Before babies have the words to tell us what they're thinking, they can laugh.

Infant giggles are undeniably adorable.

They're one of babyhood's most joyful milestones.

And it turns out these joyful moments have a serious side too.

For scientists, infant laughter can provide a window into understanding how babies' minds develop during their first year of life.

So when do babies start to laugh and why? What do they find funny? Why do some babies laugh

at almost anything while others have a more serious temperament? When do babies start trying to make

other people laugh? And what can this progression tell us about baby's cognitive development and how

they experience the world? Welcome to Speaking of Psychology, the flagship podcast of the

American Psychological Association that examines the links between psychological science and everyday life.

I'm Kim Mills. My guest today is Dr. Gina Moreau, a professor of psychology at Vermont State University,

where she directs the infant laughter lab.

She studies how babies discover what is funny, how they perceive, interpret, and respond to the unexpected in social contexts,

revealing the earliest foundations of humor

and social understanding. Her research has been funded by the National Science Foundation and the

National Institutes of Health and covered by media outlets, including CNN.com, NBC Nightly News, and PBS's

Nova Science Now. She recently wrote an op-ed for the New York Times called

The Evolutionary Brilliance of the Baby Giggle. Dr. Murrow, thank you for joining me today.

Thank you so much for having me. Let's start with the basics. How early do babies start to smile

and laugh and does smiling come first or do both actions emerge around the

same time? Well, smiling comes first. Babies actually smile in utero. So it's an involuntary smile.

And most parents will observe this smile when their babies are brand new to the world. But these smiles are involuntary.

...