DURHAM, N.C. Oxytocin, the "love hormone" that builds mother-baby bonds and may help us feel more connected toward one another, can also make surly monkeys treat each other a little more kindly.
Administering the hormone nasally through a kid-sized nebulizer, like a gas mask, a Duke University research team has shown that it can make rhesus macaques pay more attention to each other and make choices that give another monkey a squirt of fruit juice, even when they don't get one themselves.
Two macaques were seated next to each other and trained to select symbols from a screen that represented giving a rewarding squirt of juice to one's self, giving juice to the neighbor, or not handing out any juice at all. In repeated trials, they were faced with a choice between just two of these options at a time: reward to self vs. no reward; reward to self vs. reward to other; and reward to other vs. no reward.
"The inhaled oxytocin enhanced 'prosocial' choices by the monkeys, perhaps by making them pay more attention to the other individual," said neuroscientist Michael Platt, who headed the study and is director of the Duke Institute for Brain Sciences. "If that's true, it's really cool, because it suggests that oxytocin breaks down normal social barriers."
Earlier work by Platt's group had shown that macaques would rather give a reward to another monkey when the alternative is no reward for anyone, a concept they call "vicarious reinforcement." Their data in the latest study show an apparent improvement in vicarious reinforcement about a half-hour after exposure to oxytocin. Interestingly, for the first half-hour, the monkey was more likely to reward itself.
The researchers also tracked the monkeys' eye movements. Typically after making a prosocial choice, they will shift their gaze to the other monkey. Under the influence of oxytocin, the gaze lingered a bit more when they made other vs. neither choices.
|Contact: Karl Leif Bates|