Effect of variability in level on forward masking and on increment detection

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal detection theory

Background:

• Forward masking is a phenomenon where a masker presented before a signal affects signal detection.
• Previous research suggests masker level can influence forward masking, but its precise role is debated.
• Understanding decision strategies in auditory tasks is crucial for explaining perception.

Purpose of the Study:

• To investigate the effect of masker level variability on forward masking thresholds.
• To determine if subjects employ an energy detection strategy in forward masking and increment detection tasks.
• To explore alternative decision models, such as template matching.

Main Methods:

• Four experiments were conducted using a two-interval forced-choice (2IFC) adaptive procedure.
• Varying masker levels across intervals and analyzing trial-by-trial data.
• Measuring performance using signal-to-noise ratio and d' in some experiments.
• Replicating findings with varied masker frequencies and in an increment-detection task.

Main Results:

• Varying masker level from interval to interval had minimal impact on forward masking thresholds.
• Subject performance was better when the masker in the signal interval was lower, independent of the nonsignal interval masker.
• Results were consistent across different masker variabilities and frequencies.
• Similar patterns were observed in an increment-detection task.

Conclusions:

• Decision processes in forward masking and increment detection are similar.
• These auditory tasks are unlikely to be based on a simple energy detection strategy.
• Template matching provides a plausible alternative explanation for the observed results.