traditionally been treated as antagonistic to each other, or at least mutually
exclusive. But today, in the new discipline of social neuroscience,
the assumption is that a multilevel integrative analysis may be required
and that a common scientific language, grounded in the structure and
function of the brain, can contribute to it. The self-model theory is an
attempt to develop exactly this type of language.
It has been known since the 1980s that there is a particularly interesting
class of neurons in an area called F5 in the ventral premotor region
of the monkey brain. These neurons are part of the unconscious selfmodel;
they code body movements in a highly abstract way. Giacomo
Rizzolatti, a professor of human physiology at the University of Parma
and a pioneer in this exciting field of research, uses the concept of a
“motor vocabulary” that consists of complex inner images of actions as a
whole. Words in the monkey’s motor vocabulary might be “reach,”
“grasp,” “tear,” or “hold.” The interesting aspect of this discovery is that
there is a specific part of the brain that describes the monkey’s—and our
own—actions in a holistic manner. This description includes the goals
of the actions and the temporal pattern in which the actions unfold. The
actions are portrayed as relations between an agent and the target object
(a piece of fruit, say) of his action. Now we know that human beings, too, possess something similar.
From a neurocomputational perspective, this system in our brains
makes sense: By developing an inner vocabulary for possible actions, we
reduce the immense space of possibilities to a small number of stereotypical
body movements. This allows us, for instance, to perform the
same grasping movement in widely differing situations (recall the Alien
Hand syndrome of chapter 4). One of the most fascinating features of these so-called canonical
neurons is that they also respond to the visual perception of objects in
our environment. Our brain does not simply register a chair, a teacup,
an apple; it immediately represents the seen object as what I could do
with it—as an affordance, a set of possible behaviors. This is something I
could sit on, this is something I could hold in my hands, this is something
I could throw. While we’re seeing an object, we are also unconsciously
swimming in a sea of possible behaviors. As it turns out, the
traditional philosophical distinction between perception and action is
an artificial one. In reality, our brains employ a common coding: Everything
we perceive is automatically portrayed as a factor in a possible interaction
between ourselves and the world. A new medium is created,
blending action and perception into a novel, unified representational format.
The second fascinating discovery about canonical neurons is that
you also use them for self-representation. The motor vocabulary is part
of the unconscious self-model, because it describes the goal-directed
movements of one’s body. The unconscious precursors of the phenomenal
Ego in our brain thus play an essential and central role in our perception
of the world around us.
In the 1990s, researchers discovered another group of neurons.
Also a part of area F5, they fire not just when monkeys perform objectdirected
actions, such as grasping a peanut, but also when they observe
others performing the same type of action. Because these neurons respond
to actions performed by others, they are termed mirror neurons.
They are activated when another agent is observed using objects in a
purposeful way. Thus, we are matching the bodily behaviors we observe
in others with our own internal motor vocabulary. This action/
observation matching system helps us understand something we
could never understand using our sensory organs alone—that other beings
in our environment pursue goals. We use our own unconscious
self-model to put ourselves in the shoes of others, as it were. We use
our own “motor ideas” to understand someone else’s actions by directly
mapping them onto our own inner repertoire, by automatically triggering
an inner image of what our goal would be if our body also moved
that way. The conscious experience of understanding another human being, the subjective feeling that pops up in the Ego Tunnel when we intuitively
grasp what others’ goals are and what is going on in their
minds, is the direct result of these unconscious processes. The conscious self is thus not only a window into the internal workings
of one’s own Ego but also a window into the social world. It is a
two-way window: It elevates to the level of global availability the unconscious
and automatic processes that organisms constantly use to represent
one another’s behavior. This is how these processes become part of
the Ego Tunnel, an element of our subjective reality. They lead to an
enormous expansion and enrichment of our inner simulation of the
world. As soon as our brains are able to represent not only events but
also actions—that is, goal-directed events caused by other beings—we
are not alone anymore. Others exist, with minds of their own. The fact
that more than one Ego Tunnel might exist in the world is now reflected
in our own tunnel. We can develop our conscious-action ontology, and
we can put it to use by sharing it with others. A considerable body of evidence using a variety of neuroimaging
techniques shows that the mirror-neuron system exists not just in monkeys
but in humans as well. However, it appears that the system in humans
is much more generalized and does not depend on concrete
effector-object interactions; consequently, it can represent a much
greater variety of actions than it does in monkeys. In particular, researchers
have now discovered mirror-neuron systems that seem to
achieve similar effects for emotions and for pain and other bodily sensations.
