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Seeing isn't always needed for believing, study indicates

Betsy Mason | Dallas Morning News Posted August 12, 2001

The old saying "monkey see, monkey do" is getting a new twist from
scientists who say the monkey may not need to see after all.

Monkeys and other primates, including humans, have specialized brain cells
that act like an internal mirror. These cells, aptly dubbed "mirror
neurons," are active when a monkey does something such as grasp a block and
also when the monkey sees someone else grasp a block.

New research shows that the mirror neurons also fire when the experimenter
grasps a block that is hidden from view, as long as the monkey can assume
the block is there.

"When I see a girl eating an apple, I understand what she is doing because
there is activation of a motor mechanism in my brain. In other words, I am
doing in my brain the same thing the girl does. I am in her shoes, as
people say," says Giacomo Rizzolatti, a psychologist from the University of
Parma in Italy and an author of the study.

"The new data show that this mechanism is active also when we, or monkeys,
do not see the action but only guess what it might be," says Rizzolatti.

The researchers tested the brains of two macaque monkeys, using electrodes
to record the response of individual mirror neurons. The monkeys watched a
person grasp a block in full view or grasp a block that was behind a
screen. As long as the monkey had reason to believe the block was behind
the screen, the mirror neurons responded.

"The monkey has to know about the goal to recognize the action, but it
doesn't have to see the goal," says Michael Arbib of the University of
Southern California, who also studies mirror neurons.

In one experiment, the monkey saw that the block was not behind the screen.
The experimenter then reached behind the screen as if to grasp the block,
and the neurons did not respond. Also, when the screen was removed, the
neurons were not triggered by the block without the action, or by the
action without the block.

The mirror neurons may represent the basic circuitry that primates use to
function in a society. "You're not going to make a society with individuals
you don't understand," says Marco Iacoboni, a neuroscientist from the
University of California, Los Angeles. "We think, with this very simple
mechanism, you can understand the actions of others and the intentions of
others."

Humans may use mirror neurons for more complicated social interactions. The
mirror neuron region in the monkey's brain corresponds to one of the
language centers of the human brain called Broca's area. Rizzolatti and
Arbib speculate that mirror neurons may be the biological basis of the
mysterious evolution of human language. Just as they allow us to understand
what others are doing, they may somehow enable us to understand what others
are saying.

"We may have found the missing link," says Arbib.

The correlation between a motor center in monkeys and a language center in
humans lends support to the theory that sign language may have been an
important step in the evolution of language, says Arbib.

Iacoboni and Rizzolatti believe the research may help solve other puzzles,
such as autism. Kids with autism don't do well at imitating others, says
Iacoboni. "It's possible that autistic kids have a deficit in the function
of mirror neurons."

Social animals other than primates may have mirror neurons, as well, but
this idea has yet to be researched.

"There's still a lot to be done with monkeys before we move on to other
species," says Iacoboni. "But it will happen."