Andrew's challenge/question.

It seems to me that there is a mechanistic cognitivist account of the shark implicit in TSRM's account.  The idea is that the shark detects the electric field F, then infers (perhaps on the basis of an implicit assumption that if there is an electric field F, then there is probably something edible) that there is something edible.  By cognitivist lights, inference can be mechanistic, since inference is the kind of thing a computer can do and computers are mechanistic devices.  This is the account TSRM are evidently trying to forestall in the following passage:

To predicate of the shark (a) 'detects electric field of type F' and (b) 'takes to be an edible thing' is not to refer to two different states of affairs, one (viz. (b)) that is reached from the other (viz. (a)) by an inference. Rather, it is to make reference in two ways to a single state of affairs of the shark-niche system.

So, here is what seems to me to be the lay of the land.  It seems to be common ground to both cognitivists and TSRM that the shark detects the electric field F.  Then, the issue that separates them is how this detection relates to taking there to be a fish present.  The cognitivist answer is that the detection of the field and taking there to be a fish present are related by inference; one is among the premises for a conclusion of the latter.  The TSRM answer is that the detection of the field and taking there to be a fish present are identical.

What I have been challenging is the adequacy of the TSRM account.

Andrew won't like the cognitivist answer, but that's not the same as claiming that I don't have one or that there isn't one.

Rush Hour Revisited 2

Second, suppose that you are playing a visual problem-solving game, such as Rush Hour, or completing a jigsaw puzzle.

Here is, perhaps, a simpler way to get to my point.  Suppose that problem solving is a behavior.  Then, one might have extended behavior without extended cognition.  Cognitive processes are one thing; behavior another.  Cognitive processes contribute to cognitive behavior is the idea.  That's what I take to be the standard cognitivist line.  (Somewhere Chomsky says something like "linguistic behavior is the product of linguistic competence, along with poorly understood factors such as attention, set, etc."  I'm thinking this appeared in Chomsky's Language and Mind, or earlier.)  What muddies the water, perhaps, is the idea that problem solving is properly described as cognitive behavior.  But, why is it cognitive behavior?  Because it includes a cognitive process in the brain of course.

So, I see this appeal to problem solving inconclusive.

Moreover, I think that essentially the same story can be told about Gary Williams example of decision making in sortilege.

So, Gibson's not *that* dismissive

Gibson writes,

I am also asking the reader to suppose that the concept of space has nothing to do with perception. Geometrical space is a pure abstraction. . . . Space is a myth, a ghost, a fiction for geometers. (Gibson, 1979, p. 3).

Ok.  Now that seems pretty dismissive of geometry to me, but I think that Andrew and Gary are probably right that this is a bit hyperbolic.  Gibson apparently does not want to go so far as to not use geometry in his scientific thinking.  After all, it looks as though he implicitly needs at least some geometry, and maybe even some Euclidean geometry (but not necessarily Cartesian co-ordinates), to determine how the ambient optic array changes when a person goes from sitting to standing.

From Gibson, 1979, p. Figure 5.4.

Empirical Psychologists vs Armchair Philosophers 2

Some weeks ago in this post at his blog, Andrew was complaining about philosophers threatening to be irrelevant with their out-of-this world thought experiments and imaginary scenarios and the like.  So, being the small-minded person that I am, I'm pleased to find Runeson, of whom Andrew appears to have a decent opinion, has borrowed to some degree from philosophical work.

In a philosophical analysis of the information in signals, Dretske (1981) is explicit on this:

The fact that we can imagine circumstances in which a signal would be equivocal, the fact that we can imagine possibilities that a signal does not eliminate, does not, by itself, show that the signal is equivocal .... To qualify as a relevant possibility, one that actually affects the equivocation of (and therefore information in) a signal, the possibility envisaged must actually be realizable in the nuts and bolts of the particular system in question. (p. 131) (Runeson, 1988, p. 298)

In truth, I think that this relevant alternatives idea might have begun with an Oxford don, J.L. Austin, a chap who was, I think, not very much interested in science.

J. L. Austin, Runeson's Hero?

As an essentially irrelevant aside, my frequent partner in crime, Fred Adams is a Dretske student.  (He's even mentioned in the front matter of Knowledge and the Flow.)

