 Sufka et al. (2009) have proposed that animal models of neuropsychiatric disorders may also support the experimental investigation of animal emotions. Although depending on a more anecdotal, non-experimental approach, Smuts (2001) and Bekoff (2007) each defend the attribution of conscious emotions to animals from a scientist's perspective. Bekoff has made much of play behavior as an indicator of animal emotions, an idea that is also taken up by Cabanac et al. (2009). 