Pragmatics concerns the material function of language use in the world, and thus touches on profound questions about the relationship between our cognition and the environments in which we operate. Both psycholinguistics and evolutionary linguistics have afforded greater attention to pragmatics in recent years. Though the potential of evolutionary psycholinguistics has been noted for over twenty-five years (e.g. Tooby & Cosmides, 1990; Scott-Phillips, 2010a), there has arguably been little dialogue between these two fields of study. This thesis explicitly acknowledges and investigates the adaptationist nature of functional claims in psycholinguistics, and attempts to demonstrate that psycholinguistic inquiry can provide evidence that is relevant to theories of how the cognitive architecture of linguistic communication evolved. Chapter two reviews a broad polarisation in the pragmatic and psycholinguistic literature concerning the relative roles of linguistic convention and contextual information in comprehension. It makes explicit the theoretical approaches that reliably give rise to these polar positions across scholarly domains. It goes on to map each model of comprehension to the adaptationist particulars it may entail, and in doing so illustrates two different pictures of how linguistic cognition has developed over phylogeny. The Social Adaptation Hypothesis (SAH) holds that linguistic comprehension is performed by relevance-oriented inferential mechanisms that have been selected for by a social environment (i.e. inference-using conspecifics). In particular, the SAH holds that linguistic conventions are attended to in the same way as other ostensive stimuli and contextual information, and because of their relevance to communicative interactions. The Linguistic Adaptation Hypothesis (LAH) holds that linguistic comprehension is performed by specialised cognition that has been selected for by a linguistic environment (i.e. language-using conspecifics) that was established subsequent to, and as a consequence of, the emergence of inferential communication. In particular, the LAH holds that linguistic conventions are a privileged domain of input for the comprehension system. The plausibility and congruence of both accounts with the current state of knowledge about the evolutionary picture necessitates empirical psycholinguistic evidence. The remainder of the thesis presents a series of experiments investigating referential expressions relevant to the contrastive predictions of these two adaptationist accounts. The broad question that covers all of these experiments is: how sensitive is the comprehension process to linguistic input qua linguistic input, relative to various other grades of relevant contextual information? Chapter three presents a reaction time experiment that uses speaker-specific facts about referents as referring expressions, in a conversational precedent paradigm. The experiment measures the relative sensitivity of comprehension processing to the knowledge states of speakers and the consistent use of linguistic labels, and finds greater sensitivity to linguistic labels. Chapter four introduces a further contextual variable into this paradigm, in the form of culturally copresent associations between labels and referents. The experiment presented in this chapter compares the relative sensitivity of processing to culturally copresent common ground, the privileged knowledge state of speakers, and the consistent use of linguistic labels. The results indicated greater sensitivity to linguistic labels overall, and were consistent with the LAH. Chapter five turns to visual context as a constraint on reference, and presents two pairs of experiments. Experiments 3 and 4 investigate the comprehension of referring expressions across congruous, incongruous, and abstract visual contexts. The experiments measured reaction time as subjects were prompted to identify constituent parts of tangram pictures. The results indicated a sensitivity to the visual context and the linguistic labels, and are broadly consistent with the SAH. If comprehension is characterised by particular sensitivities, we may expect speakers to produce utterances that lend themselves well to how hearers process them. Experiments 5 and 6 use a similar tangram paradigm to elicit referring expressions from speakers for component parts of tangrams. The experiments measure the consistency of produced labels for the same referents across visual contexts of varied congruity. The results indicated some methodological limitations of the tangram paradigm for the study of repeated reference across contexts. Lastly, the thesis concludes by considering the SAH and LAH in light of the empirical evidence presented and its accompanying limitations, and argues that the evidence is generally consistent with the assumptions of the LAH.

Languages and species both evolve by a process of repeated divergences, which can be described with the branching of a phylogenetic tree or phylogeny. Taking advantage of this fact, it is possible to study language change using computational tree building techniques developed for evolutionary biology. Mathematical approaches to the construction of phylogenies fall into two major categories: character based and distance based methods. Character based methods were used in prior work in the application of phylogenetic methods to the Indo-European family of languages by researchers at the University of Pennsylvania. Discussion of the limitations of character-based models leads to a similar presentation of distance based models. We present an adaptation of these methods to linguistic data, and the phylogenies generated by applying these methods to several modern Germanic languages and Spanish. We conclude that distance based for phylogenies are useful for historical linguistic reconstruction, and that it would be useful to extend existing tree drawing methods to better model the evolutionary effects of language contact.

