The present study was designed to investigate how well listeners are able to unambiguously categorize an unstressed vowel in a word as either a full vowel or a schwa. It was found that listeners disagree in many cases on the assignment of a vowel to either of these categories. This suggests that listeners cannot properly distinguish between acoustic reduction (the loss of spectral quality of a full vowel) and lexical reduction (the substitution of a full vowel with a schwa). Other points of interest in the present study were the frequency of occurrence of words and speech styles; both were found to have a considerable influence on the process of vowel reduction.

Keywords: Vowel reduction, vowel categories, frequency of occurrence of words, speech styles.