Facepalm

Forgetting is part of our human nature. People forget things they've said, heard, or done though some of them have a method of calling back their thoughts. Some scrub or squeeze their head, others look aside and try to recall what's deep inside their mind, but very few of them use rough methods to express their failure to remember... Facepalm, or in other words, forehead slap. This common gesture either refers to annoyance or, in some cultures, forgetting.

I've been looking all over the internet for an explanation to this indication as a sign of disremember but I couldn't find anything. I'm looking it up because I'm afraid one of my friends is starting to develop some form of agnosia and with that he started to facepalm himself quite often or literally slapping his forehead to remember. His action started to look weird, unexplainable, and sometimes embarrassing to himself and those around him.

I know I won't be able to resolve his issue but at least I can read further more about it to convince him to see a doctor so if anybody has a point or a place to refer to please tell in the comments.