One interesting aspect of that is progress bars. Regardless of the amount of time an operation takes people will have a slightly different subjective opinion of

One interesting aspect of that is progress bars. Regardless of the amount of time an operation takes people will have a slightly different subjective opinion of how long it actually took depending on the behavior of the progress bar. Progress bars that slow down near the end seem to take longer than progress bars that accelerate near the end, even if the elapsed time is exactly identical.