Morpho-phonotactic typicality and second language acquisition and processing

According to many accounts of word processing and access, an input word concurrently activates non-target lexical neighbours that become available for further processing stages. Psycholinguistic evidence shows how prediction andcompetition based on word similarity and lexical redundancy affect speakers' anticipation of incoming stimuli, so as to speed input recognition and improve lexical decision (Luce/Pisoni 1998; Bailey/Hahn 2001; Hahn/Bailey 2005, among others). As observed by Bailey and Hahn (2001), wordlikeness affects both language acquisition and processing. Wordlikeness can be defined in terms of phonotactic/ orthotactic likelihood and lexical density. Both neighbourhood size and frequency distribution of neighbours are known to play a role in word prediction and competition. In this perspective, monitoring this competing behaviour can shed some light on the relationship between phonotactic/orthotactic likelihood and lexical density, and their connection with issues of word recognition and production.My goal in this chapter is to provide a computational model of bilingual lexical self-organisation, with language-independent architectural and functional requirements of the lexical store, together with language-specific phonotacticconstraints, appearing to control aspects of interaction of first and second language (hereafter L1-L2) and define the propensity to acquire novel words, showing how acquisitional strategies are affected by past knowledge of languageand entrenched expectations on incoming stimuli.On the one hand, a strong expectation based on L1 affects the way L2 inputs are perceived. On the other hand, language-independent architectural and functional requirements of the lexical store, such as its highly integrated organisation andlanguage-non-selective access (Dijkstra/van Heuven 2002), appear to control aspects of L1-L2 interaction.Simulations in the neuro-computational framework of Temporal Self-Organising Maps (TSOMs, Ferro et al. 2011; Marzi et al. 2012, 2014a, 2016; Pirrelli et al. 2014, 2015), where word processing and lexical acquisition are implemented as recoding and storage strategies for time-series of symbolic units, will highlight how partially overlapping phonological representations may cause competition in incremental learning, and how weaker connections and recycledmemory resources make L2 representations underspecified due to the lack of strong lexical expectations and selective specialisation typical of the L1 representations.