September 4, 2001
Marino: Dolphins check their look in the mirror, too
By Michael Terrazas email@example.com
Its long been suspected that dolphins are the smartest creatures
in the sea. But a recent study by Lori Marino suggests the marine mammals
are even more intelligent than previously known and possess cognitive
abilities thought to exist only in humans and great apes.
Marino, a lecturer in neuroscience and behavioral biology, conducted
a three-year study with Diana Reiss, a senior research scientist at the
New York Aquarium in Brooklyn, that shows dolphins have the capacity for
mirror self-recognition (MSR), a feat of intelligence heretofore thought
to be reserved only for Homo sapiens and their closest cousins. The findings
were published this past spring in the Proceedings of the National
Academy of Sciences.
Marino and Reiss used what is known as a mark test to measure
the trait; with bottlenose dolphins as their subjects, the researchers
marked the animals with a dye in a location not normally visible (for
example, the side of the dolphins head). In every case, as soon
as the animal was marked, it raced to an underwater mirror to check out
The finding holds implications not just for marine biologists or dolphin
enthusiasts, but for people like Marino who study cognitive processes
and neuroanatomy. Dolphin brains lack a frontal lobe, the region of the
brain thought to be responsible for many higher cognitive functions in
primates. This finding suggests that, while the frontal lobe certainly
plays a major role in primate intelligence, it is not the basis for intelligence
This is really a striking case of convergent evolution, said
Marino, using a term that means the same trait evolving independently
in different species. Its interesting that two very different
lineages of mammal show the same, very rare capacity. The brains of primates
and of dolphins are so differentthey havent shared a common
ancestor for at least 90 million years.
It also means Marinos conclusion is finding some resistance among
scientists who have a stake in certain theories of cognition that would
require revision if dolphin MSR is true. But Marino, a research associate
in the Living Links Center at Yerkes, brushed off such professional cynicism
with the hope that other researchers replicate her findings.
Most of my colleagues, especially those who have worked with dolphins,
are not surprised by the finding because theyve had experience with
the intelligence of this animal, Marino said. Dolphins, chimpanzees
and great apes show the same sort of affinity for [certain cognitive]
tasks, so I think the proof is in the pudding.
She also said that working with colleagues like Frans de Waal, one of
the worlds leading primatologists, has helped her immensely. My
association with Living Links has been invaluable, she said. Frans
is a broad-minded scientist and has some very interesting ideas about
what the distribution of higher-level cognitive capacities might be in
the animal kingdom.
Marino has been working with dolphins since graduate school, and though
she said it can be inconvenient working with an animal not readily availablethe
closest live dolphins (not swimming free in the ocean) are likely those
at Sea World in Orlando, Fla.she has not had many problems finding
Most of my research on dolphins is on their brain, and I get those postmortem from stranded animals, Marino said. But Ive been able to get access to [live dolphins] and conduct tests. Things are more possible than you would imagineif youre persistent.