Frontiers

Looking for the Mind's Eye

April 2005
Light is bouncing off the page and entering your eyes, creating inverted shapes on your retinas. The shapes trigger chemical reactions in rod and cone cells, which send electrical impulses carried on optic nerves to the back of your brain. The impulses pass through the optic chiasma, with half from each eye entering each brain hemisphere. They collect in lateral geniculate nuclei – relay stations in each hemisphere - before shooting into your visual cortex.

And then...consciousness. You “see” the printed page.

If it seems like a step near the end of the process is missing, you’re right. Scientists have yet to grasp fully how neurons tripping inside the darkness of our brains can create the experience of vivid reds and brilliant blues, not to mention light, depth and motion.

“The very fact that you can open your eyes and see things is amazing,” says Gary Hatfield, the Adam Seybert Professor in Moral and Intellectual Philosophy. “But there’s a gap between the brain process and the experience itself. At present, we don’t have any real clue about how to bridge it.”

Hatfield is one of the most comprehensive thinkers regarding theories of vision and assorted philosophical streams of thought, such as philosophy of science and philosophy of psychology. He taught at Harvard and Johns Hopkins before arriving 18 years ago at Penn, where he co-founded the university’s Visual Studies Program. He is affiliated in some way with every program, center, study group and institute on campus that wrestles with the issues of human perception.

“In the philosophy department, he is the person to study this with,” says former student Morgan Wallhagen, Gr’04, who earned his doctoral degree last May and now teaches philosophy to Penn undergraduates. He says the opportunity to study with Hatfield was the deciding factor in his decision to come to Penn.

The disconnect between biological processes and conscious experience – known as the mind-body problem – is the missing link for cognitive scientists, perception researchers and philosophers such as Hatfield. “It’s a question for everyone who thinks in a scientific manner about the origin of living things,” he says from a couch in his Logan Hall office, surrounded by books stacked near to the ceiling. It is also a question that has occu-pied his thoughts from an early age.

Hatfield first took an interest in sight as a young boy growing up near Wichita, Kansas. His mother introduced him to the visual media through her painting and sculpting, while his father, a former biology teacher turned school principal, fostered a love of science in his preschool-aged son.

By the time he reached elementary school, Hatfield was hooked on the science of seeing. “My father brought home The Book of Knowledge, and I got completely absorbed in the process, including the relation between the brain and visual experience,” he recalls.

When the time came for his second-grade class to give presentations on one of the five senses, he learned firsthand the inherent problem of explaining visual perception. “One of the members of the class asked me a question about that. After I had finished the presentation, he asked, ‘But how does it really work? How does the brain really make us see?’ And there wasn’t anything else I could say.”So he began learning as much as possible about seeing and sense perception. Hatfield filled his high school electives with art classes and majored in history of art and psychology as an undergraduate. After receiving a doctoral degree from the University of Wisconsin, conferred jointly in philosophy, psychology and history of science, he was ready to investigate the mind-body problem.

What he encountered, however, was a fractured scholarly community that often shunned interdisciplinary collaboration. Philosophers approached the issue by exploring consciousness while brain scientists examined the phenomenon by tracking neural pathways. Communication between the two sides was virtually nonexistent.

For much of the 20th century, natural scientists followed the tenets of behaviorism, which seeks to explain humans without paying attention to mental events such as seeing the color red or psychological processes like getting angry. Because mental events were thought to be subjective, they were disregarded. “Most neuroscientists were uncomfortable with using a mentalist vocabulary to describe what the brain does,” Hatfield says. “That consciousness wasn’t talked about for a period of years was a matter of wishful thinking.” The mind-body problem was, essentially, swept under the rug.

A New Terminology
By the 1990s, some neuroscientists were sensing that a strictly behav-iorist approach was not sufficient to answer their questions about the human mind. They could not reconcile buzzing molecules inside the brain with human awareness. They began to consider philosoph-ical perspectives and gradually became interested in how theories of consciousness relate to their ideas about advanced brain processes.

“Consciousness is quite a difficult thing to analyze, and philosophers have been working on the description of consciousness for quite a long time,” Hatfield explains. “Neuroscientists realized that some of what philosophers had to say was useful.” For this cross-disciplinary hand-holding to prosper, however, it would need philosophers who understood the framework and language of neuroscience. Hatfield’s grasp of science and psychology facilitated this sharing of ideas.

“Professor Hatfield believes that philosophy should draw upon whatever body of knowledge that it can, whatever areas of inquiry might be relevant,” Wallhagen says. “He’s not dogmatic in the way that some philosophers can be. He thinks that work in the philosophy of the mind should be sensitive to the latest results in the relevant sciences.”

Today, Hatfield continues to foster the exchange of ideas between science and philosophy. He and Edward Pugh, an ophthalmology professor in the School of Medicine, recently finished a paper that seeks to create some common ground for scientists to discuss issues of consciousness. The paper focuses on qualia – mental states that are linked to sense and emotional perception. Running fingers over sandpaper, smelling a skunk, feeling a sharp pain and seeing bright purple
are all examples of qualia.

The paper is an attempt to convince philosophers and working scientists that qualia
have a place in nature and can be studied through the methods of natural science, contrary to the doctrine of behaviorism. Since scientists are often unsure about how to put consciousness into the scheme of nature, he and Pugh try to debunk the assumptions that have caused neuroscientists to fear qualitative data.

“Now, I don’t think that psychologists or neuroscientists have all the answers to my questions any more than I have all the answers that might arise from some of their concepts,” he says. “But I think we can both get a little further insight into the things we’re thinking about through this interchange.”

The ability to encourage dialogue is an aspect that Hatfield also brings to his teaching. “One of the things he does in the classroom, which is very difficult, is to engage the students in conversation so they are doing some of the work in class,” Wallhagen says. “Since he’s open to different approaches, he encourages them to follow their instincts, even if it’s a little unpopular.”

Whether people will ever develop a complete understanding of how they experience the world around them remains a topic of scholarly debate. For his part, Hatfield maintains that communication between philosophers and scientists will only further the creation of new knowledge about the human brain, an aspiration that his second-grade self would surely appreciate.

“I know a lot more now about how the brain works,” Hatfield says. “But the issue of how the brain really makes us see, in the sense of how does it produce conscious experience, remains a mystery. If you believe that life evolved from the primal ooze, then we must ask how consciousness came into that mix. It’s a fundamental question.”