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Some apes, birds can think ahead - studies (Reuters) Updated: 2006-05-19 10:44
WASHINGTON - Apes that remember to carry the right tools to retrieve treats
and scrub jays that hide food a second time when they think a rival is watching
prove animals can think ahead -- a trait once believed to be uniquely human,
scientists have found.
A Chimpanzee eats
peanuts in its cage at Argentina's Buenos Aires Zoo, February 15, 2006.
Scientists have found that some apes and birds could also plan for the
future. [Reuters] | Two carefully planned sets of experiments to be
published on Friday in the journal Science show intelligent birds and great apes
can plan into the future in a way that transcends simple food caching, as
squirrels, foxes and other animals do.
"Planning for future needs is not
uniquely human," Thomas Suddendorf of the University of Queensland in Brisbane,
Australia, wrote in a commentary.
"Apes and jays can also anticipate
future needs by remembering past events, contradicting the notion that such
cognitive behavior only emerged in hominids."
In one experiment,
Nicholas Mulcahy and Josep Call of the Max Planck Institute for Evolutionary
Anthropology in Leipzig, Germany, tested bonobos, close relatives of
chimpanzees, and orangutans at the local zoo.
They set up several
experiments that required the apes to remember a complex way to retrieve a treat
and offered them the opportunity to use tools to do so.
So far,
observations of tool use and planning have involved only immediate hunger on the
part of the animals, which does not involve long-term thinking, Mulcahy and Call
argued.
"Thus, when chimpanzees transport stones to use them to crack
open nuts, or New Caledonian crows make hook-shaped tools to fish for insects,
they do so in an attempt to satisfy their current hunger state, not some future
one," they wrote.
In one experiment, they rigged up a metal cylinder
with a piece of uncooked spaghetti holding two bunches of grapes.
"To
obtain the reward subjects had to break the spaghetti by inserting a plastic
tube through the top hole over the cylinder. That caused the grapes to fall down
and hang in front of the bottom holes thus allowing subjects access to them,"
the researchers wrote.
In another test, the apes had to use a metal hook
to fish out a bottle of grape juice.
To pass the tests, the apes had to
remember to bring the right tool out of the room with them, and bring it back
with them some time later. Both orangutans and bonobos passed the tests several
times, the researchers said.
'NOT A UNIQUELY HUMAN
ABILITY'
"Together with recent evidence from scrub jays, our
results suggest that future planning is not a uniquely human ability, thus
contradicting the notion that it emerged in hominids only within the past 2.5 to
1.6 million years," Mulcahy and Call wrote.
Joanna Dally of the
University of Cambridge in Britain and colleagues tested captive scrub jays, and
saw the birds could remember which other birds were watching them when they
first hid some treats.
If a bird dominant to the jays saw them store
their food, the jays would move the cache later when the dominant bird was not
watching.
But if the bird allowed to watch the treat being hidden was
subordinate, or a mate, the jays did not later re-cache their food -- presumably
because they could fight off subordinates that try to steal their food, the
researchers wrote.
"These results suggest scrub-jays remember who
observed them make specific caches," Dally's team wrote.
Jays are
members of a group of birds called corvids, which include crows, jays and ravens
and which biologists consider to be the most intelligent species of
bird.
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