What speeds up the internal clock? Effects of clicks and flicker on duration judgements and reaction time

Four experiments investigated the effect of pre-stimulus events on judgements of the subjective duration of tones that they preceded. Experiments 1 to 4 used click trains, flickering squares, expanding circles, and white noise as pre-stimulus events and showed that (a) periodic clicks appeared to "speed up" the pacemaker of an internal clock but that the effect wore off over a click-free delay, (b) aperiodic click trains, and visual stimuli in the form of flickering squares and expanding circles, also produced similar increases in estimated tone duration, as did white noise, although its effect was weaker. A fifth experiment examined the effects of periodic flicker on reaction time and showed that, as with periodic clicks in a previous experiment, reaction times were shorter when preceded by flicker than without.