Aims and Objectives: This article proposes the “scalpel model,” a new model of third and additional language (L3/Ln) acquisition. The model aims to identify and examine what happens beyond the initial state of acquisition and what factors may influence change from one state of knowledge to another. Methodology: The article briefly examines the currently proposed hypotheses and models and evaluates the existing evidence for their predictions. It highlights several cognitive and experiential factors affecting crosslinguistic influence that are not taken into account by the current models. These factors include: structural linguistic complexity; misleading input or lack of clear unambiguous evidence for some properties or constructions; construction frequency in the target L3; and prevalent language activation or use. Data and analysis: Findings of recently published research are discussed in support of the scalpel model. In particular, findings of differential learnability of properties within the same groups of learners suggest that L1 or L2 transfer happens property by property and is influenced by diverse factors. Findings: The scalpel model explicitly argues that wholesale transfer of one of the previously acquired languages does not happen at the initial stages of acquisition because it is not necessary. It also argues that transfer can be from the L1 or the L2 or both, but it is not only facilitative. Originality: The new model increases the explanatory coverage of the current experimental findings on how the L3/Ln linguistic representations develop. Implications: The model emphasizes the importance of the cognitive, experiential, and linguistic influences on the L3/Ln beyond transfer from the L1 or L2. Thus, it aligns L3/Ln acquisition with current debates within L2 acquisition theory.

It has been suggested that tense and aspect distributions are very difficult to learn in a second language (L2), they are prone to fossilize universally, and their interpretive properties are subject to a critical period (Coppieters, 1987). This study focuses on the acquisition of the semantic implications of the preterite-imperfect contrast in Spanish by English-speaking individuals of very advanced proficiency in Spanish who were not living in a Spanish-speaking country. By assuming that aspect is encoded in a functional category where the features [+/-perfective] are checked, depending on the language (Giorgi & Pianesi, 1997), this study asks whether ultimate attainment in the aspectual domain is possible and whether features of functional categories not selected in early childhood are subject to a critical period, as Hawkins and Chan's (1997) Failed Formal Features Hypothesis states. Experimental evidence from two tasks probing the interpretations of perfective and imperfective aspectual forms in Spanish suggests that many learners (almost 30%) in our total subject pool (including advanced to near-native speakers) and 70% of the near-native group performed like native speakers on all sentence types in all tasks. Although aspect is certainly a difficult area to master, particularly because the meanings of the imperfect are acquired quite late, L2 learners are clearly able to overcome the parametric options of their native language. At least for this domain, it is suggested that access to Universal Grammar does not necessarily decay with age in L2 acquisition.

This article has two main goals. The first is to summarize and comment on the current state of affairs of generative approaches to SLA (GenSLA), 35 years into its history. This discussion brings the readership of SSLA up to date on the questions driving GenSLA agendas and clears up misconceptions about what GenSLA does and does not endeavor to explain. We engage key questions, debates, and shifts within GenSLA such as focusing on the deterministic role of input in language acquisition, as well as expanding the inquiry to new populations and empirical methodologies and technologies used. The second goal is to highlight the place of GenSLA in the broader field of SLA. We argue that various theories of SLA are needed, showing that many existing SLA paradigms are much less mutually exclusive than commonly believed (cf. Rothman & VanPatten, 2013; Slabakova, Leal, & Liskin-Gasparro, 2014, 2015; VanPatten & Rothman, 2014)—especially considering their different foci and research questions.

Explaining why some linguistic features and constructions are easy or difficult to acquire in a second language has become a prominent current concern in generative second language acquisition (SLA) research. Based on a comparison of findings on the L2 acquisition of functional morphology, syntax, the syntax-semantics and syntax-discourse interfaces, the Bottleneck Hypothesis argues that functional morphemes and their features are the bottleneck of L2 acquisition; acquisition of syntax and semantics (and maybe even the syntax-discourse interface) flows smoothly (Slabakova 2006, 2008). The chapter presents recent experimental studies supporting this view. A pedagogical implication of this model is discussed, namely, that an enhanced focus on practicing grammar in language classrooms is beneficial to learners.