I work in a technical field, and possess a technical degree. But my ability to calculate relatively difficult in my head while on the run has gotten a lot better than it was even when I used my brain with some regularity in college.
For example, try to correlate how long it should take at a 7:40 mile pace to run what you believe to be 3/8ths of a mile can be difficult. After about 12 miles it can be nearly impossible as I slip into some catatonic state of monitoring my body only, not the feeble brain waves that are still bouncing around.
Even then, I manage to get close enough to know that my pace is right, or at least right enough. And that's what I'm after.
Then again, I could just ignore the watch except for the finishing time and get a heart monitor. But the last time I tried one of those I failed to get my heart rate under 165 and figured I was going to die at any moment, and that I'd rather not know that. You know, I thought just unknowingly falling down head over heels would be the best way. So I threw the monitor away.
And struggle with fractions. Ah yes, the glory of running.