In designing the two-tier answer system for GameBrain, it was obvious that correct fill-in-the-blank answers had to be worth more than correct multiple-choice answers because they are much harder. However, when we decided to incentivize faster multiple-choice answers by reducing the value of a correct answer by as much as fifty percent if the maximum amount of time (10 seconds) was utilized, this raised the question of whether we should apply the same point-reduction to the fill-in-the-blank answers as well.
However, we ultimately decided against that, because it would give an advantage to players who read faster and type faster. Reading faster isn't much of an advantage in multiple choice because the question has already been read and the timer starts anew when one moves from FIB to MC. But typing faster is a big advantage, particularly when there could be a 12-point difference in six seconds. So, we decided to keep a flat point reward for fill-in-the-blank no matter what portion of the 12 seconds is used, and start the penalty gradient for multiple choice at the 3-second mark.
This playtests well, and the only potential issue that remains is if there should be any penalty for waiting most of the 12 seconds one has to do FIB before hitting the spacebar and moving to multiple choice.