What's up with not being able to use your skills when someone is watching?

You can tell the scientific reason or just share your experience with the subject it's really fun to read always.

I come up with pretty clever names and ideas when programming but if someone is watching best I can do is muscle memory.

If I wrote an essay while someone else is watching it would look like a middle-schooler wrote it.

Same situation when I am in an exam room with 5 other people is completely fine.

Hell I used to work at a warehouse but I attempted to tape a box the sticky part up one time because the supervisor is watching.

He just looked tired after seeing tip of the tape get dragged across a box like some cat toy.

Is it magic?