Human Mirror Neurons

After the initial monkey research, neuroscientists used neuroimaging technologies to study mirror neurons in humans. These studies have already resulted in fascinating discoveries that are changing how we view many elements of human life. These elements include the development of articulate speech; the underlying mechanisms of empathy; maladies such as autism; the broad appeal of observing others who are engaged in sports, dance, or musical performance; and the effects of electronic media on behavior.

We humans have an incredibly complex mirror neuron system that encompasses our entire sensory system, that allows us to simulate the emotional lives of others, and that thus drives our rich cultural life.

When we observe someone yawn, it activates our brain's yawning system. Adults typically override the tendency and stifle the yawn—but if we stick out our tongue at an infant who is only a few hours old, it's probable that she will immediately reciprocate, even though she had never before stuck out her tongue (or even had any conscious awareness of her tongue). Her observation of our behavior will automatically activate the mirror neurons that regulate her tongue movements. Since she has a zillion movements to learn and therefore no reason to stifle the action, her mirror neurons will activate the motor neurons that project her tongue. Similarly, smile and she'll smile. Clap your hands and she'll clap her hands. It's like monkey see, monkey do in childhood.

Speech. Language is a key element of human movement. We can use our legs to approach a friend and extend our hand for a handshake greeting—but we can also stay where we are and project rhythmic air patterns via mouth/tongue movements. These sound patterns activate ear and brain activity that our friend interprets as a verbal greeting. Written language and music are thus also forms of communicative movement.

We can observe arm/leg movements, but not what's occurring inside the mouth of a speaker. The mirror neuron system helps to explain how a child learns to speak. Our sensory/motor system is highly interconnected, so we can visualize a named but non-visible object, such as a banana. Similarly, hearing articulate speech activates the same speech processes in the child's brain that the speaker used to sequence sounds and words. Speech is a complex motor activity, so the infant initially babbles incoherently, but over time in a verbal environment, the child begins to correctly utter simple phonemic combinations, and finally smooth articulate speech emerges.

When we observe someone in the initial stages of a movement sequence, such as when a diner picks up a knife and fork, we infer the subsequent actions because our brain is mirroring the sequence and so knows what will occur next. When a speaker stops mid-sentence, we can often complete the sentence. Athletes fake out an opponent's mirror neuron system by beginning an action, and then quickly and unexpectedly switching to a different action.