both relaxation and heightened cognitive awareness. It helps you stay focused, as well as more introspective and self-aware. Waldman says that studies of deliberate yawning at Moorpark College are producing surprising results. Students who yawned before taking tests raised their grade point averages; C’s moved up to B’s, and B’s to A’s. He also asks his "profoundly anxious" therapy clients to yawn and has found that it reduces their anxiety by a significant amount.
Source: Science of Mind