Several years ago, the act ress Leslie Bibb perched next to Conan O’Brien’s desk and riffed about a baby so cute that it drove her crazy. She pantomimed her extreme reaction to the infant by gritting her teeth and clenching her fists.

A social psychologist named Oriana Aragón , who was then teaching at Yale, happened to be watching. In the days that followed, she found herself pondering a subject that doesn’t usually receive much attention from the scientific community: cuteness.

Dr. Aragón realized that feelings of tenderness can be so overwhelming that they spill over into a behavior that she calls “cute aggression.” An example, she told me, is “when you see a grandparent pinching a baby’s cheeks and saying, ‘I want to eat you up.’” In fact, sometimes baby-talk can sound downright serial-killer-ish if you take it out of context. You might find yourself telling a puppy that you want to squish it — even though, of course, you’re doing just the opposite and gently caressing it.

Dr. Aragón and her colleagues at Yale undertook what are probably the world’s first attempts to scientifically prove the existence of cute aggression. In an adorable experiment, she and her research partners handed volunteers bubble wrap, then showed them a parade of images. Dr. Aragón found that people popped more bubbles when looking at, say, a photo of a kitten than of an adult cat — suggesting that the cutest images do seem to prompt the urge to crush or squeeze.

Because the cute-overload feeling lends itself to study, it may help to reveal the parts of our minds devoted to nurturing that have heretofore been hidden.

Katherine Stavropoulos, a neuroscientist and clinical psychologist at the University of California at Riverside, has conducted a study on the neural circuitry that is active during cuteness-overload. She asked volunteers to wear caps outfitted with sensors that measure brain activity, and then showed them images of wee little animals. Her results suggested that “cute-aggression” involves the reward system in the brain. In other words, it feels good .

But why? “It’s just a completely open question,” Dr. Aragón, who now works at Clemson, told me. Even so, she points out, it’s reasonable to assume that our extreme reaction to cuteness is evolution’s way of making sure that parents do the relentless work of nurturing children. To perpetuate the species, parents must feel driven to hold their babies for hours — and that might explain why the urge to squeeze gets mixed into a cocktail of tender emotions.