There are several references to this on the internet, but this is the reference that I first came across, so this is what I’m linking to. From Ingrid Fetell Lee:

Did you know that the Navajo (Diné) people have a specific tradition around celebrating a baby’s first laugh? Around three months, they watch the baby closely for that first real giggle. The person who has the good fortune of eliciting that first laugh is then responsible for throwing a party, with the baby technically playing the role of host. Of course, a baby can’t host a party, so the relative or friend who coaxed out that first laugh hands out rock salt, candy, and gifts on the baby’s behalf.

I love this tradition, if for nothing else then for the cuteness factor alone. There are more reasons to celebrate this event, though: laughter is a baby’s first form of communication with its surroundings and with other humans. From this great Ted.com article referencing psychology researcher Caspar Addyman:

The need to communicate with laughter may have deep roots in our development as a species, speculates Addyman. Evolutionary biology suggests it’s a way for humans to share with other humans — and thus, to belong. While he is still teasing out why children needed to signal their enjoyment of the cartoon to whoever was there, he thinks it has to do with the idea, raised by Oxford University anthropologist and primatologist Robin Dunbar, that laughter could be a replacement for the earlier primate behavior of grooming. “Grooming was a one-on-one, unfakeable investment of time in somebody else,” explains Addyman, and it created trust among group members as well as a sense of community.

We have several different baby-event celebrations; this should be one of them!