Monkey See, Monkey Pay

In discovering that monkeys will "pay" in fruit juice to see images of other monkeys, neurobiologists Michael Platt and Robert Deaner have discovered a highly useful animal model for studying autism.

In their experiments, reported on the March issue of Current Biology, the researchers gave male rhesus macaque monkeys juice rewards for glancing at either a neutral target on a computer screen or images of other monkeys. By systematically varying the juice rewards and the images--including a gray square, higher- or lower-ranking monkeys, and female hindquarters--the researchers could precisely measure how much reward a monkey would "pay" to see which images.

They found that the monkeys would forego a significant amount of reward to see an image of a higher-ranking monkey or one of female hindquarters. The study's aim, says Platt, was to bring into a controlled laboratory setting the kinds of social judgments that monkeys were observed to make in the wild. Such an achievement could offer an extraordinary scientific opportunity to study the "neural wiring" that underlies social cognition. And, if parallels do exist between monkey and human social machinery, laboratory studies of monkeys could help explain how that machinery goes awry in autism.

"One of the main problems in people with autism is that they don't find it very motivating to look at other individuals," he says. "And even when they do, they can't seem to assess information about that individual's importance, intentions, or expressions.

"So, what we now have with these monkeys is an excellent model for how social motivation for looking is processed in normal individuals. And, it's a model that we can use to explore the neurophysiological mechanisms of those motivations in a way we can't do in humans. We can use drugs that affect specific neural processes to explore whether we can mimic some of the deficits found in autism in these animals."