Identification of dichotic fusions

Seven synthetic syllables from a ’’place continuum’’ (/bae/–/dae/–gae/) were presented in all dichotic combinations for identification. These syllables fused completely, so that dichotic pairs were perceived as single stimuli. The response pattern could not easily be explained by an ’’auditory averaging’’ hypothesis. Rather, stimuli that were good instances of a category seemed to ’’dominate’’ stimuli that were closer to a category boundary. To account for this finding, a three-stage pattern recognition (’’prototype’’) model is proposed, according to which the information from the two ears is linearly combined after ’’multicategorical’’ processing, which follows auditory processing and precedes the final phonetic decision. Electronically mixed stimuli led to a response pattern that was similar to that for dichotic syllables (apart from some systematic deviations ascribed to peripheral masking), so that the same processes of central interaction seem to be involved. Average dichotic right-ear advantages of small magnitude were obtained for the dichotic fusions. They could not be reliably discriminated from binaural stimuli, and selective attention to one ear had little effect. With respect to the measurement of dichotic ear asymmetries, dichotic fusions offer certain methodological advantages over other dichotic stimuli. The problem of determining the ’’true’’ ear advantage is discussed. Subject Classification: [43]70.30; [43]65.75.