Statistical Modeling of Creole Genesis

Proceedings of NAACL-HLT 2016, pages 1329–1339, San Diego, California, June 12-17, 2016. c⃝2016 Association for Computational Linguistics Statistical Modeling of Creole Genesis Yugo Murawaki Graduate School of Informatics, Kyoto University Yoshida-honmachi, Sakyo-ku, Kyoto, 606-8501, Japan murawaki@i.kyoto-u.ac.jp Abstract Creole languages do not fit into the tradi- tional tree model of evolutionary history be- cause multiple languages are involved in their formation. In this paper, we present several statistical models to explore the nature of cre- ole genesis. After reviewing quantitative stud- ies on creole genesis, we first tackle the ques- tion of whether creoles are typologically dis- tinct from non-creoles. By formalizing this question as a binary classification problem, we demonstrate that a linear classifier fails to sep- arate creoles from non-creoles although the two groups have substantially different distri- butions in the feature space. We then model a creole language as a mixture of source lan- guages plus a special restructurer. We find a pervasive influence of the restructurer in cre- ole genesis and some statistical universals in it, paving the way for more elaborate statisti- cal models. 1 Introduction While most linguistic applications of computational phylogeny rely on lexical data (Gray and Atkinson, 2003; Bouckaert et al., 2012), there is a growing trend to make use of typological data (Tsunoda et al., 1995; Dunn et al., 2005; Teh et al., 2008; Longo- bardi and Guardiano, 2009; Murawaki, 2015). One advantage of typological features over lexical traits (cognates) is that they allow us to compare an ar- bitrary pair of languages even if they do not share enough cognates. For this reason, they have the potential of uncovering external relations involving language isolates and tiny language families such as Ainu, Basque, and Japanese. However, our understanding of typological changes is far from satisfactory in at least two re- spects. First, typological changes are less intuitive than the birth and death of a lexical trait. Mod- eling word-order change with a single transition matrix (Maurits and Griffiths, 2014), for example, appears to be an oversimplification because some complex mechanisms must be hidden behind the changes (Murawaki, 2015). The second point, the main focus of this paper, is that it is not clear whether typological data fit into the traditional tree model for a group of languages, which has long been used as the default choice to summarize evolutionary history (Schleicher, 1853). To be precise, regardless of whether typological fea- tures are involved, linguists have viewed the tree model with suspicion. A central problem of the tree model is its assumption that after a branching event, two resultant languages evolve completely indepen- dently. However, linguists have noted that horizon- tal contact is a constitutive part of evolutionary his- tory. Various models for contact phenomena have been proposed to address this problem, including the wave theory (Schmidt, 1872) and the gravity model (Trudgill, 1974). As for linguistic typology, areal linguistics has worked on the diffusion of typo- logical features across languages within a geograph- ical area (Campbell, 2006). In this paper, we study …

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