Thursday, 29 June 2017

The Rationality of Perception

In this post, Susanna Siegel, Professor of Philosophy at Harvard University, introduces her book, The Rationality of Perception.

On a traditional conception of the human mind, reasoning can be rational or irrational, but perception cannot. Perception is simply a source of new information, and cannot be assessed for rationality. I argue that this conception is wrong. Drawing on examples involving racism, emotion, self-defense law, and scientific theories, The Rationality of Perception makes the case that perception itself can be rational or irrational.

The Rationality of Perception argues that reasoning and perception can be deeply intertwined. When unjustified beliefs, fears, desires, or prejudices influence what we perceive, we face a philosophical problem: is it reasonable to strengthen what one believes, fears, or suspects, on the basis of an experience that was generated, unbeknownst to the perceiver, by those very same beliefs, fears, or suspicions? I argue that it is not reasonable-even though it may seem that way to the perceiver. In these cases, a perceptual experience may itself be irrational, because it is brought about by irrational influences.

Here’s a simple example. Jill fears (without good reason) that Jack is angry with her. As a result of her fear, Jack’s face looks angry to her when she sees it. If you saw Jack, you’d see his neutral expression for what it is. There’s no need for Jill to jump to conclusions from what she sees. Her fear’s influence on perceptual experience makes it simpler for her: she can just believe her eyes.

Let’s suppose that Jill has no idea that her fear has influenced her perceptual experience. To her, she’s simply seeing Jack, and following common sense in believing her eyes - since as far as she can tell, she has no reason not to believe her eyes.

Is it reasonable for Jill to believe her eyes, when her visual experience is a projection from an unreasonable fear or presumption? It might seem that the answer is Yes. What else is Jill supposed to believe, given that she has no idea her fear has been projected onto her experience? In countless other situations, it’s reasonable to believe what you see. If you want to know whether there’s mustard in the fridge, for instance, then if you see some mustard (and have a visual experience of a sort that typically goes with seeing mustard), it’s clearly reasonable to believe that the fridge contains mustard.

On the other hand, there’s something fishy about Jill’s strengthening her fear on the basis of her perception, given the role of the fear in generating the key aspects of her visual experience – the aspects that make the fear seem reasonable. If Jill’s fear starts out unreasonable, how could it become reasonable, just by shaping the crucial contents of a visual experience?

Here we have one of the classic forms of a philosophical problem. There’s a seemingly straightforward Yes-or-No question, where both answers seem plausible.

This problem has many potential instances. Here are some others:

Preformationism: When spermist preformationists (who favored the hypothesis that sperm cells contained embryos) look at sperm cells under a microscope, their experiences have embryo-content, due to their favoring preformationism. They go on to believe that the embryos contain sperm cells, and to strengthen their confidence that preformationism is true.

Vivek: Vivek is a vain performer. He is irrationally overconfident that his audiences as well as casual observers look at him with approval. When he sees their faces, he has visual experiences in which those faces look approving, even when their expressions are in fact neutral.

Gun: After seeing a face of a man who is black as a conscious prime, a participant whose task (in an experiment) is to decide whether a subsequent object he is shown is a tool or a gun has a visual experience of a gun when seeing a pair of pliers. He goes on to believe that the object is a gun, and the outlook which associates between black men and guns is strengthened.

Threat illusion: To a man whose mind manifests culturally entrenched racial attitudes toward black men, a boy playing in a playground who is black looks to the man like a much older teenager dangerously wielding a gun. The illusion (age, threat) arises because of Man’s racial attitude that black men and boys are dangerous. The perception of threat occurs in the man’s visual experience.

These cases all give rise to the same problem as Jill’s situation when she sees Jack.

The problem illustrated by these cases has many potential solutions. Some solutions say that the correct answer is Yes, some say it is No, some say it is both Yes and No, depending on the dimension of reasonableness at issue. For any potential solution, a full defense would identify the features that would make it reasonable or unreasonable for the subjects in the examples to believe their eyes.

Normally, perceptual experiences have a power to help justify beliefs formed on the basis of those experiences. The philosophical question about these cases is whether the power of experiences to justify believing one’s eyes is reduced by the influence of psychological precursors, or whether that power is sustained despite such influence.

The solution I defend in The Rationality of Perception is that the correct answer is No, due to the relationship between the psychological precursor and the perceptual experience. That relationship, I argue, can be inference: perceptual experiences can be inferred from psychological precursors. When the relations is inference, and the perceptual experience is inferred from the psychological precursors, then the experience can lose epistemic power.

The main point of the book is to explain how experiences could arise from inference. The idea that perception results from inference has a long history in Psychology. But the kind of inference at issue in Psychology is usually not the kind at issue in The Rationality of Perception. What’s at issue in The Rationality of Perception is whether perceptual experiences can result from the kind of inferences that redounds well or badly on one’s rational standing.

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