Phonological regressions or U-shaped development have frequently been observed in longitudinal studies of child speech production. However, the typology of which phonological patterns regress, and their implications for learning, have not been given much attention in the recent literature on constraint-based phonological development. One basic question is simply the definition of a phonological regression, as created by the grammar or other mechanisms, which is in turn dependent on the type of grammar and learner assumed. This paper systematically addresses the question of whether or not attested phonological regressions are incompatible with an error-driven approach to grammatical development, whereby each round of learning is predicted to move the learner closer to the target language. From this perspective, this survey discusses case studies of phonological regression in the literature, grouped according to their ease of explanation under error-driven learning. Three types are identified and exemplified: regressions which are easily explained with existing error-driven algorithms for constraint-reranking; regressions which can also be derived through error-driven learning by adopting an additional tool (for incorporating child-specific phonetic experience); and regressions whose error-driven motivation remains unclear. Another central theme of the survey is the degree of variation and lexical exceptionality among these regression patterns, and the extent to which such variability is captured in the learner's algorithms or grammar. Interim conclusions are provided, and necessary future directions for empirical and theoretical research are discussed. This article is categorized under: Linguistics > Language Acquisition Linguistics > Linguistic Theory.
Keywords: constraint-based grammar; learning algorithms; phonological acquisition; regressions.
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