1. Early Cognitive Development Centre, School of Psychology, University of Queensland, Queensland, Australia
2. School of Psychology, University of Birmingham, Edgbaston, Birmingham, West Midlands B15 2TT, UK
3. School of Psychology and Neuroscience, University of St Andrews, St Mary's Quad, St Andrews KY16 9JP, UK
4. Department of Early Prehistory and Quaternary Ecology, University of Tübingen, Tubingen, Germany
5. Department of Communication, University of Johannesburg, Auckland Park, South Africa