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Looking for Personality in Animals, of All People

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  • Teresa Binstock
    March 1, 2005 Looking for Personality in Animals, of All People By CARL ZIMMER
    Message 1 of 1 , Mar 1, 2005
      March 1, 2005

      Looking for Personality in Animals, of All People



      [chart of personality on url]

      Nature Stock Shots

      A team of Dutch scientists is trying to solve the mystery of
      personality. Why are some individuals shy while others are bold, for
      example? What roles do genes and environment play in shaping
      personalities? And most mysterious of all, how did they evolve?

      The scientists are carrying out an ambitious series of experiments to
      answer these questions. They are studying thousands of individuals,
      observing how they interact with others, comparing their personalities
      to their descendants' and analyzing their DNA.

      It may come as a surprise that their subjects have feathers. The
      scientists, based at the Netherlands Institute of Ecology, are
      investigating personalities of wild birds.

      Until recently, most experts in personality would have considered such a
      study as nothing but foolish anthropomorphism. "It's been looked at with
      suspicion and contempt," said Dr. Samuel Gosling, a psychologist at the
      University of Texas.

      But scientists have found that in many species, individual animals
      behave in consistently different ways. They argue that these differences
      meet the scientific definition of personality.

      If they are right, then human personality has deep evolutionary roots.
      "It's a matter of degree, not of differences," said Dr. Piet Drent of
      the Netherlands Institute of Ecology.

      The bird study that Dr. Drent and his colleagues are conducting is
      considered the most ambitious investigation of personality in wild animals.

      "They've gone the furthest," said Dr. Sasha Dall, an evolutionary
      biologist at the University of Exeter in Cornwall.

      The Dutch researchers are studying the importance of genes to the
      personalities of the birds, and the effect different personalities have
      on their survival. They hope next to carry out parallel studies in
      humans to see whether the same forces behind the evolution of bird
      personalities are at work in our own species.

      The science of human personality is about a century old. Psychologists
      have relied largely on questionnaires and other testing methods to map
      out its dimensions. One common method is for scientists to ask their
      subjects how well certain adjectives apply to themselves (or to people
      they know well).

      "Certain traits tend to go together," Dr. Gosling said. "We find that
      people who are energetic also tend to be talkative. It needn't be that
      way, but that's how it tends to be." The flip side is true as well: less
      energetic people tend to be less talkative.

      Psychologists have found they can bundle these traits into just a few
      personality dimensions. People may be more or less extroverted, for
      example, which means they are sociable, assertive and tend to have
      positive emotions. The same dimensions have been documented across the
      world, from Zimbabwe to the Russian Arctic, suggesting that they are
      universal in humans.

      Some studies have suggested that genes are responsible for some of the
      differences in people's personality ratings. But they have been far from
      conclusive because scientists cannot do experiments with humans. "Human
      mothers will not let you just swap their infants at birth, which would
      be a great study to do," Dr. Gosling said.

      It has been only in the last decade or so that scientists have
      investigated whether animals have personalities. In one pioneering study
      in the mid-1990's, Dr. Gosling studied a colony of 34 hyenas at the
      University of California, Berkeley. "My goal was simply to say, can we
      measure personality in animals? It wasn't clear it was going to work,"
      he said.

      Dr. Gosling asked the four caretakers of the colony to fill out a
      modified version of the human questionnaire for each animal.

      "It turned out that they agreed at the level you find in humans," Dr.
      Gosling said. What's more, the hyena personalities fit some of the
      dimensions found in humans, like neuroticism and agreeableness. Since
      then, a number of other studies have documented personalities in animals
      ranging from chimpanzees to squid.

      To some biologists, the main question about these animal personalities
      is why natural selection keeps such a wide range of them. "Why hasn't
      one personality become the standard in the population?" asked Dr. Drent.
      If being extroverted offers the best odds for a hyena to reproduce, you
      might expect that over time, all hyenas would wind up as extroverts.

      Dr. Drent and his colleagues hope that their study on birds may reveal
      some clues. They are studying a European relative of chickadees called
      the great tit (Parus major). Most of the birds spend their entire lives
      in a single forest, and they are happy to move into comfortable nest
      boxes provided by the scientists. As a result, the Dutch researchers can
      track the entire population of birds for years, keeping tabs on their
      health and their success at reproducing.

      The scientists can also bring some of the birds into the lab in order to
      measure their personalities or carry out breeding experiments.

      "These birds are perfect for these sorts of studies," said Dr. Niels
      Dingemanse of the University of Groningen, a collaborator Dr. Drent.

      Instead of questionnaires, the Dutch team tests the behavior of the
      birds to measure their personalities. In one test, the scientists place
      a strange object - a penlight battery or a Pink Panther doll - in a
      bird's cage. Some birds are quick to approach it, while others hang back.

      In another experiment, the researchers open a cage door, allowing the
      birds to explore a large room filled with five artificial trees. Some
      birds are quick to explore the trees, while others prefer to remain in
      the comforts of their cage.

