lpetrich

Great picture.

That new theory of hiccuping is that it's essentially a vestige of how gill breathing works. It may be preserved for the reason that embryonic gill bars and aortic arches are preserved -- it is difficult to get rid of these features because a lot of later features depend on them.

I wonder if something similar holds true for yawning -- is it a similar sort of vestigial feature?

Checking on PubMed, I find some experiments in making rats yawn; such experiments may eventually reveal the brain mechanism that directly controls yawning.

lpetrich

And here is my personal pet theory on why yawning is contagious.

Our minds work by creating mental models; these models often create fake perceptions, as when we "visualize" something.

So when we see some other individual yawn, we decide that that event is a yawn by comparing it to our own yawns. That's done with the help of a mental model that we unconsciously create of our yawns. But that mental model includes yawn triggering, and our brains may have an inadequate separation of modeled triggering and the real thing.

Thus, the contagion.

This theory will predict that yawning will be contagious among species with good mental-modeling ability, but there are very few such species other than our species -- great apes and perhaps also dolphins.

fando

You know how schools of fish swim in a synchronized fashion? I bet it's the same thing. There was a recent article somewhere that went over theories of synchronized behavior in animals and it covered yawning, howling, and many other "contagious" behavioral patterns. Maybe the link was already posted, I'm too tired to check... yaaawn... -_-

Nowhere357

I agree with this. It would have survival value, I think, if the whole pack/tribe tends to sleep at once.

Jackalope

Were is Fiach? He's the neurologist. I remember from my neurology courses that patients with certain types of brain damage could not voluntarily initiate certain behaviors like coughing but they could imitate that behavior if someone else did it where the patient could see. The classic one I remember from examinations is
doctor: Can you cough?
patient: uh...
doctor: [coughs lightly] cough?
patient: [coughs] yeah.

What I don't remember is whether or not yawning was one of those behaviors. I know that some types of damage cause excessive yawning. And asthma patients who don't wheeze often first notice an attack because they begin to yawn a whole lot.

lpetrich

As to imitating others' coughing, that may be a case of mental modeling in action; one's mental model of a cough may include one's triggering of it.

Just like what I'd proposed for yawning. That may explain why both scigirl and I have been provoked into yawning by seeing this thread. It makes us think about yawning, and if we are tired enough to want to yawn, then we yawn.

Corona688

*yawns* Curses, foiled again.

ps418

A similar thing can occur with smiling. I read somewhere (maybe it was Ramachadran's Phantoms in the Brain) about a stroke or other type of neurological patient with unilateral facial paralysis, that could not voluntarily smile. But his spontaneous smiles (as when his wife entered the room) were normal.

Patrick

Jesse

Kind people catch yawns

doghouse

Lesions in the supplementary motor area (medial part of the frontal lobe) can cause paralysis of the face with spontaneous emotional expression more affected than voluntary expressions. On the other hand, lesions of the primary motor cortex affect voluntary movements but not spontaneous (emotional) smiling.