Psychologists Attribute Yawning To The Need To Cool The Brain And Pay Attention

http://www.sciencedaily.com/releases/2007/06/070621161826.htm

The next time you "catch a yawn" from someone across the room, you're not copying their sleepiness, you're participating in an ancient, hardwired ritual that might have evolved to help groups stay alert as a means of detecting danger. That's the conclusion of University at Albany researchers Andrew C. Gallup and Gordon G. Gallup, Jr. in a study outlined in the May 2007 issue in Evolutionary Psychology (Volume 5.1., 2007).