I'm curious as to why people scratch their heads when thinking about a problem?

Because, tragically, scratching your genitals whilst pondering is frowned upon.

I have only ever seen it done in movies, TV shows etc., never once in real life.

A lot of our communication is non-verbal.
I’d assume the purpose of head-scratching is to display to others that you’re trapped in thought.

I think that for the most part, it’s just a generalized gesture for thinking, but I have actually never done it/never seen anyone do it in real life.

I do this all the time. I actually did while thinking about how to respond to this question.

I think I do because it is my subtle way of saying “STFU, I am thinking.”

Don’t know. When I’m thinking, I don’t really scratch my head, but I do rest my chin in my hand or rub my upper lip or nose with my fingers. Weird.

Different parts of the brain firing up (when one is thinking of different things) and causing a localised response (electro-muscular), which then registers (semi-consciously) as a slight vibration around and area of cranial skin and hair. Unknowingly, we then have a scratch.

Or something like that, perhaps.

I have found that it actually helps me relax for a second while I gather my thoughts…I know that sounds weird, but i imagine unconsciously thats why we do it…if people do it of course.

I have never seen anyone do that.

I don’t scratch my head, but I very often do bring my hands up to my head in some other way (putting a finger or my hand over my lips seems to be a common one).

To me, this feels like a way of closing out the world for a moment and folding myself inward. It feels like I’m creating a more private space for myself.

I think this is just the gesture we most associate with thinking (or really, questioning). Another very common gesture associated with thinking (or perhaps, pondering) is stroking one’s chin/beard. Another common gesture or fidget I’ve noticed since getting married is folks playing with their wedding rings (or bracelets, watches, etc).

I think it’s all akin to doodling, a gesture of another type associated with clearing one’s mind, thinking deeply (or ironically, zoning out).

Hmmmh…(scratches head)....thinks…(don’t know)