Like Humans, Monkeys Can be Snobs Too

Feb. 28, 2006 -- -- No question about it, in some ways we humans are very much like monkeys.

Scientists at the Duke University Medical Center have found in past research that, like some humans, monkeys will "pay" for the attention of a monkey of higher social rank, and even to see the female hindquarters of another monkey. And now they've added even more evidence of the similarity between monkey and human behavior.

Monkeys, it turns out, can be snobs.

For several years now, neurobiologists at Duke have been studying how monkeys perform in a social situation, or more specifically how the brain is wired to deal with social cognition. It's all part of ongoing research into autism, which affects more than 1 million Americans and is the fastest-growing developmental disorder.

Persons suffering from autism have much difficulty in dealing with social situations, including paying attention to what's going on. So several years ago Michael Platt and Robert Deaner began studying rhesus macaque monkeys to see if they could figure out how these cleaver animals deal with their social challenges.

In early research they found that monkeys, like humans, pay considerable attention to what others in the room are looking at. We humans see that all the time at parties. One person turns to see who just entered the room, and in a split-second the rest of us take a gander too.

The research, using sophisticated timing devices, showed that the action was almost instantaneous among monkeys as well as humans. If one monkey saw an image of another monkey looking to the right, it looked instantly to the right.

Building on that work, the researchers decided to see if monkeys would be willing to forego some of their juice for various privileges, including seeing an image of a monkey with a higher social rank, or looking at a bit of monkey porn.

Monkeys were willing to "pay" for both those treats, but they weren't willing to pay a drop of juice to see a picture of a monkey with lesser status. In fact, they wanted to be paid to look at riff-raff. Give them juice, and they'll look, but otherwise forget it.

That set the scientists to wondering, "is it possible that what seems to be an involuntary reaction, like following the gaze of another, can be influenced by social standing?"

In the latest experiment, the monkeys were shown photographs of members of their colony with varying social status. Each image showed a monkey gazing either to the right or the left. The researchers measured the time it took for each monkey to look in the same direction as the monkey in the photo.

And here they found a significant difference. Monkeys of high social status cared less about where the monkey in the photo was looking. It took them twice as long to respond as those with lower social status, who responded in one-10th of a second.

The latest research, published in the journal Current Biology, (lead author Stephen Shepherd), indicates that part of the response was automatic, a built-in demand that monkey does what monkey sees. But the difference in status shows that the overall response consists of both a reflexive and a voluntary component. Social status dictated part of the response.

The research also suggests that social status may have a biological component. The high status monkeys have an elevated level of the male sex hormone testosterone, and the scientists think that may suppress the level of "social vigilance," thus allowing them to take longer to respond.

Monkeys on a lower rung of the social ladder aren't quite as charged up with testosterone, and are twice as likely to have their attention diverted by the simple gaze of another monkey. Easy distraction, by the way, is a key symptom of autism.

So while the research may seem funny, it's quite serious. The discovery of a biological component to any disorder may open new avenues for treatment.

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