laughter = trust?

I've been spending a lot of time with Elliot recently.  For pretty much the past 3 weeks I've been the weekday caregiver.  Which is both awesome and exhausting.  I got sick last week and I don't think the timing was a coincidence.

One interesting effect is that Elliot laughs more around me.  He would always smile, but laughs were harder to elicit until recently.

It seems pretty clear that laughter, for an infant, is an expression of trust.  He is more likely to laugh with people he trusts.

Which led me to ponder:  does this remain true?  Am I more likely to laugh at the joke of someone I trust and feel comfortable with, than with a stranger?  (I'm talking about true laughter, not the fake nervous laughter that we often trot out for someone's terrible joke at a party.)

It seems to me that in adulthood history becomes more important than trust.  That is, if someone has been funny in the past, I'm more likely to laugh at something they say.

Put in infant terms, this is a kind of pattern recognition:  that face is the funny face, it's the one I laugh at.

Come to think of it, maybe that's all Elliot is doing, pattern recognition.  I think we're building trust, but really we're building a history of him laughing at me.