Effects of attention to and awareness of preceding context tones on auditory streaming.

: This study determined whether facilitation of auditory stream segregation could occur when facilitating context tones are accompanied by other sounds. Facilitation was measured as the likelihood of a repeated context tone that could match the low (A) or high (B) frequency of a repeating ABA test to increase the likelihood of hearing the test as segregated. We observed this type of facilitation when matching tones were alone, or with simultaneous bandpass noises or continuous speech, neither of which masked the tones. However, participants showed no streaming facilitation when a harmonic complex masked the context tones. Mistuning or desynchronizing the context tone relative to the rest of the complex did not facilitate streaming, despite the fact that the context tone was accessible to awareness and attention. Even presenting the context tone in a separate ear from the rest of the harmonic complex did not facilitate streaming, ruling out peripheral interference. Presenting the test as mistuned or desynchronized tones relative to complex tones eliminated the possibility that timbre changes from context to test interfered with facilitation resulting from the context. These results demonstrate the fragility of streaming facilitation and show that awareness of and attention to the context tones are not sufficient to overcome interference.