Through animal eyes: What behaviour tells us

To Charles Darwin, it was obvious that animals are sentient, so why should the idea not be now universally accepted? I review the difficulties and issues with animal sentience with a view to answering some of the critics. Sentience is 'the hard problem' and it is important we acknowledge the difficulties and do not claim too much for the evidence we have. Two sorts of evidence are examined: evidence from animal cognition and evidence from animal emotion, including the ways we now have of 'asking' animals what they want, behaviour, brain imaging and parallels with our own emotions. Despite the problems, the study of animal sentience is one of the most important areas of biology. Although conclusive evidence that animals are sentient may elude us, evidence of what they want and how they see the world is increasingly open to us and it is important that it is used. There is a danger that well-meaning people define animal welfare in terms of what they think animals want or what pleases them. But if we take animal sentience seriously, we must ensure that the animal voice is heard. (c) 2006 Elsevier B.V. All rights reserved.