Funky monkeys:

Michael Platt never planned to study autism; he was just a boy who loved monkeys. “Every time I did a school project, it was about evolution,” he says. It was an obsession that wasn’t necessarily encouraged in the working-class Catholic neighborhood just outside of Cleveland where he grew up. Platt was the captain of his high school football team and in 1985 was recruited to play for Yale University. When he arrived, however, he quickly realized he didn’t want to be a jock. He took a course in primate evolution and soon got hooked, sorting through monkey bones in the drawers of the university’s Peabody Museum of Natural History.

After his third year at Yale, Platt spent three weeks in a summer field course on Totogochillo Island in Mexico’s Lake Catemaco, which hosted an introduced colony of stumptail macaques. The experience gave him an appreciation of the richness of the social lives of monkeys. It was also where met his future wife, Elizabeth Brannon, whose work now focuses on the behavior of human infants. While in graduate school, Platt tried to study wild wedge-capped capuchin monkeys in the seasonally flooded forests of Venezuela. It rained so much there that the trails disappeared under three feet of water teeming with anacondas, and the forest was so leafy he could hardly see the treetops where the monkeys were. One day in July 1991, he shot a pregnant monkey with a tranquilizer dart, aiming to catch her on a sheet. But he lost track of her in the canopy, and she crashed to the ground. She survived but the fetus did not.

Devastated, Platt fled from field work. He joined Paul Glimcher’s lab at New York University as a postdoctoral fellow, learning to record the activity of neurons in monkey brains in order to better understand how monkeys make decisions about what to look at. Platt was probing a murky region of the brain that sits between the visual and motor areas of the parietal lobe. He found that neurons in this region, called the lateral intraparietal area, fire more frequently when the monkey expects either a reward or a high probability of receiving the reward. His 1999 paper on this finding launched a new paradigm called neuroeconomics, which marries economic theory to the study of brain activity.

Platt took this nuts-and-bolts approach with him when he joined the faculty of Duke University in Durham, North Carolina. His goal then was to unlock the neurobiology underlying the social behavior of a dozen macaques he kept in the lab. Whom we look at — and who watches us looking — is a fundamental part of human relationships. During a conversation, when one person looks to the left, the other person reflexively follows the gaze. The reflex develops in early infancy, setting the stage for our complex social lives. Platt knew that primates, including macaques and chimpanzees, also seem to develop this behavior, but children with autism often do not. (Unlike mice, dogs and some birds also pay attention to the human gaze.)

In an early study, Platt and a postdoc in his lab, Robert Deaner, tracked how long it took people and monkeys to move their eyes to a yellow target that randomly appeared on the left or right side of a screen. Before the target flashed, an image of a monkey face would appear, gazing to either the left or the right. People and monkeys both shift their gaze more quickly in the correct direction when the image of the monkey face is also looking in that direction. Platt also recorded involuntary eye movements called microsaccades that are thought to indicate a shift in attention and expectations. The data from people and monkeys were almost identical, suggesting to Platt that both species process gaze the same way.

Platt grew convinced that monkeys, with their stripped-down cultures and customs, hold the key to cracking open fundamental questions about how our social brains develop — and, potentially, what happens when this typical development goes awry. In an experiment published in 2005 that he called “Monkeys Pay Per View,” he found that male monkeys were willing to forgo a juice reward to look at a photo of a high-ranking male or a female’s rear end (the equivalent of monkey smut). But he had to bribe them with an extra squirt of juice to get them to look at the lowliest members of their group. He later monitored which neurons were firing and found that the lateral intraparietal area is also involved in keeping tabs on the social hierarchy.

Soon, parents of children with autism began showing up at his talks and asking him the kind of question he was never trained to answer as a scientist: “What does this mean for us?” The pressure made Platt think about how to make his experiments more relevant to people, he says. “It was the first time I began thinking more seriously about the clinical implications of my work.” One of the people who witnessed this transformation was Geraldine Dawson, former chief science officer for the research and advocacy group Autism Speaks, which began to fund his research. “Michael’s interest in autism went from being strictly scientific to one that moved him emotionally,” she says.

When Platt was up for tenure at Duke, his department chair encouraged him to switch his focus to mice in order to take advantage of new genetic tools. Platt ran a study of decision-making in mice, but his heart wasn’t in it, and he never published the results. “I had no feeling for that organism at all,” he says. He was convinced that monkeys could provide answers mice never could. But he couldn’t keep more than two monkeys in a single cage at his lab — severely limiting his ability to study how monkeys socialize.

His best bet was to return to the field.