Conservative Left Brain, Liberal Right Brain
Early evidence and relationship to early theories of political orientation
One of the great stories of human behavior may ultimately involve molecular chirality, or the mirror-like structure of chemically identical molecules. Chirality came under public scrutiny in the 1960s, when a drug called thalidomide was prescribed for morning sickness. Thalidomide consists of two chemically identical mirror-image molecules, much like human hands.
The left-handed version of thalidomide was a tranquilizer that quelled the symptoms of nausea. Unfortunately, the right-handed version was not removed during synthesis, and due to its chemical similarity to guanine, would bind into the guanine-rich regions of the DNA molecule, where it would block the proteins that promoted the formation of human limbs. Approximately 10,000 children were born with severe birth defects, including phocomelia, or the attachment of the hands and feet directly to the torso.
Phocomelia highlights the significant impact that molecular chirality has on physiology. But it may also play a very large role in the diversity of human cognition, and ultimately, variation in political and religious attitudes. Recent evidence has implicated cascades of asymmetrically expressed genes, which are initiated by a first embryonic event that distinguishes left from right, and is the start of all subsequent embryonic events that propagate laterality in the developing human embryo. That event, according to the ingenious model of Brown and Wolpert (1990), is the conversion of molecular handedness, or chirality, into handedness at the cellular level.
The final evolutionary result of the chain of events that originated with molecular chirality is this. The left and right brains. This one is of particular interest, in that it is Albert Einstein's brain photographed shortly after his death. And if you look closely, the left and right brains are not exactly symmetrical. This asymmetry is both macro and microscopic, and initiated by the asymmetric expression of genes during the embryogenesis. The left-right dichotomy of the nervous system shows up very early in the animal kingdom, as demonstrated by the asymmetric functionality of chemosensation in nematodes.
In humans, the relationship between asymmetric genetic expression and cerebral lateralization is still poorly understood, but the emerging evidence is implicating a large number of genes. In particular, Walsh (2005) identified 27 genes that are asymmetrically expressed during the embryogenesis of the human left and right cerebral hemispheres.
This hints at the strong evolutionary drive for functional asymmetry in the left and right brains, which seems to have reached its peak in humans. This functional asymmetry seems to increase the processing capacity of an individual brain. More importantly, it also seems to dramatically increase the total processing capacity for a population of humans that communicate with each other.
The functional asymmetry of the human brain has been speculated upon since the ancient Greeks. However, it wasn't until the 19th century, when Marc Dax and Paul Broca noticed that aphasia, or the impairment of the ability to speak, was associated with lesions in the left hemisphere. The lateralization of language processing in the left hemisphere was quite a surprise to the prevailing sentiment that hemispheric function was symmetric.
Toward the end of the 19th century, the evidence was piling up for specialization, with motor control being more prominent in the left hemisphere, while sensory processing seemed more specialized in the right. Further, evidence from stroke victims implicated the right hemisphere to be more emotional than the left. The left hemisphere was not only implicated in controling motor activity on the right side of the body, but also, voluntary actions for the whole body, and looking very much like the source of the "will".
Is the left hemisphere the source of the "Will"?
The seeds of the popular modern-day view of a logical and verbal left hemisphere coupled with a holistic and emotional right hemisphere were becoming quite the rage in France and Germany, but did not translate well to America, which had taken the lead in the science of neuropsychology after World War I. However, neurosurgeons Joseph Bogen and Philip Vogel were treating a group of epileptic patients by the severing the corpus callosum, which was the main communication pathway between the two cerebral hemispheres.
The corpus callosum is the main white-matter bundle in the brain, which consists of roughly 200 million axons connecting the neocortices of the left and right hemispheres. This represents 2-3% of all the axons in the brain, which means that most neural communication actually occurs within the same hemisphere, and not between hemispheres.
The information being relayed across the callosum is both inhibitory and excitatory, targets both homotopic and heterotopic regions, and involves sensory, motor, emotional, and higher cognitive information. The radical treatment of severing the corpus callosum in severe epileptics, originally developed in 1940, was of particular interest to Roger Sperry, who had done numerous experiments involving split-brain cats and monkeys.
Sperry and his group of graduate students, one being Michael Gazzaniga, began a famous series of experiments that would rekindle the popular sentiment of two distinct brains living under the same roof. Indeed, Sperry was a strong proponent of the dual mindedness theory that would become a sub-industry in the lucrative field of pop psychology. Even the popular Myers-Briggs type theory walked down this same pathway, with the perceiving personality trait being associated with the right hemisphere, while the judging personality trait was associated with the left.
