We often make fun (and rightly so) at the pareidolia phenomenon when it happens to Christians spotting Jesus's face on an old sock or the Virgin Mary's face on a piece of toast. The fact remains that our brains are really good at spotting faces and this is why we see them in inanimate objects. Naturally, most normal people can immediately tell that it is not a real human face staring back at us. But how does our brain decide what is a real human face and what only looks like a human face? We know that the fusiform gyrus (part of the temporal lobe, towards the bottom of the brain) is involved in face and body recognition (and also in the processing of color information and word recognition). But how does it sort out real from not real? Neuroscientists did an experiment using photos of real faces and photos of faces ion rocks, etc., that machines mistakenly label as human faces, and measured brain activity of volunteers looking at the pictures by fMRI. They found different activity patterns in the right and left side of the brain. The left side would flare with activity whether the face was real or just an eerie rock formation, but the right side of the fusiform gyrus had a very different activation pattern whether the face was real or whether it was something that only resembled a face. The researchers conclude that the left side does its job face in ranking something as a face-like image, transmits the information to the right side, and the right side makes the distinction between a real human face and something that only looks like it, however eerily similar it may be to a face. This clear distinction of function is one of the first known examples of the left and right side having different roles in high-order visual processing tasks.
By Mark Brown, Wired UK
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 the Moon.
But another amazing thing about our brain is that we’re never actually fooled into thinking it’s a real person looking back at us. We might do a second take, but most normal brains can tell the difference between a man and the 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?
Pawan Sinha, professor of brain and cognitive sciences at MIT, and students created a procession of images ranging from those that look nothing like faces to genuine faces. For the ones in the middle — structures, formations, smudges and shapes that give us a pareidolic reaction that causes us to see a face — they used photographs that machine vision systems had falsely tagged as faces.
By doing a series of one-to-one comparisons, the human observers rated how face-like each of the images were. And while the subjects sorted out the photographs, functional magnetic resonance imaging (fMRI) was used to scan their brains and look for activity.
Read the rest here.