Effects of stress on intervocalic stop lenition in American English

Descriptions of English and other languages have claimed that intervocalic stops are often lenited to fricatives or approximants in connected speech, but relatively few acoustic analyses of factors that affect lenition have been reported for American English (cf. Lavoie 2001, Warner and Tucker 2011). In this analysis, intervocalic voiced stops produced in bi- and trisyllabic words during story reading are examined (participants N=13). The first result shows that American English speakers never lenite to fricatives, but rather produce approximants whenever lenition occurs. Second, stress plays an essential role: 51% of stops are lenited when stress is on the first syllable (e.g. "yoga"), but only 7% of stops lenite when stress is on the second syllable (e.g. "lagoon"). Overall, approximant productions are significantly higher for /d/ and /g/ as compared to /b/. For both stress placements, stop productions are longer and lower in intensity than approximant productions. These acoustic findings are partially consistent with Kingston's (2007) claim that lenition occurs to minimize interruptions to the prosodic unit and indicate that the current constituent is ongoing, but speakers may also use full and reduced stop variants to enhance cues to lexical stress.