When weak signals are presented in a background of continuous noise, the process of detection and the discrimination of a change in duration appears to be very similar. Two experimental techniques were used to investigate duration discrimination. The procedure in which the difference in duration between signals, ΔT, was varied given a fixed signal‐to‐noise ratio gave different results than the procedure in which signal amplitude was varied given a fixed ΔT. Although there were marked individual differences, all subjects roughly supported the general conclusion.