Adults' perception and production of the English vowel /i/.

This study investigated the link between the perception and production of the English vowel /i/ by adult native speakers of English. Participants first produced the vowel /i/ using normal (citation) and careful (hyperarticulated) speech, then completed a method of adjustment task in which they selected their ideal exemplar of /i/. In this perceptual task, 24 of 35 participants had a prototype; the remaining 11 did not, but were retained for comparison. In keeping with the hyperspace effect (K. Johnson, E. Flemming, & R. Wright, 1993), all participants selected perceptual stimuli with F1 and F2 values that were more extreme (i.e., higher and further forward in the vowel space) than those of their normal, citation productions. An analysis of front-back and high-low qualities for the perceptual and production data in Euclidian space revealed that hyperarticulated speech was closer to the perceptual data than citation speech was, but only for participants with relatively clear-cut prototypes. The basis for such individual variation in perception-production links is discussed.

Adults' perception of native and nonnative vowels: implications for the perceptual magnet effect.

Two experiments were conducted to evaluate the perceptual magnet effect. In Experiment 1, American English speakers representing diverse dialects were presented with a fine-grained set of stimuli (varying in just noticeable differences for F1 and F2) and indicated whether they heard "/i/" or "not/i/," thus delimiting the /i/ portion of the vowel space for individual subjects. Then these same subjects selected their own /i/ prototype with a method-of-adjustment procedure. The data from this experiment were used to synthesize customized prototype and nonprototype stimulus sets for Experiment 2. In Experiment 2, 24 of our original 37 subjects completed a discrimination task for each of three conditions, in which vector stimuli varied from the subject's prototype, the nonprototype, or a foreign vowel (/y/) in 15-mel steps. Subjects displayed higher discrimination, as indexed by d', for the nonprototype condition than they did for both the prototype and the foreign conditions. In addition, discrimination was better for variants further away from the referent in each condition. However, discrimination was not especially poor for stimuli close to subjects' individual prototypes--a result that would have yielded the strongest support for the operation of a magnet effect. This negative finding, together with other aspects of our results, raises problems for any theory of vowel perception that relies solely on "one-size-fits-all" prototype representations.