Crossing of auditory streams.

The present experiment required subjects to judge the stream organization of patterns consisting of the elements of an ascending sequence of tones presented in rapid alternation with the elements of a descending sequence. The principle of grouping tones by their frequency proximity was found to dominate over the principle of grouping tones that follow a smooth trajectory. Therefore, subjects could not follow a sequence through its intersection in frequency with another sequence in a number of different tonal patterns. Differences of harmonic structure among the members of ascending and descending sequences allowed listeners to hear the sequences as crossing. The effects of rhythmic regularity and the slope and length of the tones themselves (when presented as short glides) were much less important. Several researchers (Bregman & Campbell, 1971; Dowling, 1973; Miller & Heise, 1950; and van Noorden, 1975) have encountered an interesting phenomenon in the course of investigating organizational processes in the perception of rapid acoustic sequences. It has been found that a rapidly presented sequence of alternating high and low tones tends to split perceptually into two sequences: one restricted