Intelligence measurement seems to me to be too focused on speed to be a good measure for everyone. I've never been very fast myself, but it doesn't limit the complexity or scope of what I can achieve. I haven't taken an IQ test since my teens, but at the time I remember being annoyed that I had to settle for a lower score than I felt I could have achieved simply because I ran out of time. A math tutor once told me he was a genius not because he could do something others couldn't, but because he could do the same steps very quickly. In my mind speed is one form of intelligence which can be very valuable, but it's a shallow measure. Particularly when judging student ability, speed can be a bad measure because students who are bored are often not remotely mentally engaged by the task at hand. That is where the grit factor comes in to play, by achieving the results even if it takes longer or proves more difficult in the focus and execution.