Just a personal observation, really, though one that as a student of human psychology fascinates me in other ways too.
There are pairings of actors that I get mixed up. For example: Al Pacino and Dustin Hoffman. Val Kilmer and Dennis Quaid. Several others.
I find though, that much of the time I can say, “Dennis Quaid…, no, the other one” and some one in the room says “Oh, you mean Val Kilmer.”
I find it fascinating, both that my mind works that way with it’s almost-not-quite-remember-that system and that the other person(people) in the room nevertheless know what I’m talking about.
Humans are endlessly fascinating, when they’re not being boorish, at least. 🙂