What can six-month-olds do better than nine-month-olds? It turns out that six-month-olds are better than nine-month-olds at recognizing certain faces. In one study, scientists observed that six-month-olds are equally good at distinguishing between non-human faces, as they are at distinguishing between human faces.
Six-month-olds apparently have no trouble telling apart animal faces, but then they lose that ability by the time they turn nine months old. In contrast, as they get older, they just get better at distinguishing between human faces.
Know Where Your Bread's Buttered
It doesn't take babies long to learn that it's more important to pay attention to human faces than to animal faces. Scientists call this phenomenon cognitive narrowing. The more human faces babies look at, the better they get at noticing individual features.
At the same time, as they grow older, and their knowledge becomes more specialized, babies lose the ability to recognize animal faces, because they don't see nearly as many. And, as you might expect, when scientists tested this on monkeys, the opposite was true.
"Is Face Processing Species Specific During the First Year of Life?" (Science)
"Babies Can 'Tune In' Faces" (CNN)