Contribution of pitch-accent information to lexical decision in Japanese

Abstract

Word intelligibility, latency in shadowing, and brain activations when listening to spoken Japanese with incorrect pitch accents compared to normal, were investigated. Japanese is one of pitch-accent languages. In a pitch-accent language, “where” the pitch falls is important, whereas in Mandarin Chinese “how” pitch rises and falls is important. The word intelligibility scores were examined based on the adequacy rating of the accent types. Results reveal that under noisy conditions, the higher the adequacy of the accent type was rated, the higher the word intelligibility was. Under the clean condition, a significant negative correlation was shown between latency in shadowing and adequacy rating of accent types. In the event-related fMRI experiment, brain activities were investigated when listening to words with incorrect pitch accents (INCORRECT condition) and words with normal pitch accents (NORMAL condition). The contrast between INCORRECT and NORMAL revealed the significant activation in the bilateral inferior frontal, the bilateral precentral, and the left supplementary motor area, and right superior temporal gyrus. The result support the view that speech perception is a sensory-motor process, suggesting when a pitch accent of the stimulus was mismatch to the template, silent rehearsal might be repeated to make a lexical decision.