Insertion of discrete phonological units: An articulatory and acoustic investigation of aphasic speech

The traditional view that sound structure is mentally represented by discrete phonological units has been questioned in recent years. Much of the criticism revolves around the necessity of positing gradient or continuous sound structure representations to account for certain phenomena. This paper presents evidence in favour of discrete sound structure units in addition to gradient representations. We present a case study of aphasic speaker VBR, whose spoken language production errors include vowel insertions in many word-initial consonant clusters (e.g., bleed → [belid]). An acoustic and articulatory study is reported comparing the inserted vowels with lexical vowels in similar phonological contexts (e.g., believe). The results indicate that these two vowels come from the same population, suggesting discrete insertion of a unit the same size as those used to represent lexical contrast. The implications of these data for theories of sound structure representation are discussed.