Photo by Rick Geary

Animal yawns may promote alertness.

Dear Matthew Alice: Why don’t I feel the urge to yawn when I watch my cats yawning? I can’t get them to yawn either. Is yawning only contagious to the human race? — Carol Wilson, San Diego

When Fluffy and Snookums chase imaginary mice, claw the sofa, or hat at flies, do you get the restless urge to do the same? Strongly flock-oriented animals are sensitive to other members’ behavior; when one bird decides to take a bath, odds are the rest will try to crowd into the tub with him. But cross-species imitative behavior may be stretching the “monkey-see, monkey-do” idea a bit too far. Truth is, your cats probably can’t even get other cats to yawn, so I think it’s asking too much for them to trigger a yawn in you. Based on admittedly sketchy data, yawnologists (both of them) believe the contagion phenomenon is a strictly human susceptibility. No one has observed chain-reaction yawning in a herd of moose or a boxful of puppies, though a behavior resembling the human yawn can be seen in practically every type of animal, including reptiles and fish.

The one persistent problem of yawn research is the so-far uncrackable nut of why we yawn at all. Or why hippos or lizards yawn. Or exactly what a yawn is, for that matter. Aside from the fact that you and your cats are of different species, your yawns may not be easily communicable because they serve different purposes.

One researcher observing animal behavior found that individuals as diverse as lions, mandrills, and Siamese fighting fish yawned in anticipation of some major event (feeding time at-the zoo in the case of the lion and mandrill, a fight in the case of the fish). It may promote alertness, opines the prof. There’s a parallel in human behavior, runners preparing for a race, students taking exams, actors about to go onstage, and others in a state of nervous anticipation often yawn quite frequently, and the behavior seems unrelated to fatigue or boredom.

What little research that has been done on the human yawn seems mostly to confirm what each of us already knows. Subjects whose mouths were taped shut reported that their subsequent yawns were “unsatisfying,” that some important element was missing. This suggests that yawning is linked closely to stretching — that it’s a way to limber up the facial muscles. The conclusion is supported by the fact that the labor-inducing drug oxytocin stimulates both stretching and yawning. Research findings with subjects in high-oxygen and low-oxygen environments make researchers skeptical about the longstanding belief that yawning helps oxygenate people’s blood when they’re fatigued.

Some epileptics and people with encephalitis or brain tumors yawn a lot; schizophrenics rarely yawn. Why? Who knows?

The one thing that yawn research has confirmed in a dozen ways is that humans are extremely sensitive to yawn-provoking cues. Subjects viewing videotapes of yawners will yawn at twice the “normal" rate; even pictures of just the eyes, mouth, or other facial feature of a yawner act as a stimulus. By contrast, videotapes of people smiling provoke few smiles from test subjects. Blind people yawn when they hear audiotapes of yawners. And as you may have already found out, reading about yawning does it too. The only thing all this researching and yawning can’t tell us, once and for all, is why we do it.