Over the past 5 years numerous reports have confirmed and replicated the specific brain cooling and thermal window predictions derived from the thermoregulatory theory of yawning, and no study has found evidence contrary to these findings. Here we review the comparative research supporting this model of yawning among homeotherms, while highlighting a recent report showing how the expression of contagious yawning in humans is altered by seasonal climate variation. The fact that yawning is constrained to a thermal window of ambient temperature provides unique and compelling support in favor of this theory. Heretofore, no existing alternative hypothesis of yawning can explain these results, which have important implications for understanding the potential functional role of this behavior, both physiologically and socially, in humans and other animals. In discussion we stress the broader applications of this work in clinical settings, and counter the various criticisms of this theory.
Keywords: brain cooling, contagious yawning, sleep, thermoregulation, yawning
Citation: Gallup AC and Eldakar OT (2013) The thermoregulatory theory of yawning: what we know from over 5 years of research. Front. Neurosci. 6:188. doi: 10.3389/fnins.2012.00188
Received: 18 June 2012; Paper pending published: 25 September 2012;
Accepted: 06 December 2012; Published online: 02 January 2013.
Edited by:Melanie L. Shoup-Knox, State University of New York, USA
Copyright © 2013 Gallup and Eldakar. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
†Present address: Omar T. Eldakar, Department of Biology, Oberlin College, Oberlin, OH, USA.