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Mirror neurons and imitation learning as driving force

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  • jeroen
    http://www.jodkowski.pl/we/VSRamachandran001.html It s a very interesting talk by V.S. Ramachandran on the neurological foundation of human communication,
    Message 1 of 1 , Mar 19, 2004

      It's a very interesting talk by V.S. Ramachandran
      on the neurological foundation of human communication,
      learning and culture.



      Unlike many other human traits such as humor,
      art, dancing or music the survival value of
      language is obvious - it helps us communicate our
      thoughts and intentions. But the question of how
      such an extraordinary ability might have actually
      evolved has puzzled biologists, psychologists and
      philosophers at least since the time of Charles
      Darwin. The problem is that the human vocal apparatus
      is vastly more sophisticated than that of any ape but
      without the correspondingly sophisticated language
      areas in the brain the vocal equipment alone would
      be useless.
      So how did these two mechanisms with so many
      sophisticated interlocking parts evolve in tandem?
      Following Darwin's lead I suggest that our vocal
      equipment and our remarkable ability to modulate
      voice evolved mainly for producing emotional calls
      and musical sounds during courtship ("croonin a
      toon."). Once that evolved then the brain - especially
      the left hemisphere - could evolve language.

      But a bigger puzzle remains. Is language mediated
      by a sophisticated and highly specialized "language
      organ" that is unique to humans and emerged
      completely out of the blue as suggested by Chomsky?
      Or was there a more primitive gestural communication
      system already in place that provided a scaffolding for
      the emergence of vocal language?

      Rizzolatti's discovery can help us solve this age-old
      puzzle. He recorded from the ventral premotor area
      of the frontal lobes of monkeys and found that
      certain cells will fire when a monkey performs a
      single, highly specific action with its hand: pulling,
      pushing, tugging, grasping, picking up and putting
      a peanut in the mouth etc. different neurons fire
      in response to different actions. One might be tempted
      to think that these are motor "command" neurons,
      making muscles do certain things; however, the
      astonishing truth is that any given mirror neuron will
      also fire when the monkey in question observes another
      monkey (or even the experimenter) performing the
      same action, e.g. tasting a peanut! With knowledge of
      these neurons, you have the basis for understanding
      a host of very enigmatic aspects of the human mind:
      "mind reading" empathy, imitation learning, and even
      the evolution of language. Anytime you watch someone
      else doing something (or even starting to do something),
      the corresponding mirror neuron might fire in your brain,
      thereby allowing you to "read" and understand another's
      intentions, and thus to develop a sophisticated "theory of
      other minds." (I suggest, also, that a loss of these mirror
      neurons may explain autism - a cruel disease that afflicts
      children. Without these neurons the child can no longer
      understand or empathize with other people emotionally
      and therefore completely withdraws from the world socially.)

      Mirror neurons can also enable you to imitate the
      movements of others thereby setting the stage for
      the complex Lamarckian or cultural inheritance that
      characterizes our species and liberates us from the
      constraints of a purely gene based evolution. Moreover,
      as Rizzolati has noted, these neurons may also enable
      you to mime - and possibly understand - the lip and
      tongue movements of others which, in turn, could
      provide the opportunity for language to evolve. (This
      is why, when you stick your tongue out at a new born
      baby it will reciprocate! How ironic and poignant
      that this little gesture encapsulates a half a million
      years of primate brain evolution.) Once you have
      these two abilities in place the ability to read someone's
      intentions and the ability to mime their vocalizations
      then you have set in motion the evolution of language.
      You need no longer speak of a unique language
      organ and the problem doesn't seem quite so mysterious
      any more.

      (Another important piece of the puzzle is Rizzolatti's
      observation that the ventral premotor area may be a
      homologue of the "Broca's area" - a brain center
      associated with the expressive and syntactic aspects of
      language in humans).

      These arguments do not in any way negate the idea
      that there are specialized brain areas for language
      in humans. We are dealing, here, with the question
      of how such areas may have evolved, not whether they
      exist or not.

