Full story, photos, comments:
shows that we have grossly underestimated both the scope and the scale of
animal intelligence. Primatologist Frans de Waal on memory-champ chimps,
tool-using elephants and rats capable of empathy
Who is smarter: a
person or an ape? Well, it depends on the task. Consider Ayumu, a young male
chimpanzee at Kyoto University who, in a 2007 study, put human memory to
shame. Trained on a touch screen, Ayumu could recall a random series of nine
numbers, from 1 to 9, and tap them in the right order, even though the
numbers had been displayed for just a fraction of a second and then replaced
with white squares.
I tried the task myself and could not keep track
of more than five numbers--and I was given much more time than the brainy
ape. In the study, Ayumu outperformed a group of university students by a
wide margin. The next year, he took on the British memory champion Ben
Pridmore and emerged the "chimpion."
How do you give a chimp--or an
elephant or an octopus or a horse--an IQ test? It may sound like the setup to
a joke, but it is actually one of the thorniest questions facing science
today. Over the past decade, researchers on animal cognition have come up
with some ingenious solutions to the testing problem. Their findings have
started to upend a view of humankind's unique place in the universe that
dates back at least to ancient Greece.
Aristotle's idea of the scala
naturae, the ladder of nature, put all life-forms in rank order, from low to
high, with humans closest to the angels. During the Enlightenment, the
French philosopher Rene Descartes, a founder of modern science, declared
that animals were soulless automatons. In the 20th century, the American
psychologist B.F. Skinner and his followers took up the same theme, painting
animals as little more than stimulus-response machines. Animals might be
capable of learning, they argued, but surely not of thinking and feeling.
The term"animal cognition" remained an oxymoron.
A growing body of
evidence shows, however, that we have grossly underestimated both the scope
and the scale of animal intelligence. Can an octopus use tools? Do
chimpanzees have a sense of fairness? Can birds guess what others know? Do
rats feel empathy for their friends? Just a few decades ago we would have
answered "no" to all such questions. Now we're not so sure.
Experiments with animals have long been handicapped by our anthropocentric
attitude: We often test them in ways that work fine with humans but not so
well with other species. Scientists are now finally meeting animals on their
own terms instead of treating them like furry (or feathery) humans, and this
shift is fundamentally reshaping our understanding.
Elephants are a
perfect example. For years, scientists believed them incapable of using
tools. At most, an elephant might pick up a stick to scratch its itchy
behind. In earlier studies, the pachyderms were offered a long stick while
food was placed outside their reach to see if they would use the stick to
retrieve it. This setup worked well with primates, but elephants left the
stick alone. From this, researchers concluded that the elephants didn't
understand the problem. It occurred to no one that perhaps we, the
investigators, didn't understand the elephants.
Think about the test
from the animal's perspective. Unlike the primate hand, the elephant's
grasping organ is also its nose. Elephants use their trunks not only to
reach food but also to sniff and touch it. With their unparalleled sense of
smell, the animals know exactly what they are going for. Vision is
But as soon as an elephant picks up a stick, its nasal
passages are blocked. Even when the stick is close to the food, it impedes
feeling and smelling. It is like sending a blindfolded child on an Easter
What sort of experiment, then, would do justice to the
animal's special anatomy and abilities?
On a recent visit to the
National Zoo in Washington, I met with Preston Foerder and Diana Reiss of
Hunter College, who showed me what Kandula, a young elephant bull, can do if
the problem is presented differently. The scientists hung fruit high up
above the enclosure, just out of Kandula's reach. The elephant was given
several sticks and a sturdy square box.
Kandula ignored the sticks
but, after a while, began kicking the box with his foot. He kicked it many
times in a straight line until it was right underneath the branch. He then
stood on the box with his front legs, which enabled him to reach the food
with his trunk. An elephant, it turns out, can use tools--if they are the
While Kandula munched his reward, the investigators
explained how they had varied the setup, making life more difficult for the
elephant. They had put the box in a different section of the yard, out of
view, so that when Kandula looked up at the tempting food he would need to
recall the solution and walk away from his goal to fetch the tool. Apart
from a few large-brained species, such as humans, apes and dolphins, not
many animals will do this, but Kandula did it without hesitation, fetching
the box from great distances.
Another failed experiment with
elephants involved the mirror test--a classic evaluation of whether an animal
recognizes its own reflection. In the early going, scientists placed a
mirror on the ground outside the elephant's cage, but the mirror was
(unsurprisingly) much smaller than the largest of land animals. All that the
elephant could possibly see was four legs behind two layers of bars (since
the mirror doubled them). When the animal received a mark on its body
visible only with the assistance of the mirror, it failed to notice or touch
the mark. The verdict was that the species lacked self-awareness.
Joshua Plotnik of the Think Elephant International Foundation modified the
test. He gave the elephants access to an 8-by-8-foot mirror and allowed them
to feel it, smell it and look behind it. With this larger mirror, they fared
much better. One Asian elephant recognized herself. Standing in front of the
mirror, she repeatedly rubbed a white cross on her forehead, an action that
she could only have performed by connecting her reflected image with her own
A similar experimental problem was behind the mistaken belief,
prevalent until two decades ago, that our species has a unique system of
facial recognition, since we are so much better at identifying faces than
any other primate. Other primates had been tested, but they had been tested
on human faces--based on the assumption that ours are the easiest to tell
When Lisa Parr, one of my co-workers at Emory University,
tested chimpanzees on portraits of their own species, they excelled at it.
