To identify the neural correlates of yawn contagion, we
acquired functional MR images from 30 adult volunteers who
watched videotaped sequences of yawns and control stimuli. The
subjects were instructed to attentively view the faces but yawning
was not mentioned in any way. The subjects were prevented from
overt yawning by constraining their heads and chins to avoid
movement artifacts. The effectiveness of these constraints was