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Dolphins Recognize Themselves in the Mirror Before Babies Do

Babies show signs of recognizing themselves in the mirror at about 15 to 18 months of age. But dolphins can recognize themselves even earlier—as young as 7 months old, according to a study recently published in PLOS One.

Self-recognition takes sophisticated cognitive processing and was once thought to be a uniquely human ability. But since the 1970s, great apes, elephants, dolphins, and magpies (yes, a crow) have shown the capacity to recognize themselves in a mirror.

Highly precocious animals, dolphins develop much faster than humans. At just 1 week old, they display social play behaviors with other dolphins and have to synchronize their swimming and breathing with others. Given this early social development, Hunter College Professor Diana Reiss, a co-author of the study, wanted to see if dolphins had the ability to self-recognize at an early age, as these behaviors often go hand in hand.

The authors placed a one-way mirror in a dolphin tank at the National Aquarium in Baltimore and watched two young bottlenose dolphins as they interacted with their own mirror image over the course of three years. Even at 5 months, one dolphin started showing signs of recognition, such as twirling, close-eye viewing, blowing bubbles, and doing barrel roles. By 7 months, this behavior was well established. “We knew it would be early, but we didn’t know it would be that early,” says Reiss. The other dolphin was introduced to the mirror at 14 months and immediately displayed self-recognition behavior.

Self-recognition has been associated with the development of social awareness and the ability to monitor one’s own behavior. Animals that self-recognize have a few similar traits, including a large and complex brain, social awareness, and the ability to empathize. They also seem to like to preen in front of the mirror: The dolphins used the mirrors to look into their mouths, look at parts of their body they can’t see without a mirror, and watch their own movements. The study was also featured in The New York Times.

Beyond SUM

Explore This Work
Precocious development of self-awareness in dolphins
PLOS One, 2018

Work By
Diana Reiss (Professor, Psychology) | Profile 1 | Profile 2

Colleges and Schools
Hunter College
The Graduate Center

Bonus Content
New Study Finds Dolphins Demonstrate Self-Awareness Earlier than Humans and Chimpanzees (Hunter News)

Dolphins Show Self-Recognition Earlier Than Children (The New York Times)

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