Previous research in evolutionary linguistics has made wide use of artificial language learning (ALL) paradigms, where learners are taught artificial languages in laboratory experiments and are subsequently tested in some way about the language they have learnt. The ALL framework has proved particularly useful in the study of the evolution of language, allowing the manipulation of specific linguistic phenomena that cannot be isolated for study in natural languages. Furthermore, this framework can test the output of individual participants, to uncover the cognitive biases of individual learners, but can also be implemented in a cultural evolutionary framework, investigating how participants acquire and change artificial languages in populations where they learn from and interact with each other. In this thesis, I present a novel methodology for studying the evolution of language in experimental populations. In the artificial sign language learning (ASLL) methodology I develop throughout this thesis, participants learn manual signalling systems that are used to interact with other participants. The ASLL methodology combines features of previous ALL methods as well as silent gesture, where hearing participants must communicate using only gesture and no speech. However, ASLL provides several advantages over previous methods. Firstly, reliance on the manual modality reduces the interference of participants’ native languages, exploiting a modality with linguistic potential that is not normally used linguistically by hearing language users. Secondly, research in the manual modality offers comparability with the only current evidence of language emergence and evolution in natural languages: emerging sign languages that have evolved over the last century. Although the silent gesture paradigm also makes use of the manual modality, it has thus far seen little implementation into a cultural evolutionary framework that allows closer modelling of natural languages that are subject to the processes of transmission to new learners and interaction between language users. The implementation and development of ASLL in the present work provides an experimental window onto the cultural evolution of language in the manual modality. I detail a set of experiments that manipulate both linguistic features (investigating category structure and verb constructions) and cultural context, to understand precisely how the processes of interaction and transmission shape language structure. The findings from these experiments offer a more precise understanding of the roles that different cultural mechanisms play in the evolution of language, and further builds a bridge between data collected from natural languages in the early stages of their evolution and the more constrained environments of experimental linguistic research.

Investigamos, nesta tese, as bases filogenéticas do léxico humano e o modo como elas foram articuladas às habilidades combinatoriais no curso da evolução. Partimos de uma avaliação da interação entre o léxico e a sintaxe com o intuito de determinar quanto da derivação sintática é dependente de informações lexicais e, em que medida, as propostas disponíveis são coerentes com o desenvolvimento evolutivo humano. Nosso objetivo principal é fornecer uma hipótese para a interface entre o léxico e a sintaxe que seja explicativa e evolutivamente adequada. Para esclarecer as discordâncias empíricas e teóricas observadas, propomos, em contrapartida, uma nova abordagem para a gramática, a Abordagem Isomórfica. Argumentamos que o léxico humano decorre do agrupamento de um conjunto de sistemas pré-adaptados que evoluíram separadamente um sistema conceitual-intencional, um sistema sensório-motor e um sistema funcional, cuja integração é um produto direto da emergência de um sistema combinatorial recursivo. Operacionalmente, buscamos, com essa abordagem, reduzir a influência lexical na formação de um objeto linguístico, na tentativa de assegurar uma isonomia funcional entre o léxico e a sintaxe. Motivamos, adicionalmente, a exaptação de um sistema responsável por derivar as unidades discretas empregadas pelo sistema combinatorial, a que damos o nome de sistema funcional. Compartilhado com primatas não humanos, o sistema funcional justifica-se pelo paralelismo entre a denotação rígida das vocalizações de alerta de primatas não humanos e o conteúdo fixo das unidades funcionais da linguagem humana. Propomos, com base nessa correlação, que os mecanismos cognitivos subjacentes aos sistemas de vocalização primata, instanciados pelo sistema funcional, correspondem aos precursores filogenéticos dos traços formais. Funcionalmente, essa nova abordagem incorpora a visão neoconstrucionista de que a derivação da estrutura sintática independe de informações codificadas nas entradas lexicais. Tal conjectura assegura a autonomia funcional da sintaxe, o que, como resultado, nos aproxima do caminho para se ir além da adequação explicativa. / We investigate, in this dissertation, the phylogenetic bases of human lexicon and how they were articulated with combinatorial abilities in evolution. We begin with an evaluation of the interaction between lexicon and syntax to determine how much of the syntactic derivation is dependent on lexical information, and to which extent the available proposals are consistent with human evolutionary development. Our main goal is to come up with an account for the lexicon-syntax interface that is both explanatory and evolutionarily adequate. In an attempt to eliminate the observed empirical and theoretical divergences, we propose a new approach to grammar, the Isomorphic Approach. We claim the human lexicon arouse from the assemblage