Stimulus-based and task-based attention modulate auditory stream segregation context effects.

Previous studies have shown that perceptual segregation increases after listening to longer tone sequences, an effect known as buildup. More recently, an effect of prior frequency separation (Δ) has been discovered: presenting tone sequences with a small Δ biases following sequences with an intermediate Δ to be segregated into two separate streams, whereas presenting context sequences with a large Δ biases following sequences to be integrated into one stream. Here we investigated how attention and task demands influenced these effects of prior stimuli by having participants perform one of three tasks during the context: making streaming judgments on the tone sequences, detecting amplitude modulation in the tones, and performing a visual task while ignoring the tones. Results from two experiments showed that although the effect of prior Δ was present across all conditions, the effect was reduced whenever streaming judgments were not made during the context. Experiment 2 showed that streaming was reduced during the beginning of a test sequence only when participants performed the visual task during the context. These experiments suggest that task-based and stimulus-based attention differentially affect distinct influences of prior stimuli, and are consistent with the contribution of distinct levels of processing that affect auditory segregation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).