Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence

Abstract

The ability to recognize oneself in a mirror is an exceedingly rare capacity in the animal kingdom. To date, only humans and great apes have shown convincing evidence of mirror self-recognition. Two dolphins were exposed to reflective surfaces, and both demonstrated responses consistent with the use of the mirror to investigate marked parts of the body. This ability to use a mirror to inspect parts of the body is a striking example of evolutionary convergence with great apes and humans.T he capacity for mirror self-recognition (MSR) has been found only in humans and great apes (1-8). In humans, MSR does not emerge reliably until 18-24 months of age (9) and marks the beginning of a developmental process of achieving increasingly abstract psychological levels of self-awareness, including introspection and mental state attribution (10, 11). The first evidence for MSR in a nonhuman species was experimentally demonstrated in the common chimpanzee (1), but numerous subsequent attempts showed no convincing evidence of self-recognition in a variety of other primates and nonprimates, including monkeys, lesser apes, and elephants (12-18). All of these species, including African gray parrots (19) demonstrate the ability to use a mirror to mediate or guide their behavior. A provocative debate continues to rage about whether self-recognition in great apes implies that they are also capable of more abstract levels of self-awareness (20). Therefore, research on self-recognition in other species will have profound implications for the idea that humans are the only species to conceive of their own identity.The apparent confinement of self-recognition to great apes and humans has stimulated scientific interest in the evolutionary significance of MSR based on common aspects of the social ecology, cognition, and neurobiology of these species (21-25). Dolphins have a high level of encephalization and behavioral and cognitive complexity (26-29), but previous attempts to demonstrate MSR in dolphins have been suggestive yet inconclusive because of difficulties in implementing adequate controls necessary to obtain robust evidence of MSR in an animal unable to display self-recognition by touching a marked part of the body with a hand (30,31).Conclusive evidence of self-recognition in a species as phylogenetically distant from primates as dolphins would play a pivotal role in determining whether this capacity is a byproduct of factors specific to great apes and humans or whether more general characteristics, such as a high level of encephalization, could help to explain the evolution of this capacity. General Methods and ProceduresThis study relies on sampling sufficient combinations of control and test situations to produce specificity effectively equivalent to hand use. We conducted a two-phase experiment to independently test whether two dolphins would use a mirror to view themselves after being marked, sham-marked, or not marked (untouched) in the presence or absence of reflective surfaces. During Phase 1, one subject was marked and s...

Von Economo Neurons in the Elephant Brain

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Neuroanatomy of the common dolphin (Delphinus delphis) as revealed by magnetic resonance imaging (MRI)

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Self-recognition, theory-of-mind, and self-awareness: What side are you on?

“…Only human primates, chimpanzees, orangutans, and some bonobos, elephants, and dolphins have been shown to exhibit spontaneous mirror-guided selfexploration-e.g., self-directed behaviors such as examining body parts only visible in the mirror (for reviews, see Bard, Todd, Bernier, Love & Leavens, 2006;Gallup et al, 2002; also see Plotnik, de Waal & Reiss, 2006;Reiss & Marino, 2001). The aforementioned primates also pass the more formal "mark test" and will touch a red dot that has been inconspicuously applied to their brow or forehead.…”