Human vision can provide our brains with new visual information 60 times each second. Our eyes can detect colors that most mammals have never known. Their frontal placement on our heads allows us to perceive depth. At close range, we can somehow make out details that should be too small for our lenses to focus on. On the other side of the equation, eyes are also one of our favorite things to look at, preferably on a human face. Or even non-human faces. Or maybe just inanimate objects that are sort of arranged like a face, if we’re in a pinch. Looking at faces seems to be hard-wired into our brains, and we know that even newborns will look longer at faces than other stimuli. One catch to really understanding this impulse has been the difficulty of getting a good look at younger brains to see how it develops over time.
The most precise way to see brain activity today is through functional magnetic resonance imaging (fMRI). Subjects can sit inside the large machine and interact or view different stimuli, and researchers can get a picture of their brain in action, as long as they don’t wiggle too much. Like shaking a camera while you take a photo, fMRI needs its subjects to hold still, which is why working with squirmy kids and babies gets difficult. To overcome some of this, researchers have designed special seats and even allowed babies’ mothers to crawl in the machine with their infants to keep them calm while they looked at pictures of trees, landscapes, and of course, faces.
Ready to go, with room for improvement
The picture painted by two different studies is that our brains start with a lot of built-in visual processing capabilities, but that some of those capabilities grow and become more sophisticated as we age. Infant brains showed visual processing activity that was basically fully realized. Their brains didn’t need to slowly be taught how to parse differences between trees and faces, as those circuits were ready to go at least as early as four months of age. Some specialization was also apparent, with some brain structures showing preferences for human faces similar to what’s been observed in adults.
The second study, which involved a wider variety of ages, found that just because those preferences are built-in at birth, they’re not static. Focusing on a structure called the fusiform face area (FFA), researchers found that this bit of brain tissue actually grows more densely connected over time. Adults seemed to have more connective dentrites between neurons than children, as well as more protective myelin around those connections. This is in comparison to other visual processing areas, which did not show the same increase in complexity in older and older subjects.
Advancing into adulthood
Aside from throwing anatomical support behind humanity’s love of looking at each other, there are practical and theoretical implications in these findings. For people with more densely-packed fusiform face areas, remembering faces is actually easier than for people who aren’t as connected, like my three-year-old who still identifies adults by the legs he sees at eye-level. It also indicates that while brains don’t need to develop these structures from scratch as we grow up, they are growing for much more of our lives than previously thought. While the prefrontal cortex is now thought to be “grown” by age 25 or so, it seems that structures that facilitate what we really care about keep developing our whole lives. Selfies are big for a reason, right?
Source: Peekaboo! Baby Brains Process Faces Just Like Adult Brains Do by Christopher Wanjek, Live Science