The meanings of various lengths of elapsed time do not vary widely from one person to another:
Less than 1/3 sec is ‘instantaneous’,
Less than l sec is ‘fast’
Less than 5 sec is a ‘pause’ and
Greater than 10 sec is a ‘wait’.
Time sharing interactions should be ‘instantaneous.’ Transaction interactions should be without ‘wait.’

- Jones - in For Principles of Main Computer Dialog Computer Aided Design, Vol. 10, No. 3, pg 197, May 1978