Are You Yawning Because Your Brain's Hot?

Everyone knows yawning is the pinkeye of social cues: powerfully contagious and not that attractive. Yet scientists aren't sure what the point of it is. Is yawning a form of communication that evolved to send some message to our companions? Or is the basis of yawning physiological, and its social contagiousness unrelated? A new paper suggests that yawning--even when triggered by seeing another person yawn--is meant to cool down overheated brains.