"I have a married friend who has part of his brain 'always on the prowl'."I think a large amount of people are similar, continually evaluating compatibility/outward signs and actions, at least at some level consciously. I've definitely had friends talk about it, especially when working out a lot- noticing fitness and visual appearance, gestures, tones, poses, 'energies', status, availability. I have a married friend who has part of his brain 'always on the prowl'.
Honestly I don't really think that way, and I sometimes feel rather weird as a guy. I can be very task focused, though, or completely lost in other thoughts when out. Literally just got my testosterone tested last week, 729, so doesn't seem like that is off. Also my relationships certainly don't miss out any in that regard. Sort of like a mode switch or something.
But yeah, you don't sound abnormal if you are getting what you need done.
Does his wife know his brain is "always on the prowl"? That means he's opening himself up to the possibility of another woman. I feel sorry for his wife. I don't know why some men can't just be satisfied with what they have. Men who are in a relationship, but always looking over their shoulder for the next best thing deserve nothing.