Effects of differences in timbre on sequential grouping

Differences in the timbre of sounds in a sequence can affect their perceptu al organization. Using a performance measure, Hartmann and Johnson (1991) c oncluded that streaming could be predicted primarily by the extent to which sounds were passed by different peripheral channels. However, results from a rating task by Dannenbring and Bregman (1976) suggested that sounds in t he same spectral region (passed by the same peripheral channels) can be all ocated to different streams. In Experiment 1, it was found, using an interl eaved melody task, that target sounds could be selected from distracters in the same spectral region more easily when they differed in timbre. This fi nding might result from primitive stream segregation or schema-driven selec tion, but not from peripheral channeling. In Experiment 2, a rhythm discrim ination task was used, requiring the sounds to be integrated for good perfo rmance. Differences in timbre impaired performance, indicating the occurren ce of primitive stream segregation.