This commentary discusses Westergaard's (2021) keynote article, which presents a comprehensive model of first language (L1), second language (L2), and third language (L3) acquisition. The commentary presents evidence from a previous study of L3 learners that provides support for Westergaard's property-by-property transfer proposal. The commentary…

The Bottleneck Hypothesis argues that properties of inflectional morphology explain why second-language learners may face persistent difficulties in articulating meaning in target-language forms. In particular, the acquisition task proves even harder when first and second languages differ in the way they organize the mapping of functional features…

A review of research about second language learning indicates that nonprimary acquisition is sensitive to the center-periphery distinction. There is clear evidence that this construct has reflexes in interlanguage word order with respect to the probability of native word order influence, difficulty, and order of emergence. (CB)