This is scientific American 60 second science. I'm Christopher Intagiyata.

A baby's laugh is unmistakable.

But aside from its squealing high-pitched quality, there's another factor that sets a

baby's laugh apart from hours. Babies laugh on the exhale and the inhale,

whereas adult humans tend to last predominantly on the exhale, so the classic kind of ha, ha, ha.

Desis Sauter, a psychologist who studies emotions at the University of Amsterdam.

Sauter and her colleagues collected 44 samples of babies laughing,

from the ages of three months,

to ten months,

all the way up to 18 months.

They played the samples for about 100 untrained volunteers

and asked them to deconstruct the laughs.

Where the baby's laughing on the inhale, the exhale, or both.

And there we find a nice relationship between the age of the baby and the amount of the laughter that is happening

on the inhale. The younger the baby, the more laughs on the inhale. Because remember,

our laughs gravitate towards the exhale as we age, and Sodder thinks one reason for that

could be that we gain more vocal control as we learn to talk, because speaking also happens

primarily on the exhale.

She presented the preliminary findings

at a meeting of the Acoustical Society of America

in Victoria, Canada.

And now her team is in the process of checking

...