What Sperry and his followers revealed was a startling picture of cerebral lateralization, as illustrated by this.
The drawing on the far left, which is a triangle built from tiny squares, was redrawn by patients with either left or right brain damage. The drawing in the middle was done a patient with an intact left hemisphere, while the drawing on the right was done by an intact right hemisphere. The left hemisphere did not see the overall shape of the individual parts. The right hemisphere did not see the individual details within the overall shape. This difference is indicative of two different views of the world, one favoring a sort of categorization system that supports object recognition and relationships (the left hemisphere), and one favoring a sort of spatial mapping system providing a neural analog of the external world (the right hemisphere).
Given that most of the communication in the brain happens within a single hemisphere, and not between the two hemispheres, severing their connection seems to produce two cognitive styles, or a parallax view of the world. But these two worlds often conflict with each other. Let's listen in as Michael Gazzaniga discusses this phenomenon.
Obviously, if the left and right brains could still communicate with each other, this conflict would be fought inside the brain, instead of between the hands. As we shall shortly see, this conflict would be central to two key studies on conservatives and liberals. But this brings us to two split-brain patients of particular political and religious interest. The first is a patient named Paul, that had an enhanced capability for language in his right hemisphere. The Gazzaniga team asked his left and right hemispheres a number of questions, resulting in some interesting discrepancies.
The solid line represents Paul's left hemisphere responses, and the dashed line his right. Paul had five responses to choose from: Like very much (LVM), Like (L), Undecided (U), Dislike (D), and Dislike very much (DVM). As you can see, the two hemispheres mirrored each other's responses fairly well. Paul's right hemisphere liked his father more than his left hemisphere, while liking very much the Happy Days character, the Fonz, God, and Home. Interestingly, the left hemisphere did not like God as much as the right. Both of Pauls hemisphere's liked Paul, himself, to the same degree, while the left hemisphere disliked the police, but was more positive about school and tv.
But the response to the Republican president Richard Nixon had the greatest variance. The left hemisphere liked Nixon, while the right hemisphere disliked him. Not too much can be made of this result, for two reasons. First, a substantial amount of emotional and memory communication is still occuring between the two brains via the anterior commissure, which connects the two amygdalas, and the hippocampal commissure, which connects the hippocampi of both hemispheres. Second, Paul had a unilateral temporal lesion and an enhanced capacity for language in the right hemisphere, which was not the average case.
But another famous split-brain patient, known as LB, had both the anterior and hippocampal commissures severed. In this patient's case, the right and left hemispheres held different views on religion and abortion. The right hemisphere did not believe in God or Christ, but had a moderately strong opinion that there was a soul. Liberals indeed are more likely to consider themselves spiritual than religious. Further, this patient's right hemisphere believed strongly in abortion and justice. While the split-brain evidence has been sparse and subject to multiple interpretations, there are other compelling reasons to believe that the two hemispheres, when separated from each other, diverge politically and religiously.
Let's go back to our previous discussion, in Chapter 1, on two of the earliest theories of conservatism and liberalism: first, Erik Jaensch's perceptual theory. Jaensch believed that the right wingers were perceptually unambiguous, while the left wingers were prone to perceive the world ambiguously. This Nazi theory of political orientation was subsequently echoed by the leftest Else Frenkel-Brunswik, who believed that the right wingers had a tendency towards binary thinking, good and evil, and a disinclination to think in terms of probabilities.
Both Jaensch and Frenkel-Brunswik, like most modern-day theorists of political orientation, assign a sort of psychopathology to the left wing or right wing. Both theories propose a sort of dual mindedness of conservatism and liberalism. But do both of these theories reflect the dual mindedness of the left and right brains?
One of the more curious aspects of political and religious orientation is the correlation between seemingly unconnected traits. That is, why does someone believe strongly in gun control much more like to support abortion rights? Why does someone against the Obama Health Care plan more likely to be in favor of prayer in public schools?
This is a difficult question, but whatever is causing the brain to consistently intermingle political and religious beliefs that have no logical relationship must be pretty be big. As we noted in Chapter 1, political and religious beliefs are closely correlated with Darwinian reproductive strategies. But has the execution of Darwinian reproductive strategy left its mark on the evolution of the left and right hemispheres?
Written and Narrated by Charles Brack, April 2011