Sense of humor and grammar, I would agree. Intelligence and analytical reasoning ability, not in my experience. People who are truly gifted recognize it, and so do their peers. People who don’t have the smarts to be in the field (math, physics, engineering) realize they are struggling and so do those who work with them.
I think there was an earlier study which showed that smart people initially don’t think they’re smart, until they see what dumb people are like and then they know they’re smart. lol