Le bâillement, une relaxation innée !

Yawning is a phylogenetically old behavior that can be observed in most vertebrate species from foetal stages to death. Yawning appears as a powerful muscular stretch, recruiting specific control systems particularly the paraventricular nucleus of the hypothalamus, the locus coeruleus and the reticular activating system from which the vigor of this ancestral vestige, surviving throughout evolution with little variation, may increase alertness. By humans, yawning contributes to bodily consciousness as a behavior affiliating a sensory motor act and his perception from which pleasure is derived. Yawning can be seen as a proprioceptive performance awareness which inwardly provides a pre-reflective sense of one's body and an appraisal of well-being.