Despite extensive research on language acquisition, our understanding of how people learn abstract linguistic structures remains limited. In the phonological domain, we know that perceptual reorganization in infancy results in attuning to native language (L1) phonetic categories and, consequently, in difficulty discriminating and learning non-native categories. This difficulty has been proposed to originate from novel sounds being perceptually mapped onto L1 phonetic categories, leading to massive L1 interference. However, ample evidence that the adult speech processing system preserves a considerable degree of plasticity suggests that more complex learning mechanisms might be in place. In this dissertation I propose an alternative theory in which non-native speech processing is guided by principles of hierarchical inductive inference regarding how likely a given phonetic dimension is to be phonologically informative in any novel language. This theory differs crucially from mapping theories in predicting that when a phonetic dimension is informative (e.g., phonologically contrastive) in one's native language, discriminations involving that dimension should be enhanced even among classes of sounds for which the dimension is not informative in the native language. I provide experimental evidence supporting the inductive theory, demonstrating that language learning goes beyond the acquisition of specific phonetic categories, and includes higher-order generalizations regarding the relative importance of phonetic dimensions in the language as a whole. I argue that this theory can be extended beyond phonetic category learning to other domains of language acquisition, and that it suggests that adults and infants recruit the same domain-general learning mechanisms when acquiring novel languages

Baković (2005) analyzes the avoidance of ‘sufficiently similar’ adjacent consonants as the interaction of independent antigemination and assimilation processes. We present evidence from the phonology of monoconsonantal proclitics in Polish in support of the primary consequence of this analysis, that any conditions on antigemination or assimilation will also be conditions on ‘sufficient similarity’ avoidance. These conditions concern the segmental contexts in which geminates are disallowed in Polish and the variability of one of the assimilation processes involved. The analysis is further corroborated by the coincidence of two changes in progress: as the rate of variable assimilation has gone down, so has the rate of ‘sufficient similarity’ avoidance.

How are languages learned, and to what extent are learning mechanisms similar in infant native-language (L1) and adult second-language (L2) acquisition? In terms of vocabulary acquisition, we know from the infant literature that the ability to discriminate similar-sounding words at a particular age does not guarantee successful word-meaning mapping at that age (Stager & Werker, 1997). However, it is unclear whether this difficulty arises from developmental limitations of young infants (e.g., poorer working memory) or whether it is an intrinsic part of the initial word learning, L1 and L2 alike. In this study, we show that adults of particular L1 backgrounds-just like young infants-have difficulty learning similar-sounding L2 words that they can nevertheless discriminate perceptually. This suggests that the early stages of word learning, whether L1 or L2, intrinsically involve difficulty in mapping similar-sounding words onto referents. We argue that this is due to an interaction between 2 main factors: (a) memory limitations that pose particular challenges for highly similar-sounding words, and (b) uncertainty regarding the language's phonetic categories, because the categories are being learned concurrently with words. Overall, our results show that vocabulary acquisition in infancy and adulthood shares more similarities than previously thought, thus supporting the existence of common learning mechanisms that operate throughout the life span. (PsycINFO Database Record