When human test subjects are shown pictures of sad faces, for example,
they subsequently tend to rate themselves as sadder than they
were before—and after being shown happy faces they tend to rate themselves
as happier. Converging empirical data show that when we observe
other human beings expressing emotions, we simulate them with the
help of the same neural networks that are active when we feel or express
these emotions ourselves. For instance, certain regions in the insular
cortex are activated when subjects are exposed to a disgusting smell,
and the same regions are active when we see an expression of disgust on
another person’s face. A common representation of the emotional state
of disgust is activated in our brains whether we experience it ourselves or observe it in another individual. Parallel observations in the amygdala
have been made for fear. It is interesting to note that our ability to recognize
a particular feeling in another human being can be weakened or
switched off by blocking the relevant parts of the mirror-neuron system.
It is believed, for example, that certain areas in the ventral striatum of
the basal ganglia are necessary in recognizing anger; patients with damage
to this area show impairment in identifying aggression signals emitted
by others. If these areas are blocked pharmacologically (by
interfering with dopamine metabolism), subjects can recognize other
emotions but can no longer recognize anger. Similar observations have
been made for pain. Recent fMRI (functional magnetic resonance imaging)
experiments show that areas in the anterior cingulate cortex and
the interior insular cortex are active when we experience pain but also
when we observe someone else experiencing pain. Interestingly, only
the emotional part of the pain system is activated; the part associated
with the purely sensory aspect of pain is not. This makes perfect sense,
because the sensory aspect is exactly what we cannot share with anyone
else: We cannot share the cutting, throbbing, or burning sensory quality
of pain, but we can feel empathy with regard to the emotions it causes.
Other neuroimaging experiments have demonstrated that a similar
principle exists for other bodily sensations. Certain higher levels of the
somatosensory cortex are activated both when subjects observe others
being touched and when they are touched themselves. Again, the immediate
sensory quality associated with the activation of the primary somatosensory
cortex cannot be shared, but a higher level in the bodily
Ego is active regardless of whether we are being touched or just observing
someone being touched. There seems to be an underlying principle
uniting these new empirical discoveries: Certain layers of our self-model
function as a bridge to the social domain, because they can directly map
abstract inner descriptions of what is going on in ourselves onto those of
what goes on in other people.
Of course, intersubjectivity is not only about the body and emotions.
Thinking plays a role as well. Reason-based forms of empathy
appear to involve yet other parts of the brain—specifically, the ventromedial
prefrontal cortex. Still, the discovery of mirror neurons helps us to understand that empathy is a natural phenomenon, acquired step by
step in the course of our biological evolution. First, we developed the
self-model, because we had to integrate our sensory perceptions with
our bodily behavior. Then this self-model became conscious, and the
phenomenal self-model was born into the Ego Tunnel, allowing us to
achieve global control of our bodies in a much more selective and flexible
manner. This was the step from being an embodied natural system
that has and uses an internal image of itself as a whole to a system that,
in addition, consciously experiences this fact. The next evolutionary
step was what Vittorio Gallese, Rizzolatti’s colleague at Parma and one
of the leading researchers in the field, has called embodied simulation.In order to understand the feelings and goals of other human beings, we
use our own body-model in the brain to simulate them.
As recent neuroscientific findings show, this process also cuts across
the border between the unconscious and the conscious. A considerable
part of this constant mirroring activity happens outside the Ego Tunnel,
and thus we have no subjective experience of it. But from time to time,
when we deliberately attend to other people or analyze social situations,
the conscious self-model is involved as well; in particular, as noted, we
can somehow directly comprehend, almost perceive, what somebody
else is up to. Often, we “just know” what the purpose of the other person’s
action is and what his likely emotional state is. We use the same
internal resources that make us aware of our own goal states to discover
automatically that others are goal-directed entities themselves and not
just other moving objects. We can experience them as Egos because we
experience ourselves as Egos. Whenever successful social understanding
and empathy are achieved, we share a common representation: of
one and the same goal state in two different Ego Tunnels. Social cognition
has now become tractable to empirical neuroscience on the level of
single-cell recordings—showing us not only how Ego Tunnels started to
resonate with each other but also how complex cooperation and communication
between self-conscious organisms were able to evolve and
lay the foundations for cultural evolution.
My idea is that social cognition rests on what is sometimes called an
exaptation. Adaptation led to an integrated body-model in the brain and to the phenomenal self-model. Then the existing neural circuitry
was “exapted” for another form of intelligence: It suddenly proved useful
in tackling a different set of problems. This process began with loworder
motor resonance; then, second- and third-order embodiment led to embodied simulation as a brand-new tool in developing social
intelligence. Like everything else in evolution, this process was driven
by chance. There was no purpose behind it, but it eventually led us
where we are today—to the formation of intelligent, scientific communities
peopled by conscious agents trying to understand this very
process itself.
The new emerging general picture is inspiring: We are all constantly
swimming in an unconscious sea of intercorporality, permanently mirroring
one another with the aid of various unconscious components and
precursors of the phenomenal Ego. Long before conscious, high-level
social understanding arrived on the scene, and long before language
evolved and philosophers developed complicated theories about what it
takes for one human being to acknowledge another as a person and a rational
individual, we were already bathed in the waters of implicit, bodily
intersubjectivity. Few great social philosophers of the past would
have thought that social understanding had anything to do with the premotor
cortex, and that “motor ideas” would play such a central role in
the emergence of social understanding. Who could have expected that
shared thought would depend upon shared “motor representations”?
