The acquisition of grammatical morphemes, in particular that of the English regular past tense -ed, poses particular challenges for L2 learners. In contrast to L1 learners, even fairly advanced L2 learners sometimes produce sentences such as "John call me yesterday." Our research provides evidence for a phonology-based explanation to this problem.
Most accounts explain the lack of consistent tense marking as a gap in syntactic competence. Some researchers propose that functional categories responsible for tense are missing or impaired in the L2 grammar (e.g. Vainikka and Young-Scholten 1994/1996; Eubank 1993/1994), while others trace the problem to the mapping between underlying abstract features and surface forms (e.g. Prévost and White 1999/2000). Even though cross-language perceptual studies (e.g. Nathan 1987; Flege 1989) have revealed that adult L2 learners have considerable difficulty perceiving many non-native phonetic contrasts, few studies have explored the potential link between phonology and L2 tense marking (e.g. Wolfram 1985, Bayley 1994),
We report on a controlled experimental study of the effects of phonology on regular past tense marking in L2 English. Testing 68 L2 learners at two proficiency levels, we investigate whether the phonetic realization of the -ed morpheme - [t], [d] or [Id] - impacts learners' ability to perceive and produce it, in sentences like:

(1) The test started at eight.
(2) The young boy kissed a girl.
(3) The girl closed a window.

Our results show that L2 learners readily perceive the syllabic allomorph [Id], as in (1), but are significantly less able to perceive the non-syllabic allomorphs [t] and [d], as in (2), (3) [Syllabic: 88% correct; non-syllabic 63% correct; F(1,67)=238.4, p<.001]. Surprisingly, no significant difference is found between proficiency levels (high: 74% correct; low: 69% correct).
Results from a contextualized perception/production task, where participants could draw on grammatical and lexical knowledge in addition to perception, also show phonological effects. Both beginning and more advanced learners have difficulty perceiving the regular past tense morpheme, but advanced learners are able to compensate for this by using grammatical and lexical cues [high: 87% correct; low: 55% correct; F(1,65)=21.01, p<.001].
Our results suggest that L2 learners' inability to perceive the allomorphic variation of the past tense -ed morpheme is a barrier to producing it in a target-like manner, especially for lower level learners. We discuss the implications of these findings for theories of L2 syntax and L2 pedagogy.

Complete List of Presenters: Stephanie Solt, Yana Pugach, Elaine C. Klein, Kent Adams, Iglika Stoyneshka, Tamara Rose, Gita Martohardjono, Silvia Rivero