What Gibson Isn’t Missing After All: A Reply to Heil

STEPHEN WILCOX AND STUART KATZ

Sometimes it seems as if the advocates of J. J . Gibson’s ideas are in danger of being drowned out by a chorus repeating the same refrain: “Gibson’s theory is incomplete”, The most frequent allegation is that Gibson, although providing insight into the environmental support for perception, fails to account for the internal processes which make it up (e.g., Johansson, 1970; Hamlyn, 1977; Neisser, 1977; Epstein, 1977; Haber, 1980). It is of course, true that Gibson never gave an account of these alleged processes, but that is because, as Reed and Jones (1978) recently pointed out, there are none for Gibson.

Gibson’s theory is only incomplete from the standpoint of more traditional theories. Gibson’s critics have consistently failed to recognize that Gibson begins with a fundamentally different epistemology. They keep trying to analyze Gibson’s position as if were a variation on the Cartesian epistemology which underlies their own theories.

This debate is reminiscent of those that, according to Duhem (1954), have flared up every few centuries in the physical sciences. As he puts it,

. . .each cosmological school admits in its explanations certain properties of matter which the next school refuses to take as real, for the latter regards them as mere words designating more deeply hidden realities without revealing them; it groups them, in short, with the occult qualities created in so much profusion by scholasticism (pp. 14- 15).

For the traditional perceptual psychologist unconscious mental activities are phenomena to be accounted for. For the Gibsonian these entities are creations of the psychologist’s imagination, the unfortunate consequences of a flawed epistemology.

John Heil(1980) has now added a new dimension to the controversy. He begins by granting the point made by Reed and Jones (1978), namely that Gibson’s theory does not require internal processes to bridge the gap between sensation and perception, because for Gibson no such gap exists. Heil goes on, however, to argue that Gibson’s theory is incomplete in a different way. As Heil (1980, p . 268) puts it “. . . the theory is incomplete in the sense that it says nothing at all - or at any rate

J . Theory SOC. Behaviour 11, 3 . Pnittedin Great Britain

3 14 very little - about the basis of the differences in our capacities to see what is there to be seen”.

The purpose of this note is to argue that Heil is incorrect because he is confused in his use of the word basis. Heil seems to think that it is obvious what would constitute such a basis, for he simply states Gibson’s supposed failure as a fact which does not require elaboration. The issue is far from obvious, however. In fact, we will show that Heil has been led astray by his own preconceptions concerning what it means to provide an account of the “basis of the differences in our capacities to see what is there to be seen.”

Let us introduce an analogy. We know that there are wide differences in the characteristics of automobiles. For example, some use less fuel than others. What is the basis of these differences? The answer could take any of a number of forms depending upon the context in which the question was asked. Relevant considerations include the nature of the information available, the sophistication of the person who asks the question, and, perhaps most of all, the purpose for which the question is asked.

One answer is that the differences are due to internal properties of automobiles such as the cylinder displacements and the gear ratios (e.g., four cylinder cars tend to use less fuel than eight cylinder cars). Let us call this a mechanistic explanation. Another answer is that different automobiles have been designed in response to different constraints (e.g., European cars are more fuel efficient, because fuel costs more in Europe). This we will call an evolutiona7y explanation. Likewise we might focus upon the events of an automobile’s life (e.g., cars which have been properly maintained are usually more fuel efficient than those that are not). Let us call this a developmentalexplanation. Or we could point to the purpose for which the automobile was made (e.g., racing cars use more fuel than street cars). This we will call an intentional explanation. Finally, we could simply single out certain observable characteristics (e.g.. bigger cars tend to get poorer mileage). We will refer to this as a descriptive explanation. We could probably continue to multiply explanations indefinitely (e .g., a prenatal explanation might refer to what happened in the assembly plant, or a chemicalexplanation to differences in fuels used, but these five (the mechanistic, the evolutionary, the developmental, the intentional, and the descriptive) will be sufficient for our purposes.

It should be obvious that it is absurd to ask which of these explanations is the “right” one or the “complete” one. Each is appropriate in its own context. If we want to know how to manipulate the economy in such a way that automobile manufacturers produce more fuel-efficient cars, the evolutionary explanation would be

Stephen Wilcox and Stuart Katz

A Reply to Heil 315 appropriate. If we want to build an efficient car, a mechanistic explanation is necessary. If we want to know what we can do to treat our car so that it will not lose its efficiency, a developmental explanation would be required. On the other hand, the descriptive explanation would be perfectly useful if we were merely trying to buy an efficient car.

Now let us return to the question of how Gibson accounts for the “basis of our capacities to see what is there to be seen”. Gibson utilizes the equivalent of four of our explanations - the evolutionary, the developmental, the intentional, and the descriptive. The only one which Gibson might be accused of avoiding is the mechanistic, although a good case can even be made against this claim. For our purposes, however, the important issue is not how Gibson generally uses these various forms of explanation, but rather how the relativity of perception, i.e., the differences in the ability to see what there is to be seen, is treated within the Gibsonian framework.