Or that the functional aspects of the human self-model that are necessary
for the development of social consciousness are nonconceptual,
pre rational, and pretheoretical? The first inklings of these ideas came at
the end of the nineteenth and the first half of the twentieth century,
when there were numerous attempts in experimental psychology to better
understand so-called ideomotor phenomena. Philosopher Theodor
Lipps wrote about Einfühlung (empathy) in 1903—that is, the ability, as
he put it, to “feel yourself in an object.” He had already spoken of “inner
imitation” and of “organic feelings.” For him, objects of empathy could
be not only the movements or postures we perceive in other human beings
but also objects of art, architecture, and even visual illusions. He
held that aesthetic pleasure was “objectified”—that is, “the object is ego and thereby the ego object.” Social psychologists began talking about
concepts such as “virtual body movements” and “motor mimicry” or
“motor infection” decades ago.
From a philosophical perspective, the discovery of mirror neurons is
exciting because it gave us an idea of how motor primitives could have
been used as semantic primitives: that is, how meaning could be communicated
between agents. Thanks to our mirror neurons, we can consciously
experience another human being’s movements as meaningful.
Perhaps the evolutionary precursor of language was not animal calls but
gestural communication. The transmission of meaning may initially
have grown out of the unconscious bodily self-model and out of motor
agency, based, in our primate ancestors, on elementary gesturing.
Sounds may only later have been associated with gestures, perhaps with
facial gestures—such as scowling, wincing, or grinning—that already
carried meaning. Still today, the silent observation of another human being
grasping an object is immediately understood, because, without symbols
or thought in between, it evokes the same motor representation in
the parieto-frontal mirror system of our own brain. As Professor Rizzolatti
and Dr. Maddalena Fabbri Destro from the Department of Neuroscience
at the University of Parma put it: “[T]he mirror mechanism
solved, at an initial stage of language evolution, two fundamental communication
problems: parity and direct comprehension. Thanks to the
mirror neurons, what counted for the sender of the message also counted
for the receiver. No arbitrary symbols were required. The comprehension
was inherent in the neural organization of the two individuals.”Such ideas give a new and rich meaning not only to the concepts of
“grasping” and “mentally grasping the intention of another human being,”
but, more important, also to the concept of grasping a concept—the
essence of human thought itself. It may have to do with simulating hand
movements in your mind but in a much more abstract manner. Humankind
has apparently known this for centuries, intuitively: “Concept”
comes from the Latin conceptum, meaning “a thing conceived,” which,
like our modern “to conceive of something,” is rooted in the Latin verb
concipere, “to take in and hold.” As early as 1340, a second meaning of
the term had appeared: “taking into your mind.” Surprisingly, there is a representation of the human hand in Broca’s area, a section of the human
brain involved in language processing, speech or sign production,
and comprehension. A number of studies have shown that hand/arm
gestures and movements of the mouth are linked through a common
neural substrate. For example, grasping movements influence pronunciation—
and not only when they are executed but also when they are observed.
It has also been demonstrated that hand gestures and mouth
gestures are directly linked in humans, and the oro-laryngeal movement
patterns we create in order to produce speech are a part of this link.
Broca’s area is also a marker for the development of language in human
evolution, so it is intriguing to see that it also contains a motor representation
of hand movements; here may be a part of the bridge that
led from the “body semantics” of gestures and the bodily self-model to
linguistic semantics, associated with sounds, speech production, and
abstract meaning expressed in our cognitive self-model, the thinking
self. Broca’s area is present in fossils of Homo habilis, whereas the presumed
precursors of these early hominids lacked it. Thus the mirror
mechanism is conceivably the basic mechanism from which language
evolved. By providing motor copies of observed actions, it allowed us to
extract the action goals from the minds of other human beings—and
later to send abstract meaning from one Ego Tunnel to the next.
The mirror-neuron story is attractive not only because it bridges
neuroscience and the humanities but also because it illuminates a host
of simpler social phenomena. Have you ever observed how infectious a
yawn is? Have you ever caught yourself starting to laugh out loud with
others, even though you didn’t really understand the joke? The mirrorneuron
story gives us an idea of how groups of animals—fish schools,
flocks of birds—can coordinate their behavior with great speed and accuracy;
they are linked through something one might call a low-level
resonance mechanism. Mirror neurons can help us understand why parents
spontaneously open their mouths while feeding their babies, what
happens during a mass panic, and why it is sometimes hard to break
away from the herd and be a hero. Neuroscience contributes to the image
of humankind: We are all connected in an intersubjective space of
meaning—what Vittorio Gallese calls a “shared manifold.”
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