a1 School of Psychology, University of Queensland, Brisbane, Qld 4072, Australia. email@example.com http://www.psy.uq.edu.au/directory/index.html?id=39
The real reason for the apparent discontinuity between human and nonhuman minds is that all closely related hominids have become extinct. Nonetheless, I agree with Penn et al. that comparative psychology should aim to establish what cognitive traits humans share with other animals and what traits they do not share, because this could make profound contributions to genetics and neuroscience. There is, however, no consensus yet, and Penn et al.'s conclusion that it all comes down to one trait is premature.