Now we come to the IgNobel prize in physiology, though this study isn't really what you'd associate with physiology. It's more what you associate with behavior. A shared behavior. Yawning.
(Sci has to note that I yawned about 5 or 6 times during the writing of this piece. Can't seem to help it. What IS it with writing about yawning and yawning? That's it, from now on I'm writing down every time I yawn during this piece.)
Yawns are notoriously contagious in the human species. From the way we talk about it, you'd think that every time one person yawns, the whole world ends up yawning with them. And it IS true that about 50% of the time (ok, 40-60% to be exact) when you yawn and are observed by someone else, they will yawn as well.
But the contagiousness of the yawn is now just limited to humans. *yawn* (Yeesh!). Dogs can share yawns with us and with each other, and many other primates also share yawns (though the meaning of yawning in primates is a very different thing). Yawning is a fixed action pattern, a series of movements that, once it starts, can't be stopped (*yawn*). In humans, yawning has been thought to do various things, including cooling the brain (link), increasing arousal when you're sleepy so you don't sleep, and (*yawn*) possibly as a form of communication to synchronize group behavior, by communicating drowsiness, social stress, or maybe just being bored.
So is yawning a form of unconscious empathy? Do we do it to spread social behavior? This would mean that, in order to have a contagious yawn, the animals involved would have to be capable of empathy, of fellow feeling. We know that dogs and primates and humans probably are (well, humans most of the time), but that means we can't really test for whether it's empathy or not. We need a species that is social, but probably can't feel fellow feeling for its compatriots.
It's is TIME! BRING IN THE TORTOISES!!!! (tortoises? tortoise? tortoisii?)
WIlkinson et al. "No evidence of contagious yawning in the red-footed tortoise Geochlone carbonaria" Current Zoology, 2011.
I feel bad for this species actually. With a name like carbonaria, I can't help thinking of pasta the whole time.
To test whether yawning requires empathy, and thus get at the real purpose which yawning might serve (cooling the brain anyone?), the authors took a bunch of red-footed tortoises. This special is highly social, and totally cool with living together. They trained one of the tortii to yawn when exposed to a red dot.
Then they had test tortoisae watch the trained tortoise in action, and checked them for yawns. They also checked for yawns when no other tortoise was present, and when the trained tortoise had no red dot, and so wasn't yawning.
Side note: one of the things I love about this study is that all of the subjects had names. I'm a personal fan of the one they named Wilhelmina.
Anyway, what they got was a big fat negative. The test tortoise showed no notice of the other animals huge yawns. The same thing happened in all the other trials, with the tested tortii showing no yawning reactions to conditioned yawns, recorded yawns, nothing. That tortoise doesn't give a s*** if you yawn.
So what does this big pile of negative data mean? It means that contagious yawning is NOT just the result of a fixed action pattern triggered when you see someone else yawn. If that were the case, the tortoisees would have yawned right along with their compatriots. It means that contagious social yawning requires something more, a social sense or sense of empathy resulting from complex social interactions. Or at least, interactions that are more complex than those in tortoises. Of course, it COULD Mean something else, that tortoises are just a really bad choice for contagious yawning. But the social explanation seems a little more supported.