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 listenersÂ’ category expectations on speech perception.