Vibrotactile forward masking: effects of the amplitude and duration of the masking stimulus

Tactile thresholds for detecting a 50-ms signal presented 25 ms after the termination of a masking stimulus increased as a function of the amplitude level and duration of the masking stimulus. The effects were similar in both the P and NP I channels measured at 250 and 20 Hz, respectively. It was concluded that the increased masking caused by increasing the duration of the masking stimulus resulted from processes other than or in addition to temporal integration--the latter being a characteristic of the P, but not the NP I, channel. The slopes of the masking functions, in which threshold shifts were plotted as a function of masking-stimulus sensation level, were consistently greater for 20-Hz than for the 250-Hz stimuli, suggesting that masking efficiency is greater in the NP I than in the P channel.