New research shows that yawning is more contagious among family and friends than it is among strangers. Says study author Ivan Norscia, "the rate of contagion was greatest in response to kin, then friends, then acquaintances, and lastly strangers. Also the response gap (latency) โ€” or how long it takes to a person to respond to someone else's yawn โ€” is shorter in friends, kin and mates than in strangers." This was true across two different cultures and in a variety of situations. Researchers say contagious yawning can be a sign of empathy โ€” only people, chimps, and some types of baboons display this behavior.

Image via Ronald van der Beek/