I've learned it's also called the "sensitive plant" because if touched the leaves fold up. I've seen them do this at night too.
Funny thing, one of these leaves (not sure how to exactly describe compound leaves) is missing a few of the stems on one side, see it in the photo above? Normally the foliage grows in pairs, on each side of the stem, but here there are four sets of leaves on one side, and a gap on the other. The stem bends a bit there, too. I wonder why the aberration in growth pattern?