The interrelation between the stimulus range and the number of response categories in vowel categorization

We investigate the influence of the stimulus range and the number of response categories on the location of perceptual boundaries. The F1 continuum between Spanish /i/ and /e/ was presented to Peruvian listeners in three ranges. Half of the listeners could classify the tokens as /i/ and /e/, the other half chose from the five Spanish vowels. A boundary shift between /i/ and /e/ was observed as a function of the stimulus range, which was larger when listeners were given only two response categories. These results are interpreted as an effect of listeners’ category expectations on speech perception.