Forward and backward masking with brief impulsive stimuli

The forward and backward masking effect of a 20-micros pulse was measured for delays ranging from 0 to -/+4 ms. Masking is not a monotonic function of delay in either forward or backward masking. For two of the three observers, the asymmetry in which forward masking exceeds that of backward masking is small for delays less than 500 micros. The implications of the data for the contribution of masking to the precedence effect are considered.