There are two measures of intelligence: Correctness and Speed. Correctness is the primary measure, and if two parties are correct then speed differentiates their level of intelligence. This is the only measure that has been quantified and scientifically correlated with many other attributes of human existence like success and happiness. This measure is is called IQ. If both people get an answer correct, then literall…
That said I'm pretty sure reaction time and "clock speed" are part of intelligence, just correlated well enough that you don't need a reflex test added onto the paper test.