Let's go back to Matrim laughing.
Now, I'm not what anyone would describe as "baby crazy," however, I am fascinated with human development. I am also, because of my 'night job' inherently interested in the idea of a sense of humor, and what makes things funny. The anatomy of a laugh.
To me, a baby laughing in response to a non physical stimulus is the most interesting thing a baby can do because it's a sign of the development of thought process as well as a sign of a developing sense of humor.
To break it down developmentally, Matrim is 15 months old which puts him in the Sensory Motor cognitive stage of development. He is not just a little adult. His brain works differently than mine or yours. He achieves all of his learning through his senses and his developing physical relationship with the world.
By four to eight months infants engage in repetitive behavior to produce interesting effects, such as batting at a mobile to make it move. Or, in the case of Matrim's YouTube video, dropping a toy to produce a noise/make his uncle pick up the toy again.
By the time an infant is fifteen months these repetitive behaviors increase and take on even more intention, as the effects can be predicted by the baby.
When you want to start talking about the beginning of the Development of a Sense of Humor you're beginning to talk about Social Development.
Babies smile in recognition of their mother or father's face or voice when they are only two months old in some cases. They laugh by the age of four months, usually in response to tickling or facial recognition. It's not until months and months later that laughter is elicited by engaging in games like "Peek a Boo." The reason is that only by then has the baby gained the cognitive concept of "object permanence." When Mom's face disappears Baby knows she's behind her hands, but there is some very tense time waiting for her to return. When she does return, with a noise and an abrupt motion Baby laughs, the same way we jump and laugh at the sudden loud noises in scary movies.
But by the time an infant is Matrim's age he is actually finding humor in noises or events. He might laugh if Mom or Dad pretends to eat his food. Or if they make funny faces. This in and of itself is fascinating to me. I have spent many a day in Baystate Children's Hospital trying to make an infant laugh. And most babies past 8 months have already developed enough sense of taste to know what's funny and what's just not. Think about that for a second.
But THEN, even more amazing, the infant learns how to make other people laugh. The same way physical cause and effect was once established, social cause and effect begins to set in when he begins to process which actions or events are positively reinforced by the laughter of those around him.
Matrim, although he is unable to stand on one leg or talk in complete sentence, can make a joke. He is intentionally repeating an action that he knows will be funny, and he thinks it's funny too.
Someday he will move on to more sophisticated humor: first, intentionally garbled words in otherwise familiar songs, moving on quickly to non sequitors, and graduating eventually to puns and knock knock jokes by the time he's nine*. The rule of three comes later. Scatological jokes though, as far as I can tell, are forever.
If the kid is smart, no matter what he'll keep playing to his audience as well as he does now.
And then we'll go on tour.
* Uncles automatically revert back to this stage once they become Uncles.