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mise à jour du
30 octobre 2005
American Scientist
Robert R Provine
Department of Psychology University of Maryland Baltimore USA
Autres articles de R. Provine et R. Baenninger

Extract : Unconscious Control
You cannot yawn on command. This observation is the best evidence of yawning's unconscious control. Yawns occur either spontaneously or as a contagious response to an observed yawn. Intense self-awareness, as when you are being observed or even suspect that you may be observed, inhibits yawning. I already had experimental evidence of this inhibition when I began studying yawning contagion, providing the rationale for the use of self-report in experiments. As my yawning studies attracted attention (the popular media have a voracious appetite for stories on this topic), I had the experience of seeing the inhibition play out.
A television news-magazine crew turned up one day to tape a segment. Against my advice, the show's producer set out to recreate my experiment in which one-half of a large lecture class read an article about yawning while the other half read a control passage about hiccuping. Normally the effect of the yawning article is robust, and it has been used as a demonstration of contagion in classes at other universities. As I predicted, the demonstration did not survive up-close-and-personal scrutiny by a national network television crew. With the cameras rolling as the students read, only a tiny fraction of the usual amount of yawning was observed.
The video crew performed an unintentional but informative variant of my original research demonstrating the powerful effect of social inhibition on yawning. Even highly motivated and prolific yawners who volunteered to be on national television stopped yawning when placed before the camera. It is notable that the social inhibition of yawning occurred unconsciously and was not the voluntary effort of the yawner to suppress a rude or inappropriate act. A socially significant act can be either produced or inhibited by unconscious processes. Scrutiny also inhibits hiccuping, an act that is also unconscious but is not contagious.
When piano students in my wife's home studio start hiccuping, she signals me to bring my tape recorder into the studio to record their sounds. In all nine cases where we have used this technique, my appearancewith recorder and microphone has been followed almost immediately by an end to the hiccuping. I've thus discovered an effective treatment for the hiccups while finding further evidence for the social inhibition of an unconsciously controlled act. When the ancient and the new, the unconscious and the conscious compete for the brain's channel of expression, the more modern, conscious mechanism dominates, suppressing its older, unconscious rival.
Too little is known for this article to end with a dazzling intellectual flourish and a Grand Unified Theory of Yawning. It is customary at this point, though, to suggest a need for further study, and indeed I see much potentia in using yawning to develop and test theories of mind and to better understand certain neuro- and psychopathologies. Here I have attempted to describe the yawn, when we do it and its promise for study, without speculating about function.
Yawning appeared very early in vertebrate history, with contagiousness evolving much later. Yawning has many consequences, including opening of the eustachian tube, tearing, inflating the lungs, stretching and signaling drowsiness, but these may be incidental to its primal function which may something as unanticipated as sculpting the articulation of the gaping jaw during embryonic development. Selecting a single function from the many options may be an unrealistic goal. However, reviewing the disparate facts, I'm impressed that yawning is associated with the change of behavioral state wakefulness to sleep, sleep to wakefulness, alertness to boredom, threshold of attack, sexual arousal, switching from one kind of activity to another.
Yawning is a vigorous, widespread act that may stir up our physiology and facilitate these transitions, with the motor act becoming the stimulus for the more recently evolved contagious response. Consider the Bakairi people of central Brazil as observed by their first European visitor, 19th-century ethnologist Karl von den Steinen. Irenäus Eibl-Eibesfeldt recalls in his 1975 book Ethology that Steinen reported: "If they seemed to have had enough of all the talk, they began to yawn unabashedly and without placing their hands before their mouths. That the pleasant reflex was contagious could not be denied. One after the other got up and left until I remained with my dujour.
Among all members of our species, the chain reaction of contagious yawning synchronizes the behavioral as well as the physiological state our tribe. Yawning is a reminder that ancient and unconscious behavior lurks beneath the veneer of culture, rationality and language, continuing to influence our lives.
Figure 2(Tom Dunne). The physiological requirements for a yawn can be determined with a self-experiment. A normal yawn (top left) involves gaping jaws, a deep breath and a shorter exhalation. If you pinch your nose when you begin to yawn, you will find that you yawn quite normally; the nostrils are not necessary for the deep inhalation. A clenched-teeth yawn, by contrast, is impossible, revealing the yawn to be a complex motor program requiring gaping jaws. Finally, if you try a "nose yawn"Ñinhaling only through the noseÑyou will find that inhalation through the mouth is an essential component of the yawn.