Interview - Dr Caspar Addyman

How did you come up with the idea for the research?

It started about four years ago with my sister’s second baby. My brother is a stand-up comedian. And I thought, why wouldn’t you be interested in making a baby laugh? Almost nobody in developmental psychology was looking at this behaviour.

What did you find out from your worldwide survey?

One of the key messages we found was that we laugh and smile very early. The average age of a baby’s first smile was 1.5 months, and the first laugh was 3.5 months.

We asked parents, ‘What is the one thing guaranteed to make your baby laugh?’ Tickling was by far the most common answer.

We also asked what babies found the funniest toy or game. And across all countries the answer was peekaboo. Peekaboo works because you give the baby your full attention; you cannot play peekaboo when you’re checking your phone, or without eye contact. It is popular between six months and two years.

An interesting development happens at around a year when babies discover they can make you laugh. It’s telling that the funniest game for babies is basically a conversation without words. Laughter is about communication and connection. We’re also starting to look at whether laughter helps babies to learn. We did an experiment and found that yawns aren’t contagious in babies, but laughter captures attention.

How does laughter help babies’ language and social development?

Laughter exists to encourage social play. When a baby is laughing, this interaction is a conversation. Laughter is part of the reward given by babies – laughter and crying.

In evolutionary terms, when did humans start laughing?

We don’t really know. But laughter is definitely older than language. We first started speaking between 200,000 and 600,000 years ago. But our relatives the chimpanzees have laughing behaviours, and we diverged from them six million years ago. Laughter is probably even older than that.

Tell us about your book

The Laughing Baby is about the science of infant learning and why happiness matters right from the start. I thought parents would appreciate a book that explains infant development through the lens of laughter. The book is crowdfunded by publisher Unbound. You can pre-order it at https://unbound.com/books/the-laughing-baby

• Dr Addyman was speaking at the National Literacy Trust’s annual Talk To Your Baby conference.