Thursday, February 10, 2011

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. 


  1. Palatability does stick out, it's true - he does not follow it up there. But that section isn't really about learning, it's about optical specification (hence his 'pressing on' there).

  2. Right. He *could* have at this point tried to appeal to learning, but he did not. Note, however, that at the bottom of p. 142, Gibson does have this footnote:
    If the affordances of a thing are perceived correctly, we say that it looks like what it is. But we must, of course, learn to see what things really are-for example, that the innocent-looking leaf is really a nettle or that the helpful-sounding politician is really a demagogue. And this can be very difficult.

    So, learning is not that far from his mind.