Time : “Thusly, introverted people often measure large periods of time happening in very short periods of time, in relation to the measurements which might be derived if one were to focus on the outside world as a means of time measurement. Because of this, introverted people are prone to ‘losing track of time’, as they may perceive that, on a general basis, large amounts of time pass between events in ‘reality’ which most people would consider to be temporally significant but which they themselves would not find any significance, relative to their own perception of the passage of time. Therefore, introverted people are more likely to spend ages thinking about ‘something else’ and to not realize when a large amount of time has actually passed in terms of a system of temporal measurement they have no interest in maintaining. If a large amount of time spent thinking is equal to a short amount of time in ‘outside reality’, then it becomes difficult to distinguish at which point a large amount of time has transpired in ‘reality’ without counting, equating and making differences with the apparent time-frame of outside reality. However, no experiments confirm or discount this hypothesis so far.”

[Wikipedia scares me. You can follow links forever and still keep going on to new things. My head hurts.]