Human languages are not static entities. Linguistic conventions, whose social and communicative meaning are understood by all members of a speech community, are gradually altered or replaced, whether by changing their forms, meanings, or by the loss of or introduction of altogether new distinctions. How do large speech communities go about re-negotiating arbitrary associations in the absence of centralised coordination? This thesis first provides an overview of the plethora of explanations that have been given for language change. Approaching language change in a quantitative and evolutionary framework, mathematical and computational modelling is put forward as a tool to investigate and compare these different accounts and their purported underlying mechanisms in a rigorous fashion. The central part of the thesis investigates a relatively recent addition to the pool of mechanisms that have been proposed to influence language change: I will compare previous accounts with a momentum-based selection account of language change, a replicator-neutral model where the popularity of a variant is modulated by its momentum, i.e. its change in frequency of use in the recent past. I will discuss results from a multi-agent model which show that the dynamics of a trend-amplifying mechanism like this are characteristic of language change, in particular by exhibiting spontaneously generated s-shaped transitions. I will also discuss several empirical predictions made by a momentum-based selection account which contrast with those that can be derived from other accounts of language change. Going beyond theoretical arguments for the role of trends in language change, I will go on to present fieldwork data of speakers’ awareness of ongoing syntactic changes in the Shetland dialect of Scots. Data collected using a novel questionnaire methodology show that individuals possess explicit knowledge about the direction as well as current progression of ongoing changes, even for grammatical structures which are very low in frequency. These results complement previous experimental evidence which showed that individuals both possess and make use of implicit knowledge about age-dependent usage differences during ongoing sound changes. Echoing the literature on evolutionary approaches to language change, the final part of the thesis stresses the importance of explicitly situating different pressures either in the domain of the innovation of new or else the selection of existing variants. Based on a modification of the Wright-Fisher model from population genetics, I will argue that trend-amplification selection mechanisms provide predictions that neatly match empirical facts, both in terms of the diachronic dynamics of language change, as well as in terms of the synchronic distribution of linguistic traits that we find in the world.

This thesis examines the historical development of the expletive það in Icelandic, from the earliest texts to the present day. This development is set against the backdrop of Icelandic clause structure, with particular attention to verb-second, information structure and the left periphery. The study combines corpus linguistic data and quantitative techniques with theoretical analysis, conducted within Lexical Functional Grammar. I show that Icelandic underwent three syntactic developments in the period 1750-present and argue that these all reflect one overall change: the establishment of það as a structural placeholder for the topic position (the clause-initial prefinite position). I claim that það functions as a topic position placeholder in the earliest attested stage of Icelandic (1150-1350), but is restricted to a specific context: topicless subjectless constructions with a clausal object, where það has cataphoric reference. The three changes in the period 1750-present represent the establishment of this topic position placeholder in new contexts: (1) það generalises to all types of topicless subjectless construction, beyond those with a clausal object; (2) það emerges in presentational constructions (which inherently lack a topic), out-competing the earlier expletive form þar; (3) in cataphoric contexts with a clausal subject, það begins to transition from subject to topic position placeholder. The majority of these contexts exhibit at least a short period in which það - or alternatively þar - behaves like a subject. Icelandic thus exhibits the emergence of a topic position placeholder expletive from an earlier subject-like element. This shift towards prefinite expletives, which sets Icelandic apart from e.g. Mainland Scandinavian, happens relatively late in the diachrony (1750-present). Moreover, the Icelandic development challenges the standard claim in the literature on Germanic expletives, which assumes that subject expletives emerge from prefinite expletives.

L'objectiu general de la tesi és analitzar els objectius i les hipòtesis de què Pompeu Fabra (1891-1948) va partir en la codificació de la sintaxi del català i la metodologia que va fer servir. Per fer-ho s'ha identificat, buidat i analitzat la terminologia de 995 textos de Fabra, classificats segons la seva importància. Com a resultat s'ha obtingut una descripció de les concepcions fabrianes de sintaxi i proposició, de canvi sintàctic, de variació sintàctica, de codificació sintàctica i de la relació que Fabra hi estableix. Els resultats d'aquesta descripció s'han contrastat amb els d'estudis anteriors de l'obra fabriana. Finalment, s'han establert les perspectives que aquest resultats obren a nous estudis sobre les fonts de l'obra de Fabra, les seves coincidències amb altres teòrics del món i la seva influència en obres catalanes posteriors. / The general purpose oh the thesis is to analyse the purposes and hypothesis assumed by Pompeu Fabra (1891-1948), and his methodology when codifying catalan syntax. To do that, the terminology of 995 fabrian texts (which have been classified according to its importance) has been identified, extracted, and classified. The result of these operations is that a description of Fabra's conceptions about syntax and sentence, syntactic change, syntactic variation, and syntactic codification, and of the relationship established by him between these conceptions, has been established. The results of this description have been compared with the results of previous studies on Fabra's works. Finally, we have established the fields of study that these results allow to undertake, on the sources of Fabra's work, the coincidencies of it with other scholars' works in the world and its influence on later catalan studies.

The subject of the present thesis is an analysis of the ditransitive verbs envy and forgive in the ditransitive/double-object constructions, i.e., either the S-V-Oi-Od or S-V-O-Oprep argument structure, in which both objects are explicitly expressed. Envy and forgive represents marginal ditransitive verbs, whose accounts in major grammars and various studies are far from uniform. Occasionally considered idiosyncratic, the ditransitive use (i.e., the indirect pattern) of the two verbs is expected to decrease in frequency. Thus, the research aims to investigate the postverbal complementation preference of envy and forgive, and the way the preference changes over time. However, it is not the relative frequency of the S-V-Oi-Od pattern with respect to all remaining constructions that is of interest here, but its ratio to the frequency of the other available double object construction, the prepositional S-V-O-Oprep pattern. Additionally, the thesis provides a systematic overview of syntactic and semantic differences between envy and forgive as well as an account of their shared features and aspects. Particular attention is paid to the Oi/O realisation (e.g., the substantival or pronominal realisation) and the Od/Oprep realisation (namely, the substantival realisation, the pronominal realisation, the...