Training for Tantrums

Are all kids born with the innate knowledge that in order to throw a proper tantrum one must hurl oneself on the ground? If so, Jacob might be in training for these future theatrics. Lately, when he's upset, he ever-so-gently lowers himself to the ground and puts one cheek on the floor. Then he cries a little bit. After that, he lifts himself up and crawls away, whatever upset him long forgotten. It looks suspiciously like a mild attempt at a tantrum. At the very least, he's assuming the flat-out-on-the-floor position.

Or maybe, just maybe - due to his inability to master sleeping through the night or taking naps that his mother deems an appropriate length of time - he's just tired.