A baby's first smile is an exciting moment. But what can it tell us about their understanding of the world?
From the 12-week scan right through the early years, monitoring the physical and mental progress of their pride and joy is a source of both excitement and concern.
Especially rewarding is the onset of smiles, squeals, and laughter - the kind of milestones that make all the disturbed nights worth it.
But is it all just wind?
Apparently not, as researchers now think that laughter and games like peek a boo could be telling us something more, and giving us a way to peer inside the workings of their minds.
"Laughter and smiles start incredibly early, just like tears," says Dr. Caspar Addyman, a baby laughter researcher at Birkbeck College in London.
"So this leads us to think that it's a form of communication," he told the BBC.
As a result of having experienced so little, small children are for the most part quite content to accept the absurd as completely plausible.
"Peek a boo is all the best things. It's mummy reappearing, but it's also about shared communication," says Dr. Addyman.
Joking requires an element of taking turns as well as other skills needed for advanced interaction, like imitation and eye-contact.
In fact, smiles and laughter could be important communication tools for infants before they develop language.The development of laughter
- 1-3 months - Babies smile for the first time
- 2-4 months - Social smiles develop, which actively engage the parents and are used to elicit a response
- 3-6 months - Babies begin to laugh
- 4-6 months - Babies laugh when tickled
- 6-8 months - Object permanence develops, which could explain why games like peek a boo suddenly become funny