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Insight into Brain Development
Evidence for "perceptual narrowing" in the ability to recognize faces, as also displayed when we lose abilities to differentiate between non-native sounds, such as those from foreign languagesand not because of memory deteriorationmay represent a more general change in early neural network development than previously thought, suggest the researchers.
"It's one way of looking at the bigger question of how brains develop into the adult like form: When babies are born, do they already have this little face and language area, do they have areas dedicated to specific functions?" explains Michelle de Haan, a co-author of the Science study. It is possible that a combination of natural changes in the brain between six to nine months of age and visual cues from the environment hone recognition capabilities, she says.
Brain systems for processing visual cues and speech may develop with a similar timing and influence each other and provides ample areas for further studies, the researchers write. "Although it is difficult to compare directly the tuning of speech perception with the tuning of face perception, there may be overlap between these systems."
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By adulthood, individual faces are "encoded" in terms of how they deviate from the brain's standardized face. The researchers knew from previous studies that adult humans are better at telling apart human faces than monkey faces, and monkeys, in turn, are better at telling apart other monkeys. Whether this was the case for infants with little experience with either species inspired the researchers to conduct several tests.
Two initial tests set the premise for the study. The researchers first observed brain waves to confirm young infants, but not adults, could discriminate monkey face identity across changes in facial orientation. In a second behavioral test turning the faces upside down only affected adults' brain waves for human faces, whereas in infants, it affected their brain waves similarly when identifying both humans and monkeys. These results provided some of the first clues that young infants might be better than adults at recognizing monkey faces.