The development of a smoothly controlled motor system is a major childhood priority. Suckling is almost the first mobile act of an infant, followed by the brain-outward maturation of the arm and leg systems—eating before grasping before walking. Since mobility is a central human characteristic, these innate systems must develop early at the survival level without formal instruction. This motor development includes specific currently ill understood periods during which various key specialized brain systems generally develop (such as walking at about one, talking at about two).
How infants begin their mastery of complex motor behaviors is a fascinating developmental phenomenon. Consider a behavior that most parents observe. If you stick out your tongue to an observant infant shortly after birth, the probability is high that she will reciprocate the behavior.
Sticking out our tongue is an uncommon act for humans, and it requires the activation of a complex motor neuron sequence. Our tongue is a very important muscle that is used to facilitate eating and speech, so we normally keep it inside our mouth. I suppose it would be possible for an infant to randomly fire the appropriate motor neurons for tongue projection, but that’s not what occurs when an infant sticks out her tongue in immediate mimicry of a parent’s action. How can an infant possibly master such a complex motor act immediately after observing it?
Scientists have discovered a remarkable system they call mirror neurons that explains the modeling/mimicking process that is central to much human learning. Their initial studies involved a left hemisphere area called Broca’s Area that regulates speech production. In a presentation at Cambridge University that was posted on the Internet, the renowned neuroscientist V. S. Ramachandran (2000) suggested that the discovery of mirror neurons might provide the same powerful unifying framework for our understanding of teaching and learning that the discovery of DNA did for our understanding of genetics.
A smoothly coordinated motor sequence involves the typically unconscious preparation for a movement followed by the actual movement. For example, while my left index finger is typing the c in cat, my left little finger is getting ready to type a and my left index finger will shortly move up to the top row to type the t. The result is a single seamless typing action – cat.
The motor cortex plays a key role in activating such muscles. It’s a narrow ear-to-ear band of neural tissue, with specific segments dedicated to regulating specific groups of body muscles. The premotor area directly in front of the motor cortex primes the next movements in a motor sequence.
Scientists have recently discovered that neurons in the premotor area that fire in preparation for upcoming movements also fire when we observe someone else carry out that action (Meltzoff and Prinz, 2002). Common brain regions thus process both the perception and production of a movement. The infant’s observation of her parent’s projecting tongue fires the premotor neurons that represent her tongue and this priming activates the related motor cortex neurons that project her tongue out in mimicry.
We experience this mimicking phenomenon most commonly when we see someone yawn, and then typically have to stifle our own yawn. Since infants must learn many movements, they don’t inhibit the mimicking of movements they observe. For them it’s monkey see, monkey do (and it’s interesting that the initial mirror neuron research was done on monkeys).
Our mirror neurons won’t fire at the mere observation of a hand or mouth—only when its carrying out a goal directed action. Further, they will respond to a hand but not a tool that’s grasping or moving an object (since body parts and not tools are represented in our motor/premotor areas).
Mirror neurons may thus facilitate the preliminary motor neuron simulation, priming, programming, and rehearsing that occurs in children, and this process obviously enhances our eventual mastery of complex motor behaviors, and our ability to read the minds of others. For example, inferring the potential movements of others is an essential skill in many games in which players try to fake out opponents. Mirror neuron stimulation may also explain why so many people enjoy observing the movements of virtuoso athletes, dancers, and musicians. It allows us to mentally represent actions we can’t physically mimic. Note the related active body language of former athletes as they observe a game they once played.
Scientists are also exploring the relationship between mirror neuron activity and our ability to imagine our own planned actions, be empathetic, and develop articulate speech. Mirror neurons may thus eventually help to explain many teaching and learning mysteries in which modeling provides children with an effective behavioral pattern to follow—and to explain disabilities (such as autism) in which children can’t read the minds of others.
Children denied the opportunity to observe and thus develop a motor-driven survival skill that they would normally master with ease during its preferred developmental period may not recover from the deprivation. A good example is the tragic case of Genie, who was 13 when discovered hidden naked in a closet. Her mentally disturbed parents had almost totally deprived her of normal language and motor development. Competent therapists who then tried to undo the damage were only marginally successful (Rymer, 1993).
Mirror neurons may well become this century’s equivalent of the mid-20th century discovery of DNA.