On Looking: Eleven Walks With Expert Eyes by Alexandra Horowitz Page B

But they sit squarely at the center of our advanced social intelligence. There is a reason we can imagine others’ perspectives, have empathy, infer others’ goals, communicate—and it begins with a shared gaze.
    It could be a happy accident of pigmentation, this interest in each other’s eyes. The sclera of our eyes lost its dark coloration somewhere on the route between chimpanzee and human. With the whites of my eyes as backdrop to my bright blue irises, the direction of my gaze suddenly becomes plainly distinct. I cannot avoid being spotted looking at you by turning to the side and sneaking a peek out of the corners of my eyes. (Not only can you see me looking, I would look sneaky.)
    Even worse, as our ancestors came out of the trees and onto the plains, the entire shape of both our faces and our eyes changed. Our faces flattened: while the human face allows us to smush it fully against a windowpane or to receive a coating of pie froma pie tosser, the monkey’s face has a prominent snout, more like other mammals. The architecture of the human face is centered on the eyes, not the mouth or nose. Our cheekbones are conspicuously high—right below the eyes. The forehead and eyebrows complete the framing on the other side. Even the nose gets in the action, serving as an indicator of where our faces are pointing. Unlike most mammals, we have highly developed facial musculature, including around the eyes and even in the eye itself. What we lost in expressive potential when we lost tails is made up for by our ability to squint an ironic half smile—distinct from a full-bore joyous grin or a grimace. Along the way, too, the shape of our eye opening got squashed, revealing more of the whites.
    What pure disappointment these evolutionary developments might have been to their first bearers. Just when they thought that their attention was private, now everyone else could read it on their faces. It could be no worse if a Magic Marker traced a circle around your genitals when you felt attracted to someone, or your forehead scrolled the text rambling through your head in private thoughts.
    But our ancestors dealt with this change, and it was the harbinger of the development of the so-called social brain of present-day humans—one keen on others’ faces and eyes, and on the personhood behind those features. There is no one area in the brain that organizes our social understanding; instead, it is a network of regions in the cortex and subcortex, but especially parts of prefrontal cortex, right behind our forehead. There is something lovely about how eyes, windows to the mind, are contemplated in the space nearly right behind them. But they get there indirectly: the occipital cortex, processing raw data received through the eyes, is at the very back of the head.
    In that extra loop through the cortices of the brain, gaze gained meaning—lots of meaning. Gaze reveals that we are attending,and we react physically to seeing someone gazing at us. The sympathetic nervous system, responsible for revving up our bodies to run when we spy that lion, and for calming us when we are sitting down digesting dinner, treats gaze as something of interest. It reacts in the way it would if we saw a lion—just more moderately (unless it is a lion’s gaze). Adrenaline starts coursing through us, our heart pitter-pats, our breath subtly quickens, and we begin to sweat. How we feel about that rush of excitement depends on what we think the gaze means. And this depends on context: is it our lover gazing at us (I must really love him back) or is it that creepy guy across the subway car (I’ve got to get out of here)? Fear and sexual attraction are in the head; the body prepares the same way for both.
    In all events, the gaze is salient. We notice it, and we notice it from day one. Newborn babies can do very, very little when they first appear in this world, but they are already making one choice clearly. They prefer to look at a face looking toward