[1] Univ Neuchatel, Inst Biol, Dept Comparat Cognit, Neuchatel, Switzerland
[2] Univ Zurich, Dept Comparat Language Sci, Zurich, Switzerland
[3] Univ Zurich, Ctr Interdisciplinary Study Language Evolut ISLE, Zurich, Switzerland
[4] Liverpool John Moores Univ, Res Ctr Evolutionary Anthropol & Palaeoecol, Liverpool, England
[5] Res Inst Farm Anim Biol FBN, Inst Behav Physiol, Dummerstorf, Germany