Cuteness cutoff: Why kids older than 4 1/2 are not as cute to us

Moms, do you miss the days when your kids were squishy, adorable little babies? Don't feel guilty — according to a pair of recent studies, your brain may be hardwired to feel that way.

The first of the studies suggests that kids stop being unbearably cute around age four-and-a-half, while the second indicates our nurturing instincts kick in at the sight of those baby features.

For the first study, psychologists in China and at the University of Toronto asked 60 men and women to evaluate the likeability and attractiveness of a large sample of children's faces from infants all the way up to six-year-olds. The subjects rated younger children's' faces more highly than those of older children, who in turn were thought more adorable than adults.

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That's not too surprising. What is more interesting, though, is that the cut-off between ultra-adorable and just plain cute was around age four and a half, when kids' facial structure start to show some significant changes. Infants have a special set of features that we have evolved to find adorable, including a large head, a round face, large eyes and a small nose and mouth.

Here's where the second study comes in. Researchers in Italy, Japan and Germany found that even when childless adults looked at the pictures of human babies, parts of the brain associated with picking up or talking to an infant become active.

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Those results build on past research suggesting an evolutionary link between babies' cuteness and adults' desires to care for them and ensure their survival.

"These adults have no children of their own. Yet images of a baby's face triggered what we think might be a deeply embedded response to reach out and care for that child," senior author Marc H. Bornstein of the Eunice Kennedy ShriverNational Institute of Child Health and Human Development, says in a statement.

In other words, humans have universally evolved to find babies' faces adorable, even when the babies aren't our own. And that undeniably cute factor starts to wane around age four or five, when kids are no longer completely dependent on their parents for survival.

So don't worry about missing that chubby little baby face — it's science.

Check out this CBC news video about an Australian couple who paid a fortune for their baby to be born early in a Vancouver hospital.