1.19.2009

The Face: What it Means
>

Men are red, women are green, the nose may be key to "reading" a face, and ordinary eyebrows may be what makes a face recognizable, rather than, say, provocatively bee-stung lips or baby blues. (Interestingly, in aspective Egyptian art, the convention is to show men as reddish in tone like the skin of a Spanish peanut, while women were shown in a yellowish tone, and the dead like Osiris, were green)

Those insights into how we "see" faces are part of the growing field of facial recognition, one of the hottest realms in psychology and neural science.

"It's very controversial: How do we see a face?" said Pawan Sinha, professor of vision and computational neuroscience at the Massachusetts Institute of Technology. Among the fiercely debated topics, he said, "is whether we learn to recognize faces or whether we come prewired with dedicated brainware for recognizing faces. The disagreement is deep - and rather sharp."

The focus on faces at universities and other research centers is far from purely academic. In the age of terrorism, police and intelligence agencies are clamoring for new technologies that can scan and accurately identify faces - winnow a "wanted" individual from the anonymous airport crowd, or a terrorist scoping out public buildings.

"Understanding how the brain works is the greatest mystery facing us in this century," said Garrison W. Cottrell, professor of computer science at the University of California in San Diego's Jacobs School of Engineering. "And facial recognition is among the greatest challenges to understanding the brain."

In pursuit of answers, psychologists and brain scientists have come up with some unexpected data.

Michael J. Tarr, codirector of Brown University's Center for Vision Research, recently published research in the journal Psychological Science that showed males have more reddish skin while women's skin has a greenish cast.

"The coloration is subtle, but actual - not just a trick of the mind or matter of perception. Men are redder, on average; women greener," Tarr said. "Color information is very robust."

The color difference, he theorized, may be because women need a certain skin pigmentation to better absorb ultraviolet light to synthesize vitamin B for lactation and bone development.

Meanwhile, research at the University of California in San Diego suggests people use the nose as a sort of main navigational point for charting a face.

Scientists found we focus first on the nose - looking just to the left of it, and then to the center - before deciding in a split-instant whether we recognize the person.

Other research suggests eyebrows may be as important as eyes when it comes to recognition. "Put on glasses with thick lenses or strange frames, and people will still recognize you," said MIT's Sinha, whose lab explores how the mind recognizes objects and scenes. "But shaving eyebrows is acutely disruptive to recognition."

Scientists aren't sure why, but one possibility is that eyebrows - like noses or mouths - are important because we recognize other features in relationship to them.
A very few people can be recognized by one salient feature - Jay Leno for his chin, for example. But most faces require fast mental computation," said Marlene Behrmann, professor of psychology at Pittsburgh's Carnegie Mellon University. "We are quickly measuring distances from nose to eyes, nose to mouth, eyebrows to cheek, before we recognize the face. It is these subtle relationships [of distance plus shape] that give most of us our individuality, not just our pretty nose or exquisite lips; those tend to be more similar to everyone else's than we'd care to admit."

No other object is as important for humans to recognize and interpret as faces, say scientists in the field.

"Unless you're an ornithologist, it's not important to know a robin from a sparrow; it's enough to recognize them as birds," Behrmann said. "But . . . to function in society, people have to recognize faces at a highly individualized level."

Nancy Kanwisher, a neuroscientist at MIT, is prominent among scientists whose research suggests a specific "sweet spot" in the brain - called the fusiform face area - has evolved to recognize faces. The ability is seen as coming as naturally as breathing or burping.

"Face perception may be a special domain of cognition, one with its own independent cognitive and neural machinery," she wrote recently.

But other scientists disagree, saying research points more to facial recognition as an acquired skill.

Clues to facial recognition can be found in conditions that hamper it.

Stroke victims and individuals suffering from autism have a tough time recognizing faces, as do people with a puzzling affliction called "prosopagnosia," or face blindness.

Researchers at Carnegie Mellon determined that individuals with prosopagnosia had disruptions in nerves connecting parts of the brain associated with recognizing faces.

"Most of us see the face as a whole, an assemblage. That's why you have no trouble recognizing your wife, but may not even notice her new hair style or lipstick," said Behrmann, a co-author of the study published last month in Nature Neuroscience. "People with the condition, however, can only see the parts, not the larger pattern."

Labels: , , , , , ,




Links to this post:

Create a Link



<< Home

This page is powered by Blogger. Isn't yours?