Models and dynamics of the morphological lexicon in mono- and bilingual acquisition

Aim of this work is to define an explanatory model of the morphological lexicon as a dynamic system of word acquisition and storage in both mono- and multi-lingual contexts. The main focus is on exploring some aspects of the paradigmatic organisation of the mental lexicon in language acquisition, based on a dynamic analysis of mono- and bilingual contexts. An interdisciplinary approach to the lexical acquisition combines theoretical-motivated accounts, psycho-cognitive evidence and methodologies, and machine learning technologies. In particular, the thesis deals with those basic psychological and cognitive mechanisms considered as crucial in language acquisition: (i) the ability to perceive recurrent morphological structures (invariances) in varying temporal contexts, (ii) the capability to access/activate time series of symbols in the short term memory and to selectively integrate them with long term memory expectations, (iii) the attitude towards building novel forms through analogical extension of intra- and inter-paradigmatic relations (generalisation). This investigation is pursued through a computational model based on Self-Organising Maps with Hebbian connections defined over a temporal layer (Temporal Self-Organising Maps - TSOMs), providing a principled algorithmic account of effects of lexical acquisition, processing and access. Computational simulation of biologically inspired neural architecture of the mental lexicon offers the possibility to reproduce a wide range of conditions of mono- and multi-lingual input exposure, and to illustrate the dynamic of word acquisition and the emergence of morphological organisation. The proposed model provides an adaptive multifactorial account of morphology acquisition affected by input factors, such as word frequency distributions, paradigm regularity and wordlikeness, whereby lexical perception and organisation are grounded on memory-based processing strategies.