Contagiosité des comportements humains : la réplication du bâillement peut-elle nous éclairer ?

Abstract

Yawning is a stereotyped behavior, observed in cold-blooded and warm-blooded vertebrates, from reptiles with rudimentary “archaic” brains to human primates, in water, air, and land environments. Yawning appears to be an ancestral vestige maintained throughout evolution with little variation, bearing witness to its early phylogenetic origins. Three different types of yawning can be distinguished. “Universal yawning”, which is seen in all vertebrates, is associated with daytime circadian rhythms, i.e. sleep/arousal and hunger/satiety. “Emotional yawning”, which is only seen in mammals (and perhaps birds), has a calming effect after stress. Ethologists call this type of behavior a displacement activity. Finally, “contagious yawning”, which is observed only in great apes, in humans, in elephants, in dogs under certain conditions and perhaps in social parrots (budgerigar), rats and pigs, is the ability to respond to yawning in others. Experimental research indicates that contagious yawning relies on the capacity known as mental state attribution on one hand, and the capacity to build knowledge of mental states in oneself, on the other. These two conditions involve a “theory of mind” (TOM). This ability to infer mental states and emotions in others represents an evolved psychological capacity most highly developed in humans and, up to a point, in non-human primates and elephants. In addition, humans can also empathize with others, that is, share their feelings and emotions in the absence of any direct emotional stimulation to themselves. Innate emotional and motivational processes are found to exert unconscious and automatic influences on social judgments and behavior. Contagious yawning, the onset of a yawn triggered by seeing, hearing, reading, or thinking about another person yawning, occurs as a consequence of the ability to infer or empathize with what others want, know, or intend to do, requiring the neurological substrate responsible for self-awareness and empathic modeling, by which a corresponding response is produced in oneself. Functional imaging suggests that activation of the underlying network integrating these processes is also responsible for decoding cognitive empathy. As a neocortical activity (inferior-frontal cortex, superior temporal sulcus, ventral premotor cortex, right parietal cortex, posterior cingulate, anterior insula, and amygdala), contagious yawning is a sign of involuntary empathy. Thus, we see that, through evolution, a behavior can be recycled for different purposes according to the increasing complexity of the central nervous system, correlated with the richness of social interactions. Researches on this involuntary behavioral replication are an unrecognized avenue to study mimetic social processes.