Relation between pitch shifts and MMF shifts in forward masking

Thresholds for brief sinusoidal signals were determined as a function of signal frequency for fixed sinusoidal maskers in a forward masking task. In some cases the frequency at which maximum masking occurred (MMF) was slightly above or below the masker frequency. In a second experiment subjects were required to adjust the frequency of the signals that its pitch matched that of the "masker." It was found that the frequency required for equal pitch correspond closely to the MMF. A possible explanation is that differences in quality between signal and masker (such as pitch differences) provide a cue for detection in forward masking which is not available when the signal and masker are very similar in quality. Thus maximum masking occurs when the signal and masker are most similar in quality.