What Happens to Your Hand After a Handshake?

Noam Sobel found a remarkable increase in the hand going to the nose after a handshake, and the motion is a sniff.

A study in his lab brought participants into the experiment room and told them the experiment would start soon. They did not know they were already being videoed. They sat for three minutes while the team later counted how often a hand reached the face, the nose, the forehead, or the chin. The baseline was not low. Three minutes later a new experimenter, meeting them for the first time, walked in and read a consistent script: equipment was still being set up in the other room, so they should keep waiting. In half of the cases the meeting included a handshake, and in half it did not. After a handshake, the hand went to the nose far more often. Nasal airflow, measured without participants knowing, showed the reach was perfectly timed with a sniff. People sniffed the hand that shook and also sniffed the other hand.

Sobel thinks the two sniffs compare self to other, and a lot of self-sampling might reflect the comparison.