Tomorrow I'll try to get back to some serious posts on Runeson.

Andrew Wilson's "Book Review" Post on The Bounds of Cognition

Andrew has a lengthy post on Bounds here at "Notes from Two Scientific Psychologists". The discussion proceeds within the context of a Gibsonian approach to perception.

Empirical Psychologists vs Armchair Philosophers 1

Some weeks ago in this post at his blog, Andrew was complaining about philosophers threatening to be irrelevant with their out-of-this world thought experiments and imaginary scenarios and the like.  So, being the small-minded person that I am, I'm pleased to find Runeson, of whom Andrew appears to have a decent opinion, has a somewhat less hostile take on out-of-this-world thought experiments

In the ecological perspective an interesting empirical problem follows: How would we fare perceptually if we were placed in a world that was less constrained-for instance, one in which some of the above constraints on room shape were relaxed? An Ames' room viewed from noncanonical points would instantiate such a condition. Those (as yet unspecified) motion-independent invariants whose validity is conditional on normal shape constraints would be specifying the wrong spatial layout. To the extent that those invariants remained perceptually relied upon, the perceiver would be in trouble. Could perceptual leaming effect reliance on only the types of information that remain fully valid (motion perspective, binocular disparity, fine texture gradients, etc.)? If it could, how efficiently, comfortably, and confidently the perceiver could function in that environment appears an open question of both theoretical and applied relevance. (Runeson, 1988, p.302).

What if we lived in a world with different laws of physics?  When is that going to happen?  Yet, such a scenario is one that might have theoretical and applied relevance?  Would Andrew have a (spherical) cow thinking about these questions? =)

Maybe the divide here is not between philosophers and psychologists (as Andrew seems to suggest), but those who are and who are not open to hypothetical reasoning.

I had forgotten about this study

In recent discussions of aperture vision, Gary appears to have been articulating a view according to which studying aperture vision is not doing ecological psychology.

He writes,"So Gibson would respond to Ken by saying that in the aperture experiment, there is mere sensation going on, but no perception, because perception is defined as the discrimination of meaningful ecological information and there is none available in the ambiguity of the aperture experiment."

But, there is this study:

The Distorted Room Illusion, Equivalent Configurations,
and the Specificity of Static Optic Arrays

Sverker Runeson
Uppsala University, Uppsala, Sweden

The distorted room illusion (DRI) and the attendant argument for perceptual ambiguity is critically analyzed from a Gibsonian/ecological point of view. The notions of multiple specification, conflicting information, and perceptual skill are invoked in showing how the ecological approach can accommodate illusion effects that may remain under mobile binocular viewing conditions. Static optic arrays are shown not to be ambiguous. So-called equivalent configurations
are found to be analytic artifacts, appearing when the problem of information is treated in geometrical terms without regard for constraints due to physical and ecological regularities. The relative importance of motion-based and motion-independent information is discussed.

Journal of Experimental Psychology: Human Perception and Performance 1988, Vol. 14, No. 2, 295-304

What's the "trick" here?

In some comments over at "Notes from Two Scientific Psychologists" here and here, I have been wondering about the Gibsonian claim that "Only the eye considered as a fixed camera can be deceived. The actual binocular visual  system cannot. (Gibson, 1979, p. 281)"  and that "all illusions are tricks".  I am curious about the snake illusion and certain auditory illusions.  What's the trick in these cases?

But certain cases of amodal completion raise the same problem.  The illusion is that some occluded object looks circular, when it is not.  What's the "trick" in these cases?

Now, I know that Gibsonians often worry about 2D drawn illusions, but at least some of the problematic amodal completion cases seem not to depend on the 2D character of the illusion.  Readers can verify this for themselves by creating circular "tiles" with parts cut out and see for themselves.  

Seeing, however, as I learned how to use Windows Moviemaker for my appearance on Philosophy TV, I thought I would venture to add some video showing the "tile" I made.  The video is not meant to replace doing the demo for one's self, but it was fun for me to make. How many philosophers add video to their blogs?  (It's a good thing I'm not dreaming of going to film school, but that's another matter.)