Understanding Higher-Level Functions: Imitation, Prediction, and Emotion
Operations of thought are like cavalry charges in a battle—they are strictly limited in number, they require
fresh horses, and must only be made at decisive moments.
—A
LFRED
N
ORTH
W
HITEHEAD
But the big feature of human-level intelligence is not what it does when it works but what it does when it's
stuck.
—M
ARVIN
M
INSKY
If love is the answer, could you please rephrase the question?
—L
ILY
T
OMLIN
Because it sits at the top of the neural hierarchy, the part of the brain least well understood is the cerebral cortex. This
region, which consists of six thin layers in the outermost areas of the cerebral hemispheres, contains billions of
neurons. According to Thomas M. Bartol Jr. of the Computational Neurobiology Laboratory of the Salk Institute of
Biological Studies, "A single cubic millimeter of cerebral cortex may contain on the order of 5 billion ... synapses of
different shapes and sizes.” The cortex is responsible for perception, planning, decision making and most of what we
regard as conscious thinking.
Our ability to use language, another unique attribute of our species, appears to be located in this region. An
intriguing hint about the origin of language and a key evolutionary change that enabled the formation of this
distinguishing skill is the observation that only a few primates, including humans and monkeys, are able to use an
(actual) mirror to master skills. Theorists Giacomo Rizzolatti and Michael Arbib hypothesized that language emerged
from manual gestures (which monkeys—and, of course, humans—are capable of). Performing manual gestures
requires the ability to mentally correlate the performance and observation of one's own hand movements.
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Their
"mirror system hypothesis" is that the key to the evolution of language is a property called "parity," which is the
understanding that the gesture (or utterance) has the same meaning for the party making the gesture as for the party
receiving it; that is, the understanding that what you see in a mirror is the same (although reversed left-to-right) as
what is seen by someone else watching you. Other animals are unable to understand the image in a mirror in this
fashion, and it is believed that they are missing this key ability to deploy parity.
A closely related concept is that the ability to imitate the movements (or, in the case of human babies, vocal
sounds) of others is critical to developing language.
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Imitation requires the ability to break down an observed
presentation into parts, each of which can then be mastered through recursive and iterative refinement.
Recursion is the key capability identified in a new theory of linguistic competence. In Noam Chomsky's early
theories of language in humans, he cited many common attributes that account for the similarities in human languages.
In a 2002 paper by Marc Hauser, Noam Chomsky, and Tecumseh Fitch, the authors cite the single attribution of
"recursion" as accounting for the unique language faculty of the human species.
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Recursion is the ability to put
together small parts into a larger chunk, and then use that chunk as a part in yet another structure and to continue this
process iteratively. In this way, we are able to build the elaborate structures of sentences and paragraphs from a limited
set of words.
Another key feature of the human brain is the ability to make predictions, including predictions about the results
of its own decisions and actions. Some scientists believe that prediction is the primary function of the cerebral cortex,
although the cerebellum also plays a major role in the prediction of movement.
Interestingly, we are able to predict or anticipate our own decisions. Work by physiology professor Benjamin
Libet at the University of California at Davis shows that neural activity to initiate an action actually occurs about a
third of a second before the brain has made the decision to take the action. The implication, according to Libet, is that
the decision is really an illusion, that "consciousness is out of the loop." The cognitive scientist and philosopher Daniel
Dennett describes the phenomenon as follows: "The action is originally precipitated in some part of the brain, and off
fly the signals to muscles, pausing en route to tell you, the conscious agent, what is going on (but like all good officials
letting you, the bumbling president, maintain the illusion that you started it all)."
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A related experiment was conducted recently in which neurophysiologists electronically stimulated points in the
brain to induce particular emotional feelings. The subjects immediately came up with a rationale for experiencing
those emotions. It has been known for many years that in patients whose left and right brains are no longer connected,
one side of the brain (usually the more verbal left side) will create elaborate explanations ("confabulations") for
actions initiated by the other side, as if the left side were the public-relations agent for the right side.
The most complex capability of the human brain—what I would regard as its cutting edge—is our emotional
intelligence. Sitting uneasily at the top of our brain's complex and interconnected hierarchy is our ability to perceive
and respond appropriately to emotion, to interact in social situations, to have a moral sense, to get the joke, and to
respond emotionally to art and music, among other high-level functions. Obviously, lower-level functions of
perception and analysis feed into our brain's emotional processing, but we are beginning to understand the regions of
the brain and even to model the specific types of neurons that handle such issues.
