[1] Max Planck Inst Psycholinguist, Comparat Cognit Anthropol Grp, NL-6525 XD Nijmegen, Netherlands
[2] Univ Carlos III Madrid, Dept Matemat, GISC, Leganes 28911, Spain
[3] Univ Zaragoza, Inst Biocomputac & Fis Sistemas Complejos BIFI, Zaragoza 50018, Spain