- Monkeys can deduce what other monkeys and humans think,
want and see based on visual cues, according to a new paper.
-
- The study, in this week's issue of the journal Current
Biology, is the first to show that monkeys, like humans, not only react
to visual information, they can also use it to reason about the behaviour
of others.
-
- The findings suggest that certain human cognition skills
are not as rare as once thought.
-
- They also indicate that the ability to reason did not
evolve in humans. Instead, the brainy trait probably passed down to us
from our ape ancestors.
-
- US researchers studied a population of free-range rhesus
monkeys (Macaca mulatta) that live on the island of Cayo Santiago in Puerto
Rico.
-
- Despite their apprehension at getting close to humans,
the monkeys sometimes try to swipe food from visitors to the island when
the visitors are not paying attention.
-
- This inspired Jonathan Flombaum, a graduate student in
the psychology department at Yale University and colleague Assistant Professor
Laurie Santos to test the monkeys on their ability to assess the visual
perspectives of others.
-
- Grape expectations
-
- Flombaum and Santos devised six experiments. All involved
a human holding a grape next to a curious monkey. For the first experiment,
the human grape holder stood either facing the monkey or turned away from
it.
-
- In experiments two to five, the humans varied their positions
relative to the monkeys and altered the monkeys' view with platforms and
barriers.
-
- For the final experiment, the human held up a small rectangular
cut-out that blocked either the human's eyes or his mouth.
-
- The experiments revealed that the monkeys would snatch
grapes whenever the human could not see the monkey or when the human was
not paying attention to the fruit.
-
- Flombaum says that competition, in this case the desire
for food, triggers a monkey's powers of deduction.
-
- "What our studies certainly demonstrate is that
in situations where the animal does deduce what another individual sees,
that the animal uses the most reliable information in this context, namely,
where that individual's eyes, and not any other part of their head, are
pointing," he explains.
-
- "We know that cells in the monkey superior temporal
sulcus [part of the brain] encode this information.
-
- "So in the contexts that the animal does come to
deduce what another individual sees, the animal's brain just needs to ask
itself, 'What occupies the coordinates in the world where that other monkey's
or that person's eyes are pointing?'
-
- "In our experiments, for example, if the answer
the animal got was 'one of the grapes', then the animal knew this was not
a good grape to approach."
-
- Flombaum thinks other competitive situations could cause
monkeys to make deductions about the knowledge and perspectives of others.
For example, he says they might do this when trying to attract mates or
when protecting offspring.
-
- "If we are right that rhesus monkeys can 'mind read'
in the ways that we say they can, then our own similar abilities probably
did not evolve in us," Flombaum says.
-
- "Instead, we appear to have been lucky enough to
inherit them from our rhesus monkey and chimpanzee relatives."
-
- While Flombaum does not believe in true psychic phenomena,
he thinks that humans experience intuition based on such deductions; for
example, when a person gets a sudden feeling that a situation should be
avoided, or when a bad vibe suggests that someone is lying or staring,
even when the possible victim cannot be sure.
-
- Many of these skills are derived from the interchange
between visual information and the brain's ability to encode it.
-
- Linked with autism?
-
- People with autism appear to have a hyperactive amygdala,
part of the brain that deals with emotions and negative feelings.
-
- A study in the latest issue of the journal Nature Neuroscience
found that some autistic people tend to avoid making eye contact because
anyone, even a mother or friend, can be perceived as a potential threat.
-
- Flombaum believes that, in future, his work might help
scientists to learn more about autism, its possible causes and potential
treatments.
-
- Dr Brian Hare, a researcher and postdoctoral associate
at the Max Planck Institute for Evolutionary Anthropology, studies chimpanzees.
And he says the new monkey study presents "welcome findings".
-
- "The study on rhesus monkeys shows what many people
have suspected, but didn't have the beautiful data to back up their theories
with," Hare says.
-
- "I hope to see more of this type of work in future
because it is fun to learn more about monkeys and chimpanzees. This information
also can tell us what makes humans so special and interesting."
-
- Flombaum currently is testing monkeys with even trickier
constraints than before. He has a human "accidentally" roll grapes
down a ramp.
-
- During the experiments, the human or the ramp are blocked
in various ways that sometimes suggest to monkeys that the human does not
realise the grape has rolled away.
-
- So far, Flombaum says monkeys are making the expected
assumptions about what the human sees, using this clever guesswork to steal
quite a few grapes.
-
- ©2005 ABC
-
- http://abc.net.au/science/news/stories/s1318239.htm
|
