Abstract
The build-up of auditory stream segregation refers to the notion that sequences of alternating A and B sounds initially tend to be heard as a single stream, but with time appear to split into separate streams. The central assumption in the analysis of this phenomenon is that streaming sequences are perceived as one stream at the beginning by default. In the present study, we test the validity of this assumption and document its impact on the apparent build-up phenomenon. Human listeners were presented with ABAB sequences, where A and B were harmonic tone complexes of seven different fundamental frequency separations (Δf) ranging from 2 to 14 semitones. Subjects had to indicate, as promptly as possible, their initial percept of the sequences, as either “one stream” or “two streams,” and any changes thereof during the sequences. We found that subjects did not generally indicate a one-stream percept at the beginning of streaming sequences. Instead, the first perceptual decision depended on Δf, with the probability of a one-stream percept decreasing, and that of a two-stream percept increasing, with increasing Δf. Furthermore, subjects required some time to make and report a decision on their perceptual organization. Taking this time into account, the resulting time courses of two-stream probabilities differ markedly from those suggested by the conventional analysis. A build-up-like increase in two-stream probability was found only for the Δf of six semitones. At the other Δf conditions no or only minor increases in two-stream probability occurred. These results shed new light on the build-up of stream segregation and its possible neural correlates.
Highlights
In recent years, the perceptual phenomenon of auditory stream segregation, i.e., the decomposition of a mixture of sounds into meaningful objects or streams, has been extensively investigated.In laboratory experiments, the mixture generally consists of A and B sounds, which differ in some specific characteristic(s), most often in frequency
The present study tested the assumption of a default one-stream percept at the beginning of streaming sequences prevalent in the conventional analysis and elucidated its consequences for the analysis of the build-up phenomenon
The first perceptual decision depended on the frequency separation between A and B sounds
Summary
The perceptual phenomenon of auditory stream segregation, i.e., the decomposition of a mixture of sounds into meaningful objects or streams, has been extensively investigated. Current research on auditory stream segregation focuses on the stimulus characteristics sufficient for stream segregation to occur (for review, see Moore and Gockel, 2002), on the underlying neural www.frontiersin.org mechanisms in different species including humans (for recent reviews, see Carlyon, 2004; Micheyl et al, 2007; Snyder and Alain, 2007; Bee and Micheyl, 2008; Shamma and Micheyl, 2010), on the development of conceptual and computational models accounting for psychophysical and physiological data (Hartmann and Johnson, 1991; Beauvois and Meddis, 1996; Denham and Winkler, 2006; Winkler et al, 2009; Shamma et al, 2011), and on the temporal dynamics of auditory stream segregation The latter includes the build-up of stream segregation (Bregman, 1978; Anstis and Saida, 1985; Cusack et al, 2004; Micheyl et al, 2005; Pressnitzer et al., 2008; Bee et al, 2010; Haywood and Roberts, 2010) and the percept stability (Pressnitzer et al, 2008; Bendixen et al, 2010; Kondo et al, 2012; Denham et al, in press). Our results shed new light onto the build-up phenomenon
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
