for National Geographic News
Human babies start out with the ability to recognize a wide range of faces, even among races or species different from their own, according to a new study.
The researchers focused on face processingthe ability to recognize and categorize faces, determine identity and gender, and read emotions. Their findings suggest that, in humans, this skill is a case of "use it or lose it."
In the study six-month-old infants were able to recognize the faces of individuals of a different speciesin this case, monkeys. Babies who received visual training retained the ability. But those with no training lost the skill by the time they were nine months old.
Led by Olivier Pascalis, a psychologist at England's University of Sheffield, the team reported their findings this week in the journal Proceedings of the National Academy of Sciences.
Training Babies for Face Recognition
To study early infant abilities, Pascalis and his team first tested a group of six-month old infants by showing them a series of pictures of the faces of Barbary macaques. Parents of some of the infants then regularly showed their children photographs of six Barbary macaque faces over a period of three months. The other babies were the control group and were not shown the monkey photos again.
The infants were retested at nine months of age. When babies in the control group were shown paired photos of mankey faces, the babies looked at each picture for the same amount of time. Babies who had been regularly shown monkey pictures by their parents spent more time looking at the pictures of new, unknown monkeys.
"A standard behavioral measure of familiarity with infants in visual processing is a measure of looking time," said Michael J. Wenger, a neuroscientist at Pennsylvania State University, who was not involved in teh study.
"One of the very regular things associated with visual recognition of any kind of object with infants is that they tend to prefer novelty. If you give them a choice between a novel and a familiar stimulus, they will typically always look more at the novel stimulus."
By looking at the novel monkeys longer, the visually trained babies demonstrated the ability to discriminate between the pictures of the monkeys they knew and pictures of monkeys they'd never seen before.
The study suggests that babies are born with a broad idea of what a face is. By the time they're nine months old, though, face processing is based on a much narrower model, one that is based on the faces they see most often.
This more specialized view in turn diminishes our early ability to make distinctions among other species, and possibly other races. For instance, if an infant is exposed to mainly Asian faces, he or she will grow to become less skilled at discerning among different, say, Caucasian faces.
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