Frequency, Attention, and Phonetic Characteristics that Influence the Right-Ear Advantage for Speech Perception
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The right-ear advantage (REA) for linguistic stimuli (Kimura, 1961, 1967) is thought to represent an asymmetry of speech perception favoring the left hemisphere. This study seeks to clarify how the REA is altered by: attention instructions, filtering of stimuli, background noise, and phonetic properties of stimuli, viz., voice onset time (VOT) and place of articulation (POA). Participants heard monosyllabic rhyming words from the Halwes (1990) Fused Dichotic Word Test and were instructed to attend to the left or right ear, or to divide attention equally. Stimuli in Experiment 1 were unfiltered, high-pass filtered, or low-pass filtered, and stimuli in Experiment 2 were presented with no noise, white noise, high-pass filtered noise, or low-pass filtered noise. The initial consonants of each dichotic pair were categorized according to POA (bilabial, alveolar, or velar) and VOT (voiced or unvoiced). Repeated-measures ANOVAs performed on laterality ratios showed statistically significant main effects for attention, background noise, VOT, and POA. Right-ear attention, the absence of background noise, and bilateral bilabial presentation enhanced the right-ear advantage. Furthermore, attention interacted with background noise, POA, and VOT.