This is a story about a fickle little hormone that plays a large role in our lives. The name of the hormone is oxytocin, and until recently it was mostly dismissed by scientists. They knew it played a role in inducing labor and facilitating breast-feeding, but otherwise didn't give it much attention. But over the past 10 years, oxytocin has come up in the world, and several researchers have begun making big claims about it. Now dubbed the trust hormone," oxytocin, researchers say, affects everything [in] our day-to-day life. To understand the role that oxytocin plays in your own life, consider the experience of a small 9-year-old girl named Isabelle. Isabelle has Williams syndrome, a rare genetic disorder with a number of symptoms. The children are often physically small and often have developmental delays. But also, kids and adults with Williams love people and are pathologically trusting: They literally have no social fear. Researchers theorize that this is probably because of a problem with the area in their brain that regulates the manufacture and release of oxytocin. Paul Zak, a researcher at Claremont Graduate University, ... says that in a normal brain, oxytocin is generated only after some concrete event or action: "When someone does something nice for you - holds a door - your brain releases this chemical, and it down-regulates the appropriate fear we have of interacting with strangers." Suddenly, you are filled with a sense that the person before you is not a threat. And then just as quickly, according to Zak, it disappears. "This is a quick on/off system." Unless, of course, the system gets disregulated, which is what Zak and other scientists say happens with Williams syndrome.