V.S. Ramachadran provides a fascinating discussion of mirror neurons in his book The Tell-Tale Brain. The chapter which introduces them is titled: “The Neurons that Shaped Civilization.” Ramachandran begins by trying to provide an answer to a few interesting questions. Data indicates that the human brain reached its current size about 300,000 years ago, but the emergence of the capabilities and attributes that we associate with humanity—tool making, art, and perhaps language— only began to emerge about 75,000 years ago. He asks why did it take so long, and once these capabilities began to appear, how did they develop so quickly?
One must bear in mind that genetic modification by natural selection is a very inefficient process. Pre-man had evolved by this process for millions of years. What explains a massive change in capability taking place over thousands of years? Ramachandran suggests that what happened is that the brain at some point achieved a critical level of capability to program itself. Once you are able to learn and transmit skills culturally rather than genetically, there is no physical limit on growth of capability. He assigns mirror neurons a central role in this process.
Mirror neurons were discovered fairly recently, in the 1990s, during studies of monkeys. It was observed that certain neural networks were activated when a monkey performed a given task, such as reaching for an object. That was not remarkable, but what the excited the researchers was the discovery that these same neural networks fired when the monkey observed another monkey performing the same task. The author claims he nearly jumped out of his chair when he first heard these observations being reported.
Many ramifications flow from these networks that came to be referred to as mirror neurons. The most significant is that it appears that the brain has developed an efficient mechanism for mimicking the actions of another. In fact, it appears that this tendency to mimic is so strong that a brain function has to exist to suppress it when necessary. The most straightforward benefit of this capability is that one can learn and imprint skills by observing others. This, when combined with a language capability, provides cultural inheritance that can be passed on to, and be amplified by, a succeeding generation.
Ramachandran states that these mirror neurons actually have a higher order function than just mimicry. In observing the actions of another we are actually running a simulation of what the other person might be intending to do. The brain sorts through the various options and delivers to our consciousness what it considers the most likely outcome. This process is continually reviewed and updated as more data comes in. If you add to the process the ability to ascertain emotional content in the facial expression and body language of another via the same learning process, then you have the makings of a modern social human.
The author surmises that these mirror neurons also played a role in the development of language. The ability to make specific sounds for specific reasons is common to many animals and probably developed genetically in man as well. This capability for mimicry would certainly have been useful in developing more complex means of communicating that involved sign language or manipulation of the tongue and lips to perform more complex and varied sounds.
Humans and monkeys both have mirror neurons. Why are our capabilities so much greater? The author touches on this by pointing out that humans have combined their mirror neurons with more complex functional capabilities in our brains. There are limits to what a monkey can learn by observation.
The author also points out that the extremely long learning period that human children experience is necessary to adequately program the brain to function as it needs to function. In fact, as the modern world gets more complex, human intellectual adolescence is getting stretched to later years. Some parents are beginning to suspect it might never end. Watching an infant slowly acquire capabilities is a wondrous experience, but probably few parents think of their child as a computer being programmed.
Ramachandran has subtitled his book “A Neuroscientist’s Quest for what Makes Us Human.” A more appropriate title might have been “A Neuroscientist’s Quest to Explain Everything.” There are few things the author does not address. Fortunately he is quite consistent in telling the reader when he is speculating and when he is talking solid science. It makes a great read.
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