Selecting portraits on a computer screen, they could even tell which
juveniles were born to which females. Having been trained to detect
similarities among images, the apes were shown a female's portrait and then
given a choice between two other faces, one of which showed her offspring.
They preferred the latter based purely on family resemblance since they did
not know any of the depicted apes.
We also may need to rethink the
physiology of intelligence. Take the octopus. In captivity, these animals
recognize their caretakers and learn to open pill bottles protected by
childproof caps--a task with which many humans struggle. Their brains are
indeed the largest among invertebrates, but the explanation for their
extraordinary skills may lie elsewhere. It seems that these animals think,
literally, outside the box of the brain.
Octopuses have hundreds of
suckers, each one equipped with its own ganglion with thousands of neurons.
These "mini-brains" are interconnected, making for a widely distributed
nervous system. That is why a severed octopus arm may crawl on its own and
even pick up food.
Similarly, when an octopus changes skin color in
self-defense, such as by mimicking a poisonous sea snake, the decision may
come not from central command but from the skin itself. A 2010 study found
gene sequences in the skin of cuttlefish similar to those in the eye's
retina. Could it be: an organism with a seeing skin and eight thinking arms?
A note of caution, however: At times we also have overestimated the
capacities of animals. About a century ago, a German horse named "Kluger
Hans" (Clever Hans) was thought to be capable of addition and subtraction.
His owner would ask him the product of multiplying four by three, and Hans
would happily tap his hoof 12 times. People were flabbergasted, and Hans
became an international sensation.
That is, until Oskar Pfungst, a
psychologist, investigated the horse's abilities. Pfungst found that Hans
was only successful if his owner knew the answer to the question and was
visible to the horse. Apparently, the owner subtly shifted his position or
straightened his back when Hans reached the correct number of taps. (The
owner did so unknowingly, so there was no fraud involved.)
Some look at
this historic revelation as a downgrading of Hans's intelligence, but I
would argue that the horse was in fact very smart. His abilities at
arithmetic may have been flawed, but his understanding of human body
language was remarkable. And isn't that the skill a horse needs most?
Awareness of the "Clever Hans Effect," as it is now known, has greatly
improved animal experimentation. Unfortunately, it is often ignored in
comparable research with humans. Whereas every dog lab now tests the
cognition of its animals while their human owners are blindfolded or asked
to face away, young children are still presented with cognitive tasks while
sitting on their mothers' laps. The assumption is that mothers are like
furniture, but every mother wants her child to succeed, and nothing
guarantees that her sighs, head turns and subtle changes in position don't
serve as cues for the child.
This is especially relevant when we try
to establish how smart apes are relative to children. To see how their
cognitive skills compare, scientists present both species with identical
problems, treating them exactly the same. At least this is the idea. But the
children are held by their parents and talked to ("Watch this!" "Where is
the bunny?"), and they are dealing with members of their own kind. The apes,
by contrast, sit behind bars, don't benefit from language or a nearby parent
who knows the answers, and are facing members of a different species. The
odds are massively stacked against the apes, but if they fail to perform
like the children, the invariable conclusion is that they lack the mental
capacities under investigation.
A recent study, tracking the pupil
movements of chimpanzees, found that they followed the gaze of members of
their own species far better than that of humans. This simple finding has
huge implications for tests in which chimpanzees need to pay attention to
human experimenters. The species barrier they face may fully explain the
difference in performance compared with children.
Underlying many of
our mistaken beliefs about animal intelligence is the problem of negative
evidence. If I walk through a forest in Georgia, where I live, and fail to
see or hear the pileated woodpecker, am I permitted to conclude that the
bird is absent? Of course not. We know how easily these splendid woodpeckers
hop around tree trunks to stay out of sight. All I can say is that I lack
It is quite puzzling, therefore, why the field of animal
cognition has such a long history of claims about the absence of capacities
based on just a few strolls through the forest. Such conclusions contradict
the famous dictum of experimental psychology according to which "absence of
evidence is not evidence of absence."
Take the question of whether we
are the only species to care about the well-being of others. It is well
known that apes in the wild offer spontaneous assistance to each other,
defending against leopards, say, or consoling distressed companions with
tender embraces. But for decades, these observations were ignored, and more
attention was paid to experiments according to which the apes were entirely
selfish. They had been tested with an apparatus to see if one chimpanzee was
willing to push food toward another. But perhaps the apes failed to
understand the apparatus. When we instead used a simple choice between
tokens they could exchange for food--one kind of token rewarded only the
chooser, the other kind rewarded both apes--lo and behold, they preferred
outcomes that rewarded both of them.
Such generosity, moreover, may
not be restricted to apes. In a recent study, rats freed a trapped companion
even when a container with chocolate had been put right next to it. Many
rats first liberated the other, after which both rodents happily shared the
The one historical constant in my field is that each time a
claim of human uniqueness bites the dust, other claims quickly take its
place. Meanwhile, science keeps chipping away at the wall that separates us
from the other animals. We have moved from viewing animals as
instinct-driven stimulus-response machines to seeing them as sophisticated
Aristotle's ladder of nature is not just being
flattened; it is being transformed into a bush with many branches. This is
no insult to human superiority. It is long-overdue recognition that
intelligent life is not something for us to seek in the outer reaches of
space but is abundant right here on earth, under our noses.
Waal is C.H. Candler Professor at Emory University and director of the
Living Links Center at the Yerkes National Primate Research Center, both in
Atlanta. His latest book, "The Bonobo and the Atheist: In Search of Humanism
among the Primates," will be published by Norton on Monday.