title: The effect of stimulus intensity on the right ear advantage in dichotic listening.
abstract: The dichotic listening test is non-invasive behavioural technique to study brain lateralization and it has been shown, that its results can be systematically modulated by varying stimulation properties (bottom-up effects) or attentional instructions (top-down effects) of the testing procedure. The goal of the present study was to further investigate the bottom-up modulation, by examining the effect of differences in the right or left ear stimulus intensity on the ear advantage. For this purpose, interaural intensity difference were gradually varied in steps of 3 dB from -21 dB in favour of the left ear to +21 dB in favour of the right ear, also including a no difference baseline condition. Thirty-three right-handed adult participants with normal hearing acuity were tested. The dichotic listening paradigm was based on consonant-vowel stimuli pairs. Only pairs with the same voicing (voice or non-voiced) of the consonant sound were used. The results showed: (a) a significant right ear advantage (REA) for interaural intensity differences from 21 to -3 dB, (b) no ear advantage (NEA) for the -6 dB difference, and (c) a significant left ear advantage (LEA) for differences form -9 to -21 dB. It is concluded that the right ear advantage in dichotic listening to CV syllables withstands an interaural intensity difference of -9 dB before yielding to a significant left ear advantage. This finding could have implications for theories of auditory laterality and hemispheric asymmetry for phonological processing.
authors.affiliation: Department of Biological and Medical Psychology/Cognitive NeuroScience Group, University of Bergen, Norway. hugdahl@psybp.uib.no
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.forename: René
authors.initials: R
authors.lastname: Westerhausen
authors.forename: Kimmo
authors.initials: K
authors.lastname: Alho
authors.forename: Svyatoslav
authors.initials: S
authors.lastname: Medvedev
authors.forename: Heikki
authors.initials: H
authors.lastname: Hämäläinen
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001299:Audiometry / Q000379:methods; D001303:Auditory Cortex / Q000502:physiology; D001306:Auditory Pathways / Q000502:physiology; D004007:Dichotic Listening Tests / Q000379:methods*; D004423:Ear / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008144:Loudness Perception / Q000502:physiology*; D008297:Male; D010898:Pitch Perception / Q000502:physiology; D000091402:Prohibitins; D013017:Sound Localization / Q000502:physiology*