There is an universal tendency among mankind to conceive all beings like themselves, and to transfer to every object, those qualities, with which they are familiarly acquainted, and of which they are intimately conscious. We find human faces in the moon, armies in the clouds; and by a natural propensity, if not corrected by experience and reflection, ascribe malice or good- will to every thing, that hurts or pleases us. —David Hume
Our brains are made to find faces. In fact, they’re so good at picking out human-like mugs we sometimes see them in a jumble of rocks, a bilious cloud of volcanic ash, or some craters on Moon.
Neuroscientists from the Massachusetts Institute of Technology wanted to investigate how the brain decides exactly what is and is not a face. Earlier studies have shown that the fusiform gyrus, located on the brain’s underside, responds to face-like shapes—but how does it sort flesh from rock?
The researchers could conclude that the left side of the brain ranks images on a scale of how face-like they are. The right side makes the categorical distinction between whether or not it’s a human face.
The left side of the fusiform gyrus actually flared up before the right side supporting the hypothesis that the left side does its job first and then passes information on to the right side.
Sources: Ars Technica - Skepdic.com.