Oxytocin is a hormone found to be crucial in the formation of loving bonds between mothers and babies, and it's thought to just generally makes people feel more sympathetic and connected to each other. That's definitely true of rhesus monkeys.
Duke University researchers hooked up some of these monkeys to a child-sized nebulizer - a gas mask, basically - that sprayed the hormone oxtyocin up their noses. The monkeys were then presented with a bit of fruit juice and trained to choose who received the juice. The options included taking the juice for themselves, giving it to monkey seated next to them, or nobody getting it at all. The monkeys were only ever presented with two of these options at a time.
For the first thirty minutes of these experiment, when the extra oxytocin still hadn't really been absorbed by the monkeys' bodies, the monkeys tended to look out for themselves, either choosing to take the fruit juice or, if that option wasn't presented, to give it to no one. But, as the oxytocin began to take effect, the monkeys became much more inclined to give the squirt of fruit juice to their neighbor. Team leader Michael Platt explains:
"The inhaled oxytocin enhanced 'prosocial' choices by the monkeys, perhaps by making them pay more attention to the other individual. If that's true, it's really cool, because it suggests that oxytocin breaks down normal social barriers."
The researchers studied the monkeys' eye movements. When monkeys make a prosocial choice - one that benefits others more than themselves, basically - they will tend to look over at the other monkey. Under the influence of oxytocin, the monkeys gazed for much longer at their neighbor. Whether this is the rhesus monkey equivalent of getting lost in somebody's eyes is a question best left to future research.
But that, amazingly, is not the question Platt is most concerned with. Instead, he is optimistic that oxytocin can also be used in humans to promote more social behavior, and could form a part of treatment for mental conditions like autism and schizophrenia. Indeed, almost exactly the same setup used with the monkeys could be replicated in human treatments, as Platt explains:
"We were able to make the inhalation very tolerable by using the pediatric nebulizer. This may be much better for treating young children with autism or related disorders than the typical nasal spray, which can be uncomfortable. It may deliver the hormone more effectively, too."
Working with monkeys in research like this is crucial because we need some way to evaluate the long-term effects of oxytocin before trying it out on humans. And more traditional test subjects, like rats, are just too different in their brains to be of much use.