Why do people love looking at Tai Shan, the National Zoo's overexposed celebrity panda cub? What's with that so-cute-I-could-melt thing, anyway?

Stephan Hamann, a psychology professor at Emory University in Atlanta, has conducted a number of studies on brain responses to pleasant stimuli, including pictures of cute baby seals and puppies. He uses functional magnetic resonance imaging, which is sensitive enough to measure tiny changes in brain activity. His studies found that "cute" pictures cause increased activity in the middle area of the orbital frontal cortex, located behind the bridge of the nose, and in the amygdala, the emotion-control center of the brain responsible for fear and arousal.

According to Hamann, increased activity in the middle orbital cortex is usually associated with pleasure and positive emotion. Some evidence suggests the brain activity there is greater when the stimulus is "neotenous," which is to say it has juvenile characteristics — a button nose, big eyes, a large wobbly head, chubby extremities or pudgy cheeks.

So, why are even crotchety people hard-wired to prefer cuteness? Konrad Lorenz, an Austrian zoologist who shared a Nobel Prize in 1973, was the first of many researchers to conclude that cuteness, or "baby schema," is an evolutionary adaptation that triggers nurturing responses from adults.

Surprisingly, Hamann says, "Men and women showed nearly identical responses to cute stimuli, even if for social reasons they rate it differently."

In other words, even though men may not as easily admit to thinking something is cute, their brains tell another story.