Categorical processing of German vowel quantity.

Abstract

The present study investigates the behavioral and neural processing of duration in the German vowel /a/ using synthesized disyllabic nonsense words. The vowel /a/ was chosen since its long and short cognates are differentiated merely on the basis of vowel duration, unlike high and mid vowels which have additional differences in formant structure. By means of an identification test a sharp category border was found at 105.9 ms in theduration continuum from short to long category associated with a local peak in reaction time. Furthermore, an adaptive discrimination test applied to the entire continuum showed a minimum of the just-noticeable-difference for vowel duration at the category border. In an MEG study, the continuumof the disyllabic words was presented in randomized order. Besides two P50-M100 complexes in response to the first and the second syllable, the ERP data showed a secondary M100-like peak in case vowel duration exceeded the duration of the short category, which was not observed in a duration-matched nonspeech control condition. This secondary M100 might be interpreted as an additional phonological “event” or “slot”, indicating a nonlinear categorical difference in the processing across short and long vowels.