Effect of Speech-Sound Cue On Ear Asymmetry in Dichotic Listening

Under conditions of dichotic presentation, subjects were asked to identify (1) the vowels /i, e, o/ produced in isolation and in CV syllables, (2) the voiceless stops /p, t, k/ produced in CV syllables and from consonant-noise cues spliced from CV syllables, and (3) the voiced stops /b, d, g/ from consonant-noise cues and initial formant transition cues spliced from CV syllables and from final formant transition cues spliced from VC syllables. The same stimuli were also presented monaurally with continuous contralateral noise and monaurally with pulsed contralateral noise. Under the dichotic condition, right-ear advantages were found for stops identified from voiced consonant-noise cues (52.2 % v. 46.0%), from voiceless consonant-noise cues (71.2% v. 61.0% and from CV syllables (76.6% ν. 58.7%). The differences between ears were negligible for the vowel and formant transition stimuli. There was evidence of ear dominance under the pulsed contralateral noise condition which was similar to that found for the dichotic condition. Results did not support the encoded hypothesis that right-ear dominance is dependent on formant transition cues but did support the hypothesis that right-ear dominance increases as the similarity of the competing stimuli increases.