Title: Multiplex model of mental lexicon reveals explosive learning in humans,
Abstract: Word similarities affect language acquisition and use in a multi-relational
way barely accounted for in the literature. We propose a multiplex network
representation of this mental lexicon of word similarities as a natural
framework for investigating large-scale cognitive patterns. Our representation
accounts for semantic, taxonomic, and phonological interactions and it
identifies a cluster of words which are used with greater frequency, are
identified, memorised, and learned more easily, and have more meanings than
expected at random. This cluster emerges around age 7 through an explosive
transition not reproduced by null models. We relate this explosive emergence to
polysemy -- redundancy in word meanings. Results indicate that the word cluster
acts as a core for the lexicon, increasing both lexical navigability and
robustness to linguistic degradation. Our findings provide quantitative
confirmation of existing conjectures about core structure in the mental lexicon
and the importance of integrating multi-relational word-word interactions in
psycholinguistic frameworks.