Tap and trill clusters in typical and protracted phonological development: Challenging segments in complex phonological environments. Introduction to the special issue.

The papers in this crosslinguistic issue address children's acquisition of word-initial rhotic clusters in languages with taps/trills, that is, the acquisition of challenging segments in complex environments. Several papers also include comparisons with singleton rhotics and/or /l/ as a singleton or in clusters. The studies are part of a larger investigation that uses similar methodologies across languages in order to enhance crosslinguistic comparability (Bernhardt and Stemberger, 2012, 2015). Participants for the current studies were monolingual preschoolers with typical or protracted phonological development who speak one of the following languages: Germanic (Icelandic/Swedish); Romance (Portuguese/Spanish); Slavic (Bulgarian/Slovenian) and Finno-Ugric (Hungarian). This introductory paper describes characteristics of taps/trills and general methodology across the studies, concluding with predicted patterns of acquisition. The seven papers that follow are in a sense the 'results' for this introduction. A concluding paper discusses major findings and their implications for theory, research and clinical practice.