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Monkey Behavior May Provide Clues to Autism

WASHINGTON, D.C.—A chance discovery of a macaque behavior could lead to new insights into autism. Among adult rhesus macaques, eye contact is a good way to get into a fight. But for newborns, time spent looking directly at the mother and, subsequently, imitating her facial gestures may be key to a well-adjusted adulthood. Individuals who don’t get this face-time tend to develop autistic-like behavior, rocking back and forth and failing to maintain good social connections, Stephen Suomi reported here yesterday at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW).

Monkey see. A macaque infant imitates its mother smacking her lips.
Credit: Laboratory of Comparative Ethology, DIR, NICHD, NIH

Suomi studies macaques at the National Institute of Child Health and Human Development, and has a large program in which he raises some newborns separated from their mothers to assess the effects of early development on adult behavior. In 2006, while filming macaque behavior, he and his colleagues discovered that mother macaques spend their newborn’s first week encouraging infants to look directly at them, a behavior thought to occur only in humans (see video). This contact and the imitative behavior that ensues—the infants will smack their lips in response to the mother doing the same, for example—helps bond the infant to the mother. Within a month, however, these face-to-face encounters cease; newborns stop imitating their mothers after just a week.

About half of the infants separated from their mothers, fed briefly by humans, and then raised among peers don’t respond to human efforts to get them to imitate. They quickly start lagging behind in their ability to reach out and grab objects, play half as much, and some later seem autistic.

In making the link between these abnormal behaviors and imitation, “we may have stumbled on a very early screening test for the risk of autism,” says Suomi. It could be that autistic children don’t imitate as young infants, though that has not been investigated. At the meeting Suomi described differences in the brain wave patterns between these individuals and those that do imitate when young, indicating that the face-to-face contact can lead to long-lasting physical effects in the brain.

“Neural development is retarded because of [a] lack of maternal-infant stimulation,” says Bruce McEwen, a neuroscientist at Rockefeller University in New York City. In the macaques, “the reciprocal interaction between mother and infant is critical for normal brain-behavior development and socialization.”

Suomi’s group plans to provide extra stimulation—and more face time either with humans or with 3D computer-animated macaques —for infant macaques raised without their mothers to see if their behavior later in life improves. The intervention may need to occur very early, as differences in imitative ability show up quite fast. “By day three, we already have a major rearing condition effect,” he points out.

See our complete coverage of the 2011 AAAS annual meeting in Washington, D.C.