Thursday, 25 September 2014

Intellectualism Refuted (Part VII: Beyond Belief)

Gareth Evans (1982) argues that perception is belief-independent and in order to substantiate this claim he cites the well known example of the  Müller-Lyer optical illusion. He points out that despite any justified beliefs we may have about the actual lengths of the lines:  "[i]t will continue to appear to us as though, say, one line is longer than the other even when we are quite sure that it is not." Kelly (1998) endorses Evan's anti-intellectualist view that beliefs have no impact on our perceptions:

"Because perceptions are not subject to the canonical norms of rationality, then - because they are not, in other words, "rationally revisable" - they do not stand within the web of inferential relations that constitutes our beliefs, and ought not to be explained in terms of them."

For Kelly this web of inferential relations enables us to form beliefs, to make judgements and to infer conclusions. Despite the fact that there is no evidence to challenge this  conclusion, it remains a commonplace amongst philosophers to talk of "perceptual judgements" as if they are independent of "canonical norms of rationality." Evans is clear on this point. For him, judgement is connected with reasons and reasons are conceptual. If we are to avoid explaining perception by reference to "inferential relations" and "canonical norms of rationality" —of reasons— then something less extravagant than judgement is required.

We already have a candidate in Brook's theory of perception as a capacity to represent the things with which the  perceiver is engaged. In order to explore this conjecture it will be helpful to examine some frequently overlooked but nonetheless revealing anthropological research.

In one of the largest studies of its kind, Segal et al (1966) oversaw a global survey of cross cultural variations in susceptibility to optical illusions. The researchers found significant variance between differing communities and age groups. For example, some groups reported no difference between the lengths of the lines of the Müller-Lyer diagram. An earlier study by Hudson (1960), of culturally isolated South African children, encountered very similar findings. Both studies attributed the results to a lack of habitual exposure to pictures amongst the communities studied, and Hudson dubbed this: "pictorial illiteracy." In fact, even children well schooled in language and arithmetic skills (but lacking pictorial literacy) were not susceptible to what is commonly described as the "pictorial illusion of depth" and were therefore unsusceptible to the simulated spatial depth that many optical illusions exploit.

McCauley and Henrich (2006) write:

"For those who experience it, the illusion may persist, but susceptibility to the Müller-Lyer illusion is neither uniform nor universal. Moreover, a plausible argument can be made that through most of our species’ history most human beings were probably not susceptible to the illusion."

If this is true, and corroborating evidence can be provided from the art historical record as well as other sources (Deutscher 2010), then we have very good reason to suppose that our skills in the use of depictions are significantly implicated in the perplexities of such optical illusions. So, the conflicting responses we have when faced with the Müller-Lyer diagram are simply explained by the fact that we are disposed to represent the diagram in two different ways. We can treat the lines as a simulation of spatial depth or else we can treat them as two lines of equal length. No judgement need be imputed.

If the capacity to derive depth-cues from perspectival images is culturally acquired and is not an immediately available part of our genetically inherited perceptual repertoire then we have very good reason to suppose not only that perception is belief independent, as Evans claimed, but that perception is both non-conceptual and non-depictive. Language and depiction are skills that have developed through cultural evolution and both take time and practice to acquire. The capacity to imitate the behaviour of others on the other hand—to produce rudimentary versions of what Brook (1997) calls "Matching” representations—is an inherited skill upon which all of our more sophisticated communicative capacities supervene.

In Part VIII I will explore Kelly’s claim (pace Evans) that “Perceptual content is, sometimes at least, irreducibly articulated in terms of dispositions by the perceiver to act upon the object being perceived.” In doing so, I aim to explain how this gives strong support to the thesis that perception is fundamentally a communicative capacity: “a disposition to act” in representational terms “on [or with] the object being perceived.”


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