Perceiving vowels in isolation and in consonantal context.

Recent studies have shown that vowels tend to be identified more accurately in consonantal context than in isolation. This contextual advantage is often explained perceptually, e.g., by assuming that the formant transitions associated with the consonants convey significant vowel information. In two experiments with stylized synthetic speech patterns, we were unable to replicate the contextual advantage. These negative results were probably due to certain unnatural stimulus characteristics. In another experiment we used natural speech stimuli to assess whether nonperceptual factors associated with the identification task contribute to the contextual advantage. Subjects responded to the test items either by (a) circling written CVC syllables, (b) circling written isolated vowels, or (c) vocally mimicking the items (a task that we assume imposes minimal memory load on subjects). Of these response conditions, only the first yielded an advantage for vowels in context, suggesting that the effect depends on two factors: Stimulus-response compatibility and memory load.