The last three decades of the 20th century have seen keen interest in the study of self-awareness in nonhuman primates. This area has been dominated by experiments using mirror-image stimulation. Typically, monkeys or apes are observed in the presence of their reflection and monitored for any signs that they correctly interpret the image as a representation of their own body. Self-recognition is admitted for a primate that spontaneously uses the image to check its visual appearance, more specifically to explore parts of its body that cannot be seen without the aid of a mirror. Confirmatory evidence may take the form of the individual using the reflection to visually and tactually explore a mark surreptitiously placed on an normally unseen body part (usually the head) which is ignored in the absence of the mirror (for reviews see Anderson 1984a; Gallup 1994; Parker et al. 1994).