These recent insights have been the result of our attempts to understand how human brains differ from those of
other mammals. The answer is that the differences are slight but critical, and they help us discern how the brain
processes emotion and related feelings. One difference is that humans have a larger cortex, reflecting our stronger
capability for planning, decision making, and other forms of analytic thinking. Another key distinguishing feature is
that emotionally charged situations appear to be handled by special cells called spindle cells, which are found only in
humans and some great apes. These neural cells are large, with long neural filaments called apical dendrites that
connect extensive signals from many other brain regions. This type of "deep" interconnectedness, in which certain
neurons provide connections across numerous regions, is a feature that occurs increasingly as we go up the
evolutionary ladder. It is not surprising that the spindle cells, involved as they are in handling emotion and moral
judgment, would have this form of deep interconnectedness, given the complexity of our emotional reactions.
What is startling, however, is how few spindle cells there are in this tiny region: only about 80,000 in the human
brain (about 45,000 in the right hemisphere and 35,000 in the left hemisphere). This disparity appears to account for
the perception that emotional intelligence is the province of the right brain, although the disproportion is modest.
Gorillas have about 16,000 of these cells, bonobos about 2,100, and chimpanzees about 1,800. Other mammals lack
them completely.
Dr. Arthur Craig of the Barrow Neurological Institute in Phoenix has recently provided a description of the
architecture of the spindle cells.
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Inputs from the body (estimated at hundreds of megabits per second), including
nerves from the skin, muscles, organs, and other areas, stream into the upper spinal cord. These carry messages about
touch, temperature, acid levels (for example, lactic acid in muscles), the movement of food through the gastrointestinal
tract, and many other types of information. This data is processed through the brain stem and midbrain. Key cells
called Lamina 1 neurons create a map of the body representing its current state, not unlike the displays used by flight
controllers to track airplanes.
The information then flows through a nut-size region called the posterior ventromedial nucleus (VMpo), which
apparently computes complex reactions to bodily states such as "this tastes terrible," "what a stench," or "that light
touch is stimulating." The increasingly sophisticated information ends up at two regions of the cortex called the insula.
These structures, the size of small fingers, are located on the left and right sides of the cortex. Craig describes the
VMpo and the two insula regions as "a system that represents the material me."
Although the mechanisms are not yet understood, these regions are critical to self-awareness and complicated
emotions. They are also much smaller in other animals. For example, the VMpo is about the size of a grain of sand in
macaque monkeys and even smaller in lower-level animals. These findings are consistent with a growing consensus
that our emotions are closely linked to areas of the brain that contain maps of the body, a view promoted by Dr.
Antonio Damasio at the University of Iowa.
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They are also consistent with the view that a great deal of our thinking
is directed toward our bodies: protecting and enhancing them, as well as attending to their myriad needs and desires.
Very recently yet another level of processing of what started out as sensory information from the body has been
discovered. Data from the two insula regions goes on to a tiny area at the front of the right insula called the
frontoinsular cortex. This is the region containing the spindle cells, and tMRI scans have revealed that it is particularly
active when a person is dealing with high-level emotions such as love, anger, sadness, and sexual desire. Situations
that strongly activate the spindle cells include when a subject looks at her romantic partner or hears her child crying.
Anthropologists believe that spindle cells made their first appearance ten to fifteen million years ago in the as-yet-
undiscovered common ancestor to apes and early hominids (the family of humans) and rapidly increased in numbers
around one hundred thousand years ago. Interestingly, spindle cells do not exist in newborn humans but begin to
appear only at around the age of four months and increase significantly from ages one to three. Children's ability to
deal with moral issues and perceive such higher-level emotions as love develop during this same time period.
The spindle cells gain their power from the deep interconnectedness of their long apical dendrites with many other
brain regions. The high-level emotions that the spindle cells process are affected, thereby, by all of our perceptual and
cognitive regions. It will be difficult, therefore, to reverse engineer the exact methods of the spindle cells until we have
better models of the many other regions to which they connect. However, it is remarkable how few neurons appear to
be exclusively involved with these emotions. We have fifty billion neurons in the cerebellum that deal with skill
formation, billions in the cortex that perform the transformations for perception and rational planning, but only about
eighty thousand spindle cells dealing with high-level emotions. It is important to point out that the spindle cells are not
doing rational problem solving, which is why we don't have rational control over our responses to music or over
falling in love. The rest of the brain is heavily engaged, however, in trying to make sense of our mysterious high-level
emotions.
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