title: Why do we yawn? The importance of evidence for specific yawn-induced effects.
abstract: Gallup (this issue) believes that our recent review on the function of yawning (Guggisberg et al., 2010) is unbalanced and that it ignores evidence for his thermoregulation hypothesis. Here we address these criticisms and show them to be untenable. While we never claimed that the social hypothesis of yawning has "definite experimental support", we emphasize the importance of experimental evidence for specific effects of yawns when considering why we yawn. The only specific effect of yawning that could be demonstrated so far is its contagiousness in humans, some non-human primates, and possibly dogs, whereas all studies investigating physiological consequences of yawns were unable to observe specific yawn-induced effects in the individual of any species. The argument that from an evolutionary perspective, yawns must have a "primitive" physiological function arises from imprecise reasoning.
authors.affiliation: University of Geneva, Department of Clinical Neurosciences, Division of Neurorehabilitation, Avenue de Beau-Séjour 26, 1211 Geneva 14, Switzerland. aguggis@gmail.com
authors.forename: Adrian G
authors.initials: AG
authors.lastname: Guggisberg
authors.forename: Johannes
authors.initials: J
authors.lastname: Mathis
authors.forename: Armin
authors.initials: A
authors.lastname: Schnider
authors.forename: Christian W
authors.initials: CW
authors.lastname: Hess
mesh_terms: D000818:Animals; D004285:Dogs; D006801:Humans; D007100:Imitative Behavior / Q000502:physiology*; D012919:Social Behavior; D015000:Yawning / Q000502:physiology*