International Journal of Comparative Psychology

The ability to recognize oneself in the mirror is assumed to represent an important step towards a higher level of animal intelligence that, ultimately, can lead to human-like self-awareness and empathy. Even though rarely successful in the classical mark test, the siamang’s spontaneous behavior in front of the mirror, a visually controlled manipulation of its face, suggests that it interprets the reflection as belonging to itself. As a consequence, the cognitive status of the gibbons may need a serious reevaluation since, in total, at least three species ( Hylobates syndactylus , H.gabriellae , H. leucogenys ) seem to be capable of self-recognition. Their, nonetheless, weak interest in the mirror image is hypothesized to be caused by the comparatively low level of sexual competition in the lesser apes.