Campus & Community

What you get is what you see

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Philosopher Siegel says consciousness determines perception

Susanna Siegel remembers staring up at the ceiling as a young girl and wondering whether the marks she saw on the white surface were tiny holes or tiny dots.

The experience got her thinking about how we perceive the world, how our senses and our minds take in sights, sounds, smells, tastes, and tactile feelings and form them into a coherent whole. It is a subject she is still thinking about.

In 2005, Siegel was promoted to a full professorship in Harvard’s Philosophy Department, where she has taught since 1999. Her colleagues are enthusiastic about Siegel’s promotion to tenure.

“Susanna brings much more to the department than just a fine research mind,” said philosophy professor Ned Hall. “It is not just that she is enthusiastic, open-minded, and curious about all areas of philosophy – and so, a wonderful source for the kinds of spontaneous philosophical conversations that are the lifeblood of any good philosophy department. It is also that her attitude toward training graduate students is just what our department needs at this stage in its history. She is deeply committed to graduate education here, and indeed the graduate students love her for it.”

Philosophy professor and department chair Richard Moran called Siegel “one of the most exciting young philosophers working today in the philosophy of mind and the philosophy of perception. We’re very happy she’s staying with us.”

One of the questions Siegel has grappled with is what role, if any, consciousness plays in perception. The question may seem self-evident to a nonspecialist. We are conscious (at least during our waking hours), and during these conscious periods, we simultaneously perceive the world and represent it in our minds. Obviously, there must be a connection.

But to a philosopher, the inference is anything but obvious. In fact, one school of thought – behaviorism – that was highly influential in the mid-20th century, assumed that the process of perceiving and representing the world has no connection with consciousness. This view, promulgated by the psychologist B.F. Skinner and the philosopher Willard Quine, asserted that there is nothing more to mental states than behavior.

A later view, based on the work of linguist Noam Chomsky and endorsed by much subsequent cognitive science, takes the computer to be the model of the mind, while the study of the mind is seen as a special case of studying computational processes. This idea challenges behaviorism, but arguably it still fails to involve consciousness in the perceptual process, because the computational model seems to leave no role for consciousness in the mind’s perception and representation of the world.

Siegel does not agree with either of these ideas. For her, consciousness is not a helpless ghost unable to prove its existence as the behaviorists would have it, or a sort of finish carpenter adding decorative elements to the underlying post-and-beam structure of mental processing. For Siegel, consciousness is essential to how we perceive and represent our surroundings.

“My view is that consciousness is very closely connected to representation,” she said. “Perceptual representation could not proceed just as it does without consciousness.”

Siegel believes that, in general, the process of acquiring expertise in a given area can influence perceptual consciousness. One example she gives to illustrate her belief comes from the realm of language. A person unfamiliar with Mandarin may view a page of Chinese characters and see only an array of incomprehensible squiggles. But after one learns to read the language, the same page will appear as recognizable words conveying a coherent meaning.

“The characters will actually look different to someone who has learned to interpret them,” Siegel said.

Or to use another example, a layperson viewing an X-ray may not perceive anything beyond a vague pattern of dark and light, but a trained radiologist will be able to look at the same X-ray and see evidence of a tumor. Siegel thinks this shows that the contents of perceptual consciousness is more than a mere assembly of colors and shapes.

Siegel has published several important articles on the nature of visual perceptual experience and is currently working on a book about this difficult and often perplexing subject. She breaks new ground by arguing not only that consciousness plays a part in perceptual experience, but that perceptual experiences themselves can represent causal facts, a view that philosophers since David Hume have tended to discount. Siegel’s work in this area may have profound implications for epistemology, the study of what we know and how we know it.

Siegel earned a B.A. from Swarthmore College in 1991, an M.A. from Yale University in 1993, and a Ph.D. from Cornell University in 2000. At Harvard she has taught courses in metaphysics and epistemology, the philosophy of mind, and the philosophy of language, as well as a Core course on moral reasoning about social protest. In addition, she is active in the interfaculty initiative, Mind, Brain, and Behavior, and serves as faculty adviser to the group Women in Philosophy, which promotes interest in philosophical issues among undergraduate women.