of a set of pre-adapted systems that evolved separately viz., a conceptual-intentional, a sensory-motor, and a functional system, whose integration is a by-product of the emergence of a recursive combinatorial system. Operationally, we seek, with this approach, to reduce the burden of lexical influence in the derivation of a linguistic object, with the view to establish a functional isonomy between lexicon and syntax. Furthermore, we motivate the exaptation of a pre-adapted system responsible for deriving the discrete units that feed the combinatorial engine, which we call functional system. Shared with non-human primates, the functional system finds justification in the parallel between the rigid denotation of non-human primate alert calls and the fixed content of human language functional units. We propose, based on this conjecture, that the cognitive mechanisms underlying non-human primate alarm-calling systems, suggestively made available by the functional system, comprise the phylogenetic precursors of human language formal features. Functionally, this new approach incorporates the neo-constructionist view that the derivation of a syntactic structure is independent of lexically encoded instructions. With this premise, we aim to ensure the establishment of an autonomous syntax, which, as a result, brings us closer to the road toward a level of explanation that goes beyond explanatory adequacy.

Investigamos, nesta tese, as bases filogenéticas do léxico humano e o modo como elas foram articuladas às habilidades combinatoriais no curso da evolução. Partimos de uma avaliação da interação entre o léxico e a sintaxe com o intuito de determinar quanto da derivação sintática é dependente de informações lexicais e, em que medida, as propostas disponíveis são coerentes com o desenvolvimento evolutivo humano. Nosso objetivo principal é fornecer uma hipótese para a interface entre o léxico e a sintaxe que seja explicativa e evolutivamente adequada. Para esclarecer as discordâncias empíricas e teóricas observadas, propomos, em contrapartida, uma nova abordagem para a gramática, a Abordagem Isomórfica. Argumentamos que o léxico humano decorre do agrupamento de um conjunto de sistemas pré-adaptados que evoluíram separadamente um sistema conceitual-intencional, um sistema sensório-motor e um sistema funcional, cuja integração é um produto direto da emergência de um sistema combinatorial recursivo. Operacionalmente, buscamos, com essa abordagem, reduzir a influência lexical na formação de um objeto linguístico, na tentativa de assegurar uma isonomia funcional entre o léxico e a sintaxe. Motivamos, adicionalmente, a exaptação de um sistema responsável por derivar as unidades discretas empregadas pelo sistema combinatorial, a que damos o nome de sistema funcional. Compartilhado com primatas não humanos, o sistema funcional justifica-se pelo paralelismo entre a denotação rígida das vocalizações de alerta de primatas não humanos e o conteúdo fixo das unidades funcionais da linguagem humana. Propomos, com base nessa correlação, que os mecanismos cognitivos subjacentes aos sistemas de vocalização primata, instanciados pelo sistema funcional, correspondem aos precursores filogenéticos dos traços formais. Funcionalmente, essa nova abordagem incorpora a visão neoconstrucionista de que a derivação da estrutura sintática independe de informações codificadas nas entradas lexicais. Tal conjectura assegura a autonomia funcional da sintaxe, o que, como resultado, nos aproxima do caminho para se ir além da adequação explicativa. / We investigate, in this dissertation, the phylogenetic bases of human lexicon and how they were articulated with combinatorial abilities in evolution. We begin with an evaluation of the interaction between lexicon and syntax to determine how much of the syntactic derivation is dependent on lexical information, and to which extent the available proposals are consistent with human evolutionary development. Our main goal is to come up with an account for the lexicon-syntax interface that is both explanatory and evolutionarily adequate. In an attempt to eliminate the observed empirical and theoretical divergences, we propose a new approach to grammar, the Isomorphic Approach. We claim the human lexicon arouse from the assemblage of a set of pre-adapted systems that evolved separately viz., a conceptual-intentional, a sensory-motor, and a functional system, whose integration is a by-product of the emergence of a recursive combinatorial system. Operationally, we seek, with this approach, to reduce the burden of lexical influence in the derivation of a linguistic object, with the view to establish a functional isonomy between lexicon and syntax. Furthermore, we motivate the exaptation of a pre-adapted system responsible for deriving the discrete units that feed the combinatorial engine, which we call functional system. Shared with non-human primates, the functional system finds justification in the parallel between the rigid denotation of non-human primate alert calls and the fixed content of human language functional units. We propose, based on this conjecture, that the cognitive mechanisms underlying non-human primate alarm-calling systems, suggestively made available by the functional system, comprise the phylogenetic precursors of human language formal features. Functionally, this new approach incorporates the neo-constructionist view that the derivation of a syntactic structure is independent of lexically encoded instructions. With this premise, we aim to ensure the establishment of an autonomous syntax, which, as a result, brings us closer to the road toward a level of explanation that goes beyond explanatory adequacy.

