Lexical stress is an important contributor to foreign accent as well as intelligibility of second language (L2) speech. The present study intends to find out to what extent Chinese-speaking learners whose native language has less evident stress can acquire English lexical stress. A production test was administered to nine advanced Chinese learners of English and nine native English controls, who read aloud 12 types of nonce English nouns. The results showed that the Chinese participants were able to place stress correctly in two-syllable words and three-syllable words with a heavy penultimate syllable. However, irregularity was observed in three-syllable words with a light penultimate syllable, particularly H(eavy)L(ow)L(ow). The results are further interpreted in Optimality Theory. It is argued that the learners' interlanguage grammar is both negatively and positively influenced by their native language. The constraint only active in Chinese causes the interlanguage to be non-nativelike. By contrast, the shared active constraints facilitate learning. Moreover, the emergence of the constraints in the interlanguage grammar which are inactive in Chinese but active in English provides evidence for the learners' ability to restructure their interlanguage phonology.

Le is a functional morpheme in Mandarin, which can appear in two places, immediately after the verb (verb-le) or in a sentence-final position (sentence-le). Traditionally, verb-le is often referred to as a perfective aspect marker denoting completion, while sentence-le is generally considered as a sentence final particle which signals a change-of-state meaning. Based on Smith's aspect theory, which calls the grammatical aspect the viewpoint aspect and the lexical aspect the situation aspect, this paper argues that both les are perfective aspect markers derived from one super-le. Besides, it also compares le with guo, which is another post-verbal perfective aspect marker whose aspectual status has been well-established in the literature, and points out that guo differs from verb-le in that it always denotes the completion of event. It is further argued that the reason why le conveys distinct meanings lies in its position in the sentence. And thus, the conclusion is drawn as: although verb-le and sentence-le denote different meanings, they are essentially the same in terms of the three following aspects: (1) Both of them are perfective aspect viewpoint markers. (2) They have the same temporal interpretations. (3) They show the same variance from guo. Therefore, there is just one le which is a perfective aspect marker. If it is placed after the verb, it will have the terminative reading. If it is in the sentence-final position, it will form a Perfect and have a change-of-state reading. Given such difference, a syntactic representation of le in the clausal structure is proposed, in which verb-le is generated in the AspP lower within vP while sentence-le resides in the AspP adjoined to TP. The reason why guo cannot occur with verb-le is the different aspectual meanings they convey. Guo is concerned with the experience the subject has while sentence-le is about the state change.