Effects of pitch contour and speaking rate on perception of foreign-accented speech

Abstract

Perception of foreign accent is typically studied using an accentedness rating task. For example, native English listeners rate the degree of accentedness in sentences produced by non-native English speakers. However, in the past studies, it has been unclear that on what criteria participants used to judge accentedness. Here, native English speakers rated the accentedness of Korean-accented English sentences on a scale from 1 (strong accent) to 9 (little to no accent). Participants rated sentences that were unmodified or had one acoustic property removed. In one block, pitch contours of sentences were flattened and set to their mean values. In another block, speaking rates were set to the grand mean of all speaking rates (3.8 syllables/second). This way, changes in accentedness ratings across unmodified and modified sentences were attributable to the acoustic property that was removed. Accentedness ratings were not systematically influenced by manipulations of pitch contours but were influenced by speaking rate manipulations. Increasing the speaking rate (to 3.8 syllables/second) made sentences sound less accented than their unmodified versions; decreasing the speaking rate made sentences sound more accented than their unmodified versions. Results suggest that the speaking rate directly contributes to ratings of foreign accentedness.