First of all, it is not obvious that Gibson could be accused of “incompleteness” even if he were content with a descriptive account. If we could predict what an organism perceives from simple observable characteristics (as, of course, we can in many cases) there might be no need for any other account. Let us suppose, for example, that we find that mammals can see colors but fish cannot. We might try some other type of explanation, or we might simply elaborate our descriptive one. We might compare various types of mammals and fish or various identifiable types of animals within a species. At any time we could relate our findings to physiological differences, or to evolutionary histories, but such strategies are not inevitable or necessarily even useful. To reiterate a point, it depends upon the uses to which we intend our science to be put.

In practice, of course, Gibson goes beyond a simple descriptive account. In fact, evolutionary, developmental, and intentional modes of explanation tend to be intertwined. From the Gibsonian point of view all organisms perceive the world directly, although they only perceive part of it. Perceptual systems have evolved in relation to the organism’s particular needs. Gibson’s concept of ‘‘affordance” articulates this idea. The organism perceives the affordance structure of the environment, that is, what the environment affords for its own actions. And since different organisms have different modes of action, they perceive things differently.

This general principle is relevant at both the phylogenetic and the ontogenetic level. Just as a species develops its ways of perceiving in conjunction with its modes of action through its evolutionary history, an individual develops his or her ways of perceiving in conjunction with his

3 16 or her personal modes of action through his or her personal history. Thus the eagle, but not the sparrow, can see the rodent from 1,000 feet, and the chess master, but not the novice, can see his or her predicampt on the board. Why these differences? From one point of view, because of past histories; from another, because of present needs /purposes/intentions.

On the other hand, mechanistic explanations, although not ruled out, are often bypassed by Gibson. It is taken as a given that perceptual differences correlate with physiological differences, and with the overt actions which play a role in perceiving. But it is not logically necessary to take these into account any more than it is necessary to understand the internal combustion engine in order to drive a car. Again, it depends upon one’s purposes. The brain surgeon and the physiologist have to worry about nervous systems, since their manipulations are at this level, but perceptual psychologists have no such obligation.

In summary, Gibson has much to say about the “basis of the differences in our capacities to see what is there to be seen. ” Depending upon which aspects of the theory we focus upon, we can say that different organisms perceive differently simply because they are different organisms and there is no reason to believe otherwise, because they are the products of different evolutionary histories and thus inhabit different ecological niches, or because they have had different past histories and thus have different modes of action (or goals, intentions, etc.).

This brings us back to Heil’s claim that Gibson’s “theory is incomplete in the sense that it says nothing at all - or at any rate very little - about the basis of the differences in our capacities to see what is there to be seen.” We have seen that the theory has a great deal to say about this issue. What, then, is the basis of Heil’s claim? As we mentioned above, Gibson is mute concerning the internal processes involved in perception because he does not deem perception to be a collection of unconscious mental entities. To return to our automobile analogy, this would be equivalent to building a hypothetical model of the internal mechanism without being able to look at the plans or open the hood (cf. Ryle’s 1949, discussion of switch boxes). This type of explanation, however, is obviously what Heil seeks for the basis of perceptual differences.

In other words Heil accuses Gibson of failing to offer any explanation, because he (Heil) is only willing to accept as valid what we have termed the mechanistic explanation, and only one type of mechanistic explanation, the type which Gibson explicitly rejects.

History will decide whether or not Gibson is justified in characterizing as occult the approach to explanation favored by the psychological

Stephen Wilcox and Stuart Katz

A Reply to Heil 31 7 mainstream. In the meantime it seems only fair to admit that other forms of explanation are possible.

Stephen Wilcox and Stuart Katz Department o f Philosophy University o f Georgia Athens, Georgia 30601, USA

REFERENCES

DUHEM, P. The Aim and Structure o f Physical Theory. Princeton, N.J. : Princeton University Press, 1754.

EPSTEIN, W. What are the prospects for a higher-order stimulus theory of perception? Scandinavian Journal of Psychology, 1977, 18, 164-171.

HABER , R. Review of The Ecological Approach to Virual Perception, by J. J. Gibson. Science, 1780, 209, 779-800.

HAMLYN, D. The concept of information in Gibson’s theory of perception. Journal f o r the Theo?y o f SocialBehavior, 1777, 7, 5-16.

HEIL, J. What Gibson’s Missing. Journal of the T h e o v o f Social Behavior, 1780, 9, 265-267.

JOHANSSON, G. On theories of visual space perception. A letter to Gibson. Scandinavian Journal o f Psychology, 1970, 11, 67-77..

NEISSER, U. Gibson’s ecological optics: consequences of a different stimulus description. Journal for the Theory of Social Behavior, 1977,

REED, E. and JONES, R. Gibson’s theory of perception: a case of hasty epistemologizing? Philosophy of Science, 1978, 45 , 5 17-530.

RYLE, G. The Concept of Mind. N.Y.: Barnes and Noble, 1949.

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