Forehead tapping: the subtle dance of tapping one's forehead with the fingers, usually in a rhythmic pattern, to convey deep thought, emphasis, or, more often than not, to signal "I am a functioning member of society."
There are many methods to this tapping madness, but here are some of the most popular:
Disclaimer: Forehead tapping may not be suitable for all situations. Please exercise caution and consider the context before engaging in this potentially hazardous activity.