1. Department of Psychology, University of Stirling, Stirling FK9 4LA, UK
2. School of Psychology, University of St Andrews, St Andrews KY16 9fU, UK
3. Veterinary Services, University of Oxford, Oxford OX1 3PT, UK
4. Harlan UK, Hillcrest, Dodgeford Lane, Belton, Leicestershire LE12 9TE, UK