Criterion shifts in the measurement of tactile masking

A series of experiments was conducted to determine the effects of method of threshold measurement on the amount of threshold shift produced by a masking stimulus. The amount of contralateral tactile masking of the fingertip was found to be much greater when thresholds were measured by the Békésy tracking method than when measured by a forced-choice method. When the Békésy tracking procedure was modified so that each observation interval containing a brief stimulus was followed almost immediately by a second observation interval not containing a stimulus, the amount of masking was substantially reduced for both contralateral tactile masking and auditorytactile masking and corresponded almost exactly with the amount of masking measured by the forced-choice method. No such reduction in the amount of masking was obtained by using this procedure to measure ipsilateral tactile masking or auditory masking.