"According to Jay Belsky, a leading proponent of this view and a psychology professor and child care expert at the University of London, the reactivity of these kids' nervous systems makes them quickly overwhelmed by childhood adversity, but also able to benefit from a nurturing environment more than other children do. In other words, orchid children are more strongly affected by all experience, both positive and negative. Scientists have known for a while that high-reactive temperaments come with risk factors. These kids are especially vulnerable to challenges like marital tension, a parent's death, or abuse. They're more likely than their peers to react to these events with depression, anxiety, and shyness. Indeed, about a quarter of Kagan's high-reactive kids suffer from some degree of the condition known as "social anxiety disorder," a chronic and disabling form of shyness."