Perceptual Asymmetry between Pitch Peaks and Valleys

Abstract

Perceiving pitch in spoken utterances is an important part of the speech comprehension process. Previous studies on pitch perception concentrated on ‘peaks’, neglecting ‘valleys’, thus making it difficult to know how generalisable the findings are. In two experiments, we took a factorial approach and contrasted the pitch movement direction associated with a stressed syllable (‘peaks’ vs. ‘valleys’), the turning point shape (sharp turn, 25 ms, 100 ms plateau), the accent height (varied in one-semitone steps), and pitch levels by shifting the whole contour up or down. We employed different sentences and also non-speech stimuli. Results showed that listeners were better at discriminating the pitch height between ‘peaks’ compared to ‘valleys’. In particular, ‘valleys’ in the low level posed challenges. A long pitch plateau forming a flat turn at a ‘peak’ or ‘valley’ made a ‘peak’ sound higher and a ‘valley’ lower compared to a sharp turn or short plateau of the same height. Moreover, similar results were observed across speech and non-speech stimuli. The perceptual asymmetry may lead listeners to allocate more attention to ‘peaks’ than ‘valleys’ in speech processing, while the effect of listeners’ native language deserves further investigation.