Who researched:
Diana Reiss and Lori Marino
When researched:
Received for review on October 3, 2000
Accepted February 20, 2001
Published online before print on May 1, 2001
Where researched:
New York Aquarium in Brooklyn, New York
Research methods:
Two subjects were used: a 13-year-old captive-born male bottlenose dolphin and a 17-year-old captive-born male bottlenose dolphin
During an experiment the dolphin being tested was videotaped 30 minutes prior to feeding (served as a control session) and 30 minutes after feeding (for a total of 63 tapings). During feeding, the dolphin being tested was marked, sham-marked or not marked at all. If marked, the researcher used a temporary nontoxic black ink marker to create a circle, triangle or X-shaped mark. The dolphin being tested was then either exposed to a mirror, a covered mirror (reflective side was turned away from the pool) or no mirror.
Four observers (two experienced dolphin researchers and two highly trained assistants) reviewed the videotapes and marked the duration, location and time of occurrence of specific behaviors. Behaviors caught on the videotape (after feeding) were put into four different categories: self-directed, non-directed, ambiguous or social.
–self-directed–behaviors in which the animal positioned himself at the reflective surface and oriented himself so that the marked area was visible to the animal in the mirror.
–exploratory–self-directed behaviors that included repetitious head circling, close viewing of the eye, and close viewing of the genital region directed at the reflective surface.
–social behaviors–behaviors typically observed when these dolphins confront a familiar or unfamiliar dolphin (jaw-clapping, charging, or affiliative responses).
33 sessions were conducted for the 13-year-old dolphin:
8 pre-feeding control sessions, 8 post-feeding control sessions, 1 post-feeding control session with an additional mirror present, 3 early sham-mark sessions, 6 mark sessions, 4 mark session with an additional mirror, and 3 late sham-mark sessions.
40 sessions were conducted for the 17-year-old dolphin:
20 non-marked pre-feeding control sessions, 11 post-feeding marked sessions with the mirror present, 5 marked conditions with a covered mirror or no mirror, and 4 unmarked conditions with the mirror.
Not all of these sessions were reviewed/used.
What they learned:
Both dolphins provided definitive evidence that they used the mirror to investigate parts of their bodies that were marked. Therefore, this is the first study to show evidence of a non-primate species being capable of mirror self-recognition. This study has provided several possible insights into the bottlenose dolphin: an evolutionary convergence with great apes and humans, an ability to use a mirror to mediate or guide their behavior, and that this species is capable of abstract levels of self-awareness.