Contact-tracing in cultural evolution: a Bayesian mixture model to detect geographic areas of language contact

Journal of The Royal Society Interface, vol. 18, pp. 20201031

Abstract

When speakers of different languages interact, they are likely to influence each other: contact leaves traces in the linguistic record, which in turn can reveal geographical areas of past human interaction and migration. However, other factors may contribute to similarities between languages. Inheritance from a shared ancestral language and universal preference for a linguistic property may both overshadow contact signals. How can we find geographical contact areas in language data, while accounting for the confounding effects of inheritance and universal preference? We present sBayes, an algorithm for Bayesian clustering in the presence of confounding effects. The algorithm learns which similarities are better explained by confounders, and which are due to contact effects. Contact areas are free to take any shape or size, but an explicit geographical prior ensures their spatial coherence. We test sBayes on simulated data and apply it in two case studies to reveal language contact in South America and the Balkans. Our results are supported by findings from previous studies. While we focus on detecting language contact, the method can also be used to uncover other traces of shared history in cultural evolution, and more generally, to reveal latent spatial clusters in the presence of confounders.

Authors 8

1. Peter Ranacher corresponding

   University of Zurich

   Affiliation as printed

   Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zurich, Switzerland

   Department of Geography, University of Zurich, Zurich, Switzerland

   University Research Priority Program (URPP) Language and Space, University of Zurich, Zurich, Switzerland

2. Nico Neureiter

   University of Zurich

   Affiliation as printed

   Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zurich, Switzerland

   Department of Geography, University of Zurich, Zurich, Switzerland

   University Research Priority Program (URPP) Language and Space, University of Zurich, Zurich, Switzerland

3. Rik van Gijn Aachen

   Leiden University

   Affiliation as printed

   Leiden University Centre for Linguistics, Leiden, Netherlands

4. Barbara Sonnenhauser

   University of Zurich

   Affiliation as printed

   Department of Slavonic Languages and Literatures, University of Zurich, Zurich, Switzerland

5. Anastasia Escher

   University of Zurich

   Affiliation as printed

   Department of Slavonic Languages and Literatures, University of Zurich, Zurich, Switzerland

6. Robert Weibel

   University of Zurich

   Affiliation as printed

   Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zurich, Switzerland

   Department of Geography, University of Zurich, Zurich, Switzerland

   University Research Priority Program (URPP) Language and Space, University of Zurich, Zurich, Switzerland

7. Pieter C. Muysken

   Radboud University Nijmegen · Center for Language Studies

   Affiliation as printed

   Centre for Language Studies, Radboud University Nijmegen, Nijmegen, Netherlands

8. Balthasar Bickel

   University of Zurich

   Affiliation as printed

   Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zurich, Switzerland

   Department of Comparative Language Science, University of Zurich, Zurich, Switzerland

   University Research Priority Program (URPP) Language and Space, University of Zurich, Zurich, Switzerland