Laughter as a window on the infant mind

What makes a baby laugh? The answer might reveal a lot about the making of our minds, says Tom Stafford.

What makes babies laugh? It sounds like one of the most fun questions a researcher could investigate, but there’s a serious scientific reason why Caspar Addyman wants to find out.

He’s not the first to ask this question. Darwin studied laughter in his infant son, and Freud formed a theory that our tendency to laugh originates in a sense of superiority. So we take pleasure at seeing another’s suffering – slapstick style pratfalls and accidents being good examples – because it isn’t us.

The great psychologist of human development, Jean Piaget, thought that babies’ laughter could be used to see into their minds. If you laugh, you must ‘get the joke’ to some degree – a good joke is balanced in between being completely unexpected and confusing and being predictable and boring. Studying when babies laugh might therefore be a great way of gaining insight into how they understand the world, he reasoned. But although he proposed this in the 1940s, this idea remains to be properly tested. Despite the fact that some very famous investigators have studied the topic, it has been neglected by modern psychology.

Addyman, of Birkbeck, University of London, is out to change that. He believes we can use laughter to get at exactly how infants understand the world. He’s completed the world’s largest and most comprehensive survey of what makes babies laugh, presenting his initial results at the International Conference on Infant Studies, Berlin, last year. Via his website he surveyed more than 1000 parents from around the world, asking them questions about when, where and why their babies laugh.The results are – like the research topic – heart-warming. A baby’s first smile comes at about six weeks, their first laugh at about three and a half months (although some took three times as long to laugh, so don’t worry if your baby hasn’t cracked its first cackle just yet). Peekaboo is a sure-fire favourite for making babies laugh (for a variety of reasons I’ve written about here), but tickling is the single most reported reason that babies laugh.

Importantly, from the very first chuckle, the survey responses show that babies are laughing with other people, and at what they do. The mere physical sensation of something being ticklish isn’t enough. Nor is it enough to see something disappear or appear suddenly. It’s only funny when an adult makes these things happen for the baby. This shows that way before babies walk, or talk, they – and their laughter – are social. If you tickle a baby they apparently laugh because you are tickling them, not just because they are being tickled.

What’s more, babies don’t tend to laugh at people falling over. They are far more likely to laugh when they fall over, rather than someone else, or when other people are happy, rather than when they are sad or unpleasantly surprised. From these results, Freud’s theory (which, in any case, was developed based on clinical interviews with adults, rather than any rigorous formal study of actual children) – looks dead wrong.

Although parents report that boy babies laugh slightly more than girl babies, both genders find mummy and daddy equally funny.

Addyman continues to collect data, and hopes that as the results become clearer he’ll be able to use his analysis to show how laughter tracks babies’ developing understanding of the world – how surprise gives way to anticipation, for example, as their ability to remember objects comes online.

Despite the scientific potential, baby laughter is, as a research topic, “strangely neglected”, according to Addyman. Part of the reason is the difficulty of making babies laugh reliably in the lab, although he plans to tackle this in the next phase of the project. But partly the topic has been neglected, he says, because it isn’t viewed as a subject for ‘proper’ science to look into. This is a prejudice Addyman hopes to overturn – for him, the study of laughter is certainly no joke.

This is my BBC Future column from Tuesday. The original is here. If you are a parent you can contribute to the science of how babies develop at Dr Addyman’s babylaughter.net (specialising in laughter) or at babylovesscience.com (which covers humour as well as other topics).