If you've ever written code before, you've experienced "code head." If previous statement is true, and you've been in a relationship with someone else, then they've experienced you with "code head." If you string together sentences with operators like "and," "or," "not," "true," and "false," then you've experienced "code head."
It's not like a cold you can catch, or some disease, but it is a state of mind that impacts the people around you when you have it. It's the result of being heads-down in programming, math, or data analysis long enough that your brain continues to loop and process logic problems long after you've left the keyboard. Guess what!? If you have "code head" you're generally not fun to be with until it goes away.
If you're around others (say back home with the family, or out to happy-hour with friends) with "code head," it's obvious, and you aren't interacting with everyone else the way you do when you don't have "code head." You appear sluggish, and detached (because you ARE), and there's an impedance mismatch between you and everyone else.
If you find yourself around someone with "code head," either break off and re-engage at a later date, or help them get out of it by piquing their interest in another topic. NOTE: the latter can be very difficult.
Hmmm, is this a long way of describing someone being distracted? Oh well... my friend Ingrid used the term "code head" today, and I was compelled to write about it.