A critical review of methodology and interpretation of mirror self-recognition research in nonhuman primates.

In this paper we critically review conceptual and methodological issues of mirror self-exploration research. We conclude that: (1) mirror self-exploration provides evidence for mirror self-recognition; (2) inter- and intraspecies differences in terms of presence or absence of mirror self-recognition are not yet sufficiently clear, that is, whether its absence in species and individuals is methodological (false negative with respect to trait) or ontological (true negative with respect to trait) in nature; and (3) proposals of hypotheses to account phylogenetically for the existence of inter- and intraspecies differences in mirror self-recognition are premature. Before hypotheses such as these are advanced, the impact of rearing conditions on mirror self-recognition should be examined further. Copyright 1999 The Association for the Study of Animal Behaviour.