      In a third experiment, the researchers place a bowl of tasty mealy worms
      in the room. When the birds land on the bowl to eat, the researchers
      startle the birds by lifting up a nearby metal plate. They then see how
      much time passes before the bird returns to the bowl.

      The tests revealed that the birds have consistent personalities that
      remain stable for years. Bold birds, as the scientists call them, are
      quick to inspect new objects, to explore the trees and to recover from
      the metal-plate surprise.

      Shy birds are slow on all three counts. The differences go well beyond
      these tests. Bold birds are also more aggressive than shy ones and
      experience less stress when the scientists handle them.

      Breeding experiments revealed that these traits had a strong genetic
      basis. Over just four generations, the researchers could produce
      significantly bolder and shyer birds. "About 50 percent of the variation
      you find in avian personalities is due to differences in genes," said
      Dr. Kees van Oers of the Max Planck Institute for Ornithology in Germany.

      Dr. van Oers is searching for the genes responsible for these
      differences. He estimates that as many as 10 may play an important role,
      and he has already pinpointed one strong candidate, known as DRD4.

      Some studies on the human version of this gene suggest that it
      influences how much people seek out new experiences. But other studies
      have failed to replicate the link. "We're still working on the last
      bits, but it looks promising," Dr. van Oers said.

      The genes for both bold and shy traits have been preserved by natural
      selection. To find out how this happens, the researchers have observed
      how birds with different traits have fared over the years. "We were not
      sure how the data would turn out because no one had collected them
      before," said Dr. Dingemanse, who led this part of the study.

      The researchers found that the personality of birds had a powerful
      effect on their survival, but that effect changed from year to year as
      the supply of food fluctuated. "It's quite a complex story," Dr.
      Dingemanse said. In lean years, for example, bold female birds had a
      better chance of surviving than shy ones, while shy males did better
      than bold ones. Those patterns switched during years with abundant food.

      Over the course of several years, however, birds with intermediate
      personalities appear to have had more success at bearing young. "Animals
      in the middle did better," Dr. Dingemanse said.

      If intermediate birds are better adapted than very bold or shy ones, it
      is strange that all the birds are not intermediate. One possibility is
      intermediate personalities arise when birds inherit a "bold" version of
      certain genes from one parent and a "shy" version from the other.

      Since a bird has a 50 percent chance of inheriting a gene from its
      mother or father, it's inevitable that some will wind up with two "shy"
      genes or two "bold" ones. As a result, they may get extreme personalities.

      Another idea the Dutch scientists want to explore is that the social
      life of birds helps bold and shy personalities to coexist.

      Each year the birds fight for territory where they can feed and breed.
      Bold birds are more aggressive than shy ones, and that sometimes helps
      them win territory. But the scientists have found that when bold birds
      lose, they are slow to recover. They end up at the bottom of the
      hierarchy, and in many cases just fly away. "They go to other places to
      try to become No. 1," Dr. Drent said.

      This struggle might balance the birds between bold and shy
      personalities. If there are a lot of shy birds, the few bold ones will
      rise to the top. But if there are a lot of bold birds, they will fight a
      lot, and that will result in a lot of bold birds flying away. In these
      cases, the few shy birds will thrive. "So one of the personalities can
      never disappear completely," Dr. Drent said.

      He and his colleagues plan to test this hypothesis by altering the ratio
      of bold and shy birds in the wild.

      Many of the findings are summarized in the February issue of
      Neuroscience and Biobehavioral Reviews.

      Researchers studying animal personality hope that their work will yield
      some practical benefits. Dr. Gosling and his students, for example, have
      been focusing much of their research on the personalities of dogs.

      An accurate test of dog personality may help animal shelters match pets
      to families. It may also help identify dogs that are especially well
      suited to jobs like detecting explosives.

      Studies on animal personality may also illuminate human personality. The
      Dutch researchers are now beginning to compare their research on birds
      to research carried out on children.

      "It was amazing how the way they measured the boldness of the birds
      resembles tests we have for young children," said Dr. Marcel van Aken, a
      psychologist at the University of Utrecht. He and the bird researchers
      plan to measure the personalities of birds and humans with a common set
      of tests, hoping to find clues to the evolution of human personality.

      Barely any research has been carried out on the evolution of human
      personality, but what little there is suggests that it may have some
      parallels with what's happened in birds.

      In a survey of 545 people, Dr. Daniel Nettle of the University of
      Newcastle in England found that the more extroverted people were, the
      more sex partners they tended to have had. That might give them an
      evolutionary edge, but Dr. Nettle found that they were also more likely
      to wind up in a hospital.

      Dr. Nettle is reporting his findings in a paper to be published in
      Evolution and Human Behavior.

      Some experts on human personality remain skeptical. Dr. Daniel Cervone
      of the University of Illinois at Chicago considers describing animals
      with terms like extroversion as "extremely risky." The word inevitably
      means something different when applied to a human or a bird.

      "There's a whole load of human qualities that simply weren't going into
      the ratings in the first place," he said.

      Dr. van Aken agrees that anthropomorphism is a real danger, but he
      thinks it can be avoided. "I'm not so concerned about it," he says. "You
      have to define clearly what you are going to measure and then let the
      data speak."


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