One of the great puzzles of language acquisition has been described as poverty of the stimulus: how are complex aspects of language acquired when they appear to be rare or even non-occurring in the input that a learner receives and comprehends? This article presents an emergentist solution to one aspect of this puzzle (involving relative clauses) by examining the longitudinal development of meaningful discourse produced by Ana, a 12-year-old Spanish learner of English. Relative clause constructions are considered in terms of learnable, non-abstract linguistic analyses (lexicalist signs and constructions; dependencies), informed by emergentist syntax (O'Grady 2005), analyses within Head-driven Phrase Structure Grammar (Sag 1997), and a comprehensive corpus grammar (Biber et al. 1999). The data show that complex aspects of language gradually emerged from item-based and compositional learning processes that interacted with the learner's environment, including input frequency and the functional purposes for which language is used. Item-based, sign-based, and compositional analyses of constructions are valuable for syllabus design (for synthetic syllabi) and for the evaluation of language proficiency (i.e. testing and measurement).

This paper argues that the study of second language acquisition theory and pedagogy can be enhanced through the use of time-series research designs. As quasi-experiments, time-series designs have features that improve internal validity. In addition, because these designs only require a small number of subjects, they are very practical, encouraging a greater number of empirical investigations of the many claims within the field and permitting the use of authentic measures that have high construct validity. The longitudinal nature of the designs also enhances construct validity, potentially yielding new insights into the effects of instruction on SLA. The designs utilized in two time-series studies (Kennedy, E., 1988, The Oral Interaction of Native Speakers and Non-Native Speakers in a Multicultural Preschool: A Comparison between Freeplay and Contrived NS/NSS Dyads, unpublished master's thesis, University of British Columbia, Vancouver; Mellow, J. D., 1996, April, A Longitudinal Study of the Effects of Instruction on the Development of Article Use by Adult Japanese ESL Learners, unpublished manuscript, University of British Columbia, Vancouver) are reviewed in order to illustrate the design features, the questions that may be investigated, and the issues that are raised in interpreting data.

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A current limitation of the connectionist approach to second language acquisition (SLA) research is that it does not, to my knowledge, include complex linguistic representations. This article proposes a partial solution to this limitation by motivating and illustrating specific analyses that utilize the sign-based representations developed within Head-driven Phrase Structure Grammar (HPSG). To motivate the proposed representations, the article applies them to an analysis of four types of mappings between form and function: one-to-one, primed redundancy, nonprimed redundancy and polyfunctional. The paper summarizes representative SLA data that indicate how these mappings may appear in second language (L2) production. Key properties of HPSG analyses are discussed, indicating how they are consistent with connectionist assumptions. Sign-based representations of the four types of mappings are then provided, including several modifications to HPSG formalisms. The article concludes with a discussion of future directions.

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