      Mirror neurons were discovered in monkeys but how
      do we know they exist in the human brain? To find out
      we studied patients with a strange disorder called
      anosognosia. Most patients with a right hemisphere
      stroke have complete paralysis of the left side of their
      body and will complain about it, as expected. But about
      5% of them will vehemently deny their paralysis even
      though they are mentally otherwise lucid and intelligent.
      This is the so called "denial" syndrome or anosognosia.
      To our amazement, we found that some of these patients
      not only denied their own paralysis, but also denied the
      paralysis of another patient whose inability to move his
      arm was clearly visible to them and to others. Denying
      ones one paralysis is odd enough but why would a patient
      deny another patient's paralysis? We suggest that this
      bizarre observation is best understood in term of damage
      to Rizzolatti's mirror neurons. It's as if anytime you want
      to make a judgement about someone else's movements
      you have to run a VR (virtual reality) simulation of the
      corresponding movements in your own brain and without
      mirror neurons you cannot do this.



      My suggestion that these neurons provided the initial
      impetus for "runaway" brain/ culture co-evolution in
      humans, isn't quite as bizarre as it sounds. Imagine
      a martian anthropologist was studying human evolution
      a million years from now. He would be puzzled (like
      Wallace was) by the relatively sudden emergence of
      certain mental traits like sophisticated tool use, use
      of fire, art and "culture" and would try to correlate them
      (as many anthropologists now do) with purported changes
      in brain size and anatomy caused by mutations. But
      unlike them he would also be puzzled by the enormous
      upheavals and changes that occurred after (say) 19th
      century - what we call the scientific/industrial revolution.
      This revolution is, in many ways, much more dramatic
      (e.g. the sudden emergence of nuclear power, automobiles,
      air travel, and space travel) than the "great leap forward"
      that happened 40,000 years ago!!

      He might be tempted to argue that there must have been
      a genetic change and corresponding change in brain
      anatomy and behavior to account for this second leap
      forward. (Just as many anthropologists today seek a genetic
      explanation for the first one.) Yet we know that present one
      occurred exclusively because of fortuitous environmental
      circumstances, because Galileo invented the "experimental
      method," that, together with royal patronage and the invention
      of the printing press, kicked off the scientific revolution.
      His experiments and the earlier invention of a sophisticated
      new language called mathematics in India in the first
      millennium AD (based on place value notation, zero and
      the decimal system), set the stage for Newtonian mechanics
      and the calculus and "the rest is history" as we say.

      Now the thing to bear in mind is that none of this need have
      happened. It certainly did not happen because of a genetic
      change in the human brains during the renaissance. It happened
      at least partly because of imitation learning and rapid "cultural"
      transmission of knowledge. (Indeed one could almost argue
      that there was a greater behavioral/cognitive difference between
      pre-18th century and post 20th century humans than between
      Homo Erectus and archaic Homo Sapiens. Unless he knew better
      our Martian ethologist may conclude that there was a bigger
      genetic difference between the first two groups than the latter
      two species!)

      Based on this analogy I suggest, further, that even the first
      great leap forward was made possible largely by imitation
      and emulation. Wallace's question was perfectly sensible;
      it is very puzzling how a set of extraordinary abilities seemed
      to emerge "out of the blue". But his solution was wrong...the
      apparently sudden emergence of things like art or sophisticated
      tools was not because of God or "divine intervention". I would
      argue instead that just as a single invention (or two) by Galileo
      and Gutenberg quickly spread and transformed the surface of
      the globe (although there was no preceding genetic change),
      inventions like fire, tailored clothes, "symmetrical tools", and
      art, etc. may have fortuitously emerged in a single place and
      then spread very quickly. Such inventions may have been made
      by earlier hominids too (even chimps and orangs are remarkably
      inventive...who knows how inventive Homo Erectus or Neandertals
      were) but early hominids simply may not have had an advanced
      enough mirror neuron system to allow a rapid transmission and
      dissemination of ideas. So the ideas quickly drop out of the
      "meme pool". This system of cells, once it became sophisticated
      enough to be harnessed for "training" in tool use and for reading
      other hominids minds, may have played the same pivotal
      role in the emergence of human consciousness (and replacement
      of Neandertals by Homo Sapiens) as the asteroid impact did
      in the triumph of mammals over reptiles.

      So it makes no more sense to ask "Why did sophisticated tool
      use and art emerge only 40,000 years ago even though the
      brain had all the required latent ability 100,000 years earlier?"
      - than to ask "Why did space travel occur only a few decades
      ago, even though our brains were preadapted for space travel
      at least as far back Cro Magnons?". The question ignores the
      important role of contingency or plain old luck in human evolutionary

      Thus I regard Rizzolati's discovery - and my purely speculative
      conjectures on their key role in our evolution - as the most important
      unreported story of the last decade.
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