A lexical locus for the integration of asynchronous cues to voicing: An investigation with natural stimuli

Abstract

Speech perception requires integrating multiple asynchronous acoustic cues. Two questions pertinent to the integration of VOT and vowel length in word recognition were examined. First, this study asked whether lexical activation is sufficient to integrate these cues or if a sublexical buffer is required. Second, the role of stimulus type was examined since studies have found different results for synthetic and natural stimuli (Shinn et al., 1985; Miller and Wayland, 1993; Utman, 1998). An eye tracking methodology that is sensitive to timing and small differences in activation was used (McMurray et al., 2002). Stimuli were recordings of words (e.g., ‘‘beach’’ and ‘‘peach’’) whose initial VOT was manipulated along a nine-step continuum using splicing. The length of the following vowel was modified to create long and short vowels. Participants selected the correct object from screens containing the target, competitor, and two filler objects while eye movements were monitored. A small vowel length effect was found on voicing perception. This effect occurred substantially later in the fixation record than the effect of VOT. Thus, effects of vowel length can be seen in natural speech. Further, these cues each affect lexical activation as soon as they are available; no sublexical integration is required.