Postrecognition of interleaved melodies as an indirect measure of auditory stream formation

Primitive processes involved in auditory stream formation are measured with an indirect, objective method. A target melody interleaved with a distractor sequence is followed by a probe melody that was identical to the target or differed by 2 notes. Listeners decided whether the probe melody was present or not in the composite sequence. Interleaved melody recognition is not possible when distractor sequences have the same mean frequency and maximum contour crossover with target melodies. Performance increases with mean frequency separation and timbral dissimilarity and is unaffected by the duration of the silent interval between composite sequence and probe melody. The relation between this indirect task measuring the interleaved melody recognition boundary and direct judgments measuring the fission boundary is discussed. The everyday auditory environment consists of multiple, simul-taneously active sources with overlapping temporal and spectral acoustic properties. Despite the seemingly chaotic composite sig-nal impinging on people’s ears, the resulting perception is of an orderly “auditory scene ” that is organized according to sources and auditory events. Individuals are thus able to follow speech in