Si la question de l'origine du langage reste d'un abord compliqué, celle de l'origine des formes du langage semble plus susceptible de se confronter à la démarche expérimentale. Malgré leur infinie variété, d'évidentes régularités y sont présentes~: les universaux du langage. Nous les étudions par des raisonnements plus généraux sur l'émergence du langage, notamment sur la recherche de précurseurs onto- et phylogénétiques. Nous abordons trois thèmes principaux~: la situation de communication parlée, les architectures cognitives des agents et l'émergence des universaux du langage dans des sociétés d'agents. Notre première contribution est un modèle conceptuel des agents communicants en interaction, issu de notre analyse bibliographique. Nous en proposons ensuite une formalisation mathématique Bayésienne~: le modèle d'un agent est une distribution de probabilités, et la production et la perception sont des inférences bayésiennes. Cela permet la comparaison formelle des différents courants théoriques en perception et en production de la parole. Enfin, nos simulations informatiques de société d'agents identifient les conditions qui favorisent l'apparition des universaux du langage. / If the origin of language is difficult to properly study, the origin of its forms appears to be accessible to the experimental method. Languages, despite their large variety, display obvious regularities, the linguistic universals. We study them through more general reasoning about language emergence, in particular in the search of its precursors, both in ontogeny and phylogeny. We study three main themes: the communication situation, the agent's cognitive architectures and the emergence of linguistic universals in agent societies. Our first contribution is a conceptual model of communicating agents in interaction, emanating from our bibliographic survey. We then cast it into the Bayesian mathematical formalism: an agent model is a probability distribution, and production and perception are defined by Bayesian inference. This allows a formal comparison of speech perception and production theoretical trends. Finally, computer simulations of agent societies help identify the conditions that favor the appearance of linguistic universals.

Language is arguably one of the most salient features that distinguish humans from other animal species. However, despite the existence of a large body of relevant theoretical and empirical research, there is currently no consensus as to why language emerged exclusively in the human species or how it evolved its unique communicative structure. In this thesis, I therefore take a multi-pronged approach to analysing and testing several different hypotheses for the biological function and evolution of language. In Chapter I, I review the evidence and theoretical arguments for each of these proposals and provide, in place, a synthetic perspective which integrates or eliminates each of these ostensibly competing hypotheses for the biological function of language. In Chapter II, I employ the first experimental test of the interdependence hypothesis: the unique proposal offered to explain the emergence and potential coevolution of language and cooperation in the human species. In pursuit of this experiment, I employed a cooperative social foraging task using small and large groups to determine what factors enable individuals to make sense of information from others and converge upon a group consensus. In Chapter III, I take an experimental approach to determine whether aspects of human language can be characterised in terms of honest signalling theory. In this respect, I test several different proposals predicted by the sexual selection and deception hypotheses for human language function. In Chapter IV, I divert attention away from biological function to focus more closely on language structure. More specifically, I take an experimental approach to the problem of how and indeed whether recursive syntax evolved to be a consistent feature of human language. In pursuit of this experiment, I utilized the Imposing Memory Task (IMT) and a recursive syntax measure, to determine relative performance on each of these cognitive tasks, thereby testing whether recursive syntax may have evolved in tandem with higher-order intentionality (also known as embedded mindreading). Finally, in Chapter V, I discuss the results and implications of these experiments, and possible suggestions for future studies.