A two alternative forced-choice experiment (2 AFC) in which the observer is asked to state which is the larger of two segments of tones presented sequentially in time, is analyzed as an experiment involving only amplitude memory. Frequency, phase, starting time, and duration information is provided each trial by the stimuli. The 2 AFC experiment is conceived as one in which a measure of the intensity of the first signal serves to establish a cutoff value against which the measure of the second can be compared. If the measure of the second exceeds the cutoff then it is reported to be larger. If the measure of the second is less than the cutoff then the first is reported to be larger. The variable in these experiments was the time interval, τ, between the two signals. Intervals from 50 to 9600 milliseconds were studied. The efficiency in these experiments varied as the produce (1 − e−A τ)1/1 + A τ, where C is a damping constant and A is a constant describing the variance of the cutoff. (This study upon which this paper is based was sponsored by the Air Force Office of Scientific Research.)