Phonemic Transformations: Mapping the Illusory Organization of Steady-State Vowel Sequences

Previous research has shown that listeners presented with repeated sequences of brief steady-state vowels (30–100 msec) experience phonemic transformations (that is, illusory changes in the identity of the constituent speech sounds) and report hearing verbal forms consisting of one or more syllables rather than a succession of vowels. Often the signal is split perceptually into two simultaneous organizations differing in both timbre and phonemic content. The present studies employed sequences of eight 80-msec vowels and mapped the perceptual phonemes to acoustic phones by terminating the repeated sequence at predetermined positions and determining the last speech sound heard in the perceived verbal organization (Experiments 1 and 2). When two simultaneous organizations were heard, they were both mapped (Experiments 2 and 3). It was found that: (1) all listeners reported hearing a polysyllabic verbal organization together with either a noise-like non-linguistic residue or a second verbal organization; (2) the verbal forms heard not only followed the phonotactic rules of English, but also corresponded to syllables actually found in English; (3) when two simultaneous organizations were heard, the primary or more salient one was usually longer; (4) simultaneous organizations had different timbres. Implications concerning the perceptual organization of speech are discussed.