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20 décembre 2001
1989; :193-194
Yawning and Simulation Science
Robert R Provine
Department of Psychology University of Maryland Baltimore
Autres articles de R. Provine et R. Baenninger


Yawning is a remarkable behavior that is overlooked only because it is so commonplace. Consider the phenomenon of contagiousness. You yawn or are tempted to yawn when you observe someone else yawning. You are not tempted to yawn by a desire to imitate the yawner. The observed yawn triggers an inborn visual recognition process in our brain that is programmed to detect yawns. When the yawn detector is activated, it triggers the stereotyped act of yawning.

Observed yawns produce a chain reaction of yawning that synchronizes the behavior and probably the physiological state of the group. The analysis of such contagious yawning provides insights into a very ancient and previously ignored class of neurologically mediated social behavior. Contagious yawning also provides a useful, although unlikely, tool to investigate the more general problems of neural and computer pattern recognition.

Because visually observed yawns trigger yawns, contgious yawning can be used to assay the activation of the neurological yawn detector. In other words, contagious yawning can teach us about the underlying logic of visual pattern detection. Using this approach, our laboratory has been able to specify the features of the animate yawning face necessary to evoke contagious yawning.

In our first approach to this problem, a videotape of a yawning face was edited so that various facial features such as the mouth could be presehted in isolation, or a feature such as the mouth could be deleted from an otherwise intact face. The rather surprising result was that the video image of the gaping mouth, one of the most obvious features of a yawning face, stimulated few yawns. In fact, a yawning mouth presented out of the context of the yawning face was an ambiguous stimulus. The isolated mouth could be that of someone yelling or singing. This result complemented the finding that a videotaped yawning face lacking a mouth was as effective a yawn-evoking stimulus as an intact yawning face.

A series of such analyses indicated that the neurological "yawn- detector" was activated by the overall configuration of the yawning face, not by a single feature such as the mouth. This result complicated the analysis. The invariance in the visual stimulus that is the unique signature of the yawn must involve a specific, time-ordered change of a constellation of features. Computerized line cartoon simulations of yawns offer a complementary, more reductionistic tactic for identifying the stimulus configuration that activates the brain's yawn detector. In contrast to the relative wealth of visual complexity and redundancy of the videotaped images, the cartoon representation of yawns relies upon the most skeletal element of visual form, the line. Line cartoons of any type, including smiling faces and stick men, are recognizable representations of reality because they are attuned to the brain's neurological shorthand for visual features. There is a lot of psychology and neurology in cartoons.

The use of computer-generated visual displays allows the experimenter to specify the yawning stimulus in both space and time. (High-quality speedups and slowdowns of animation sequences are difficult to accomplish with videotape technology.) The first step in producing realistic line cartoon animations of yawning involves knowing what to animate and then producing a high-quality visual display of the data. A low-quafity display that evokes no yawns of observers would produce an indecisive result; we would not know if some essential element of the yawn were omitted, a potentially interesting result, or if the display was simply toc, crude to be effective.

A microanalysis of the normal yawning face produced the graphic data base necessary for the simulations. This rather labor- intensive exercise (two student summers in duration) involved the measurement of thousands of individual frames f rom video-taped records of 48 yawns produced by 12 subjects. Special attention was given to the shape and area of the mouth and eyes, and their relation to the overall configuration-of the yawning face.

Preliminary line animations from these data have been produced with an antiquated Apple Il computer. We have just started examining the relative yawn-evoking potency of yiwns differing in duration, mouth shape, change in mouth area over time, and degree and timing of eye squint. However, further analyses must await the acquisition of a fast, powerful graphics computer.

I regret leaving you with an account of an experimental journey that has just begun, but the logic of the approach may be informative, even for those with no interest in yawning. Bigger issues are at stake. At the very least, the present analysis should tell us something about preprogrammed visual recognition mechanisms in our brains. The identification of a mechanism for yawning establishes a precedent for what may be a general class of neural visual feature detectors. Yawning research may also provide insights into the difficult applied problems of how to produce, store, sort, transmit, and recognize biologically relevant visual images of people and objects. The present tale about yawning teaches us that there is an inherent relation between the biological, psychological, and synthetic domains.