Robust Language Acquisition – an Emergent Consequence of Language as a Complex Adaptive System

Robust Language Acquisition – an Emergent Consequence of Language as a Complex Adaptive System Nick C. Ellis (NCELLIS@Umich.Edu) Department of Psychology and English Language Institute, University of Michigan 1085 South University Ave., Ann Arbor, MI 48109-1107 USA Matthew Brook O’Donnell (MBOD@Umich.Edu) English Language Institute, University of Michigan 1085 South University Ave., Ann Arbor, MI 48109-1107 USA Abstract the examples you have heard. Mandool inherits its interpretation from the echoes of the verbs that occupy this VAC – words like come, walk, move, ..., scud, skitter and flit - in just the same way that you can conjure up an idea of my dog Phoebe, who you have never met either, from the conspiracy of your memories of dogs. Knowledge of language is based on these types of inference, and verbs are the cornerstone of the syntax- semantics interface. To appreciate your idea of Phoebe, we would need a record of your relevant evidence (all of the dogs you have experienced, in their various forms and frequencies) and an understanding of the cognitive mechanisms that underpin categorization and abstraction. In the same way, if we want a scientific understanding of language knowledge, we need to know the evidence upon which such psycholinguistic inferences are based, and the relevant psychology of learning. These are the goals of our research. To describe the evidence, we take here a sample of VACs based upon English form, function, and usage distribution. The relevant psychology of learning, as we will explain, suggests that learnability will be optimized for constructions that are (1) Zipfian in their type-token distributions in usage (the most frequent word occurring approximately twice as often as the second most frequent word, which occurs twice as often as the fourth most frequent word, etc.), (2) selective in their verb form occupancy, and (3) coherent in their semantics. We assess whether these factors hold for our sample of VACs in a large corpus of usage. Parallel psycholinguistic experiments demonstrate the psychological reality of these constructions in language users. Each of us as learners had different language experiences, yet we have converged on broadly the same language system. From diverse, noisy samples, we end up with similar competence. How so? Some views hold that there are constraints in the learner’s estimation of how language works, as expectations of linguistic universals pre-programmed in some innate language acquisition device. Others hold that the constraints are in the dynamics of language itself – that language form, language meaning, and language usage come together to promote robust induction by means of statistical learning over limited samples. The research described here explores this question with regard English verbs, their grammatical form, semantics, and patterns of usage. Analyses of a 100-million-word corpus show how Zipfian scale-free distributions of usage ensure robust learning of linguistic constructions as categories: constructions are (1) Zipfian in their type-token distributions in usage, (2) selective in their verb form occupancy, and (3) coherent in their semantics. Parallel psycholinguistic experiments demonstrate the psychological reality of these constructions in language users. Keywords: Language as a Complex Adaptive System, Zipf’s law, Verb Argument Constructions; Syntax-semantics interface; Usage-based models. Verb Argument Constructions in Usage, Acquisition, and Mind As a child, you engaged your parents and friends talking about things of shared interest using words and phrases that came to mind, and all the while you learned language. We were privy to none of this. Yet somehow we have converged upon a similar-enough ‘English’ to be able to communicate here. Our experience allows us similar interpretations of novel utterances like “the ball mandoolz across the ground” or “the teacher spugged the boy the book.” You know that mandool is a verb of motion and have some idea of how mandooling works – its action semantics. You know that spugging involves transfer, that the teacher is the donor, the boy the recipient, and that the book is the transferred object. How is this possible, given that you have never heard these verbs before? Each word of the construction contributes individual meaning, and the verb meanings in these Verb-Argument Constructions (VACs) is usually at the core. But the larger configuration of words carries meaning as a whole too. The VAC as a category has inherited its schematic meaning from all of Construction grammar and Usage Constructions are form-meaning mappings, conventionalized in the speech community, and entrenched as language knowledge in the learner’s mind. They are the symbolic units of language relating the defining properties of their morphological, lexical, and syntactic form with particular semantic, pragmatic, and discourse functions (Goldberg, 2006). Verbs are central in this: their semantic behavior is strongly intertwined with the syntagmatic constraints. Construction Grammar argues that all grammatical phenomena can be understood as learned pairings of form (from morphemes, words, idioms, to partially lexically filled and fully general