Portraitists employing black-and-white film have long observed a psychological peculiarity: faces look unaccountably alien in negatives. Scientists at the Massachusetts Institute of Technology now know why and think the quirk might help explain how our brains process social cues.
Pawan Sinha, a brain scientist, showed subjects negatives of celebrities and statesmen and found the subjects could identify fewer than 60 percent of them. When he Photoshopped part of each negative and re-reversed the polarity of the eyes, producing what are called contrast chimeras, the same subjects now recognized three-quarters of the faces that baffled them before.
Much of what humans do as social beings requires reading and judging people’s faces. Eyes are the key to this, Sinha says, but not for the obvious, poetic reasons. It’s not that they are windows to the soul but that—unlike noses or jowls or hairlines—the shading of the eyes and eye sockets is utterly consistent across human beings. When the shading changes, our brains flounder.
To confirm this, Sinha observed his subjects’ brains in MRI machines while they studied both inanimate objects and negatives of faces. Pure negatives produced the same basic brain waves as tractors and other objects, but contrast chimeras lit up the specialized brain region, the fusiform face area, that normal photographs do.
The next step in this research is studying what preserves recognition in facial negatives without doctored eyes. (Lincoln’s beard and Nixon’s schnoz provide some clues.) More important, Sinha’s work could help psychologists understand aspects of autism. People with autism have trouble recognizing faces and picking up social cues. They also, research shows, focus solely on people’s mouths during interactions.
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