We recently tried out the use of intentional yawning as part of a guided meditation here at the Wilmington VA's MBSR Graduate group (Mondays room 7070, 9:30-12:30). We have reviewed and written about the science behind the power of yawning to activate a center of the brain, the Precuneus, elsewhere here. However, as those citations are scattered in different parts of this forum, please find below links to all of it, as well as a link to Dr Andrew Newberg's website. He is local to Philadelphia.
Source references for 'Precuneus Meditation, June 25, 2018: