Iain McGilchrist: The Master and His Emissary

Our two brain hemispheres are opponent processors:

what does that imply for us and our culture?

Three-dimensional rendering of the inferior surface of the brain, derived from in vivoMRI scanning. There are obvious asymmetries in the anatomy of the two hemispheres - protrusions of the hemispheres, (anteriorly and posteriorly), differences in the widths of the frontal (F) and occipital (O) lobes, and a twisting (torque) effect.

This is a story about ourselves and the world, and about how we got to be where we are now. While much of it is about the structure of the human brain – the place where mind meets matter – ultimately it is an attempt to understand the structure of the world that the brain has in part created. Whatever the relationship between consciousness and the brain – unless the brain plays no role in bringing the world as we experience it into being, a position that must have few adherents – its structure has to be significant. It might even give us clues to understanding the structure of the world it mediates, the world we know. So, to ask a very simple question, why is the brain so clearly and profoundly divided? Why, for that matter, are the two cerebral hemispheres asymmetrical? Do they really differ in any important sense? If so, in what way?

The subject of hemisphere differences has a poor track record, discouraging to those who wish to be sure that they are not going to make fools of themselves in the long run. Views on the matter have gone through a number of phases since it was first noticed in the mid-nineteenth century that the hemispheres were not identical, and that there seemed to be a clear asymmetry of function related to language, favouring the left hemisphere. At first, it was believed that, apart from each hemisphere obviously having sensory and motor responsibility for, and control of, the opposite (or ‘contra-lateral’) side of the body, language was the defining difference, the main specific task of the left hemisphere. The right hemisphere was considered to be essentially ‘silent’. Then it was discovered that, after all, the right hemisphere appeared better equipped than the left hemisphere to handle visual imagery, and this was accepted as the particular contribution it made, its equivalent to language: words in the left hemisphere, pictures in the right. But that, too, proved unsatisfactory. Both hemispheres, it is now clear, can deal with either kind of material, words or images, in different ways.

This is hardly surprising, given the set of beliefs about the differences between the hemispheres which has passed into the popular consciousness. These beliefs could, without much violence to the facts, be characterised as versions of the idea that the left hemisphere is somehow gritty, rational, realistic but dull, and the right hemisphere airy-fairy and impressionistic, but creative and exciting. In reality, both hemispheres are crucially involved in reason, just as they are in language; both hemispheres play their part in creativity. Perhaps the most absurd of these popular misconceptions is that the left hemisphere, hard-nosed and logical, is somehow male, and the right hemisphere, dreamy and sensitive, is somehow female... Discouraged by this kind of popular travesty, neuroscience has returned to the necessary and unimpeachable business of amassing findings, and has largely given up the attempt to make sense of the findings, once amassed, in any larger context.

Nonetheless it does not seem to me likely that the ways in which the hemispheres differ are simply random, dictated by purely contingent factors such as the need for space, or the utility of dividing labour, implying that it would work just as well if the various specific brain activities were swapped around between hemispheres as room dictates. Fortunately, I am not alone in this. Despite the recognition that the idea has been hijacked by everyone from management trainers to advertising copywriters, a number of the most knowledgeable people in the field have been unable to escape the conclusion that there is something profound here that requires explanation. Joseph Hellige, for example, arguably the world’s best informed authority on the subject, writes that while both hemispheres seem to be involved in one way or another in almost everything we do, there are some ‘very striking’ differences in the information-processing abilities and propensities of the hemispheres. V. S. Ramachandran, another highly regarded neuroscientist, accepts that the issue of hemisphere difference has been traduced, but concludes: ‘The existence of such a pop culture shouldn’t cloud the main issue – the notion that the two hemispheres may indeed be specialised for different functions.’  And recently Tim Crow, one of the subtlest and most sceptical of neuroscientists researching into mind and brain, who has often remarked on the association between the development of language, functional brain asymmetry and psychosis, has gone so far as to write that ‘except in the light of lateralisation, nothing in human psychology/psychiatry makes any sense.’ There is little doubt that the issues of brain asymmetry and hemisphere specialisation are significant. The question is only – of what?

I believe there is, literally, a world of difference between the hemispheres. Understanding quite what that is has involved a journey through many apparently unrelated areas: not just neurology and psychology, but philosophy, literature and the arts, and even, to some extent, archaeology and anthropology, and I hope the specialists in these areas will forgive my trespasses. Every realm of academic endeavour is now subject to an explosion of information that renders those few who can still truly call themselves experts, experts on less and less. Partly for this very reason it nonetheless seems to me worthwhile to try to make links outside and across the boundaries of the disciplines, even though the price may be that one is always at best an interested outsider, at worst an interloper condemned to make mistakes that will be obvious to those who really know. Knowledge moves on, and even at any one time is far from certain. My hope is only that what I have to say may resonate with the ideas of others and possibly act as a stimulus to further reflection by those better qualified than myself.

I have come to believe that the cerebral hemispheres differ in ways that have meaning. There is a plethora of well-substantiated findings that indicate that there are consistent differences – neuropsychological, anatomical, physiological and chemical, amongst others – between the hemispheres. But when I talk of ‘meaning’, it is not just that I believe there to be a coherent pattern to these differences. That is a necessary first step. I would go further, however, and suggest that such a coherent pattern of differences helps to explain aspects of human experience, and therefore means something in terms of our lives, and even helps explain the trajectory of our common lives in the Western world.

My thesis is that for us as human beings there are two fundamentally opposed realities, two different modes of experience; that each is of ultimate importance in bringing about the recognisably human world; and that their difference is rooted in the bi-hemispheric structure of the brain. It follows that the hemispheres need to co-operate, but I believe they are in fact involved in a sort of power struggle, and that this explains many aspects of contemporary Western culture.

[Introduction, pp1-3]

Essential Asymmetry

‘The universe is built on a plan, the profound symmetry of which is somehow present in the inner structure of our intellect.’ This remark of the French poet Paul Valéry is at one and the same time a brilliant insight into the nature of reality, and about as wrong as it is possible to be.

In fact the universe has no ‘profound symmetry’ – rather, a profound asymmetry. More than a century ago Louis Pasteur wrote: ‘Life as manifested to us is a function of the asymmetry of the universe . . . I can even imagine that all living species are primordially, in their structure, in their external forms, functions of cosmic asymmetry.’ Since then physicists have deduced that asymmetry must have been a condition of the origin of the universe: it was the discrepancy between the amounts of matter and antimatter that enabled the material universe to come into existence at all, and for there to be something rather than nothing. Such unidirectional processes as time and entropy are perhaps examples of that fundamental asymmetry in the world we inhabit. And, whatever Valéry may have thought, the inner structure of our intellect is without doubt asymmetrical in a sense that has enormous significance for us.

As I have said, I believe that there are two fundamentally opposed realities rooted in the bi-hemispheric structure of the brain. But the relationship between them is no more symmetrical than that of the chambers of the heart – in fact, less so; more like that of the artist to the critic, or a king to his counsellor.

There is a story in Nietzsche that goes something like this. There was once a wise spiritual master, who was the ruler of a small but prosperous domain, and who was known for his selfless devotion to his people. As his people flourished and grew in number, the bounds of this small domain spread; and with it the need to trust implicitly the emissaries he sent to ensure the safety of its ever more distant parts. It was not just that it was impossible for him personally to order all that needed to be dealt with: as he wisely saw, he needed to keep his distance from, and remain ignorant of, such concerns. And so he nurtured and trained carefully his emissaries, in order that they could be trusted. Eventually, however, his cleverest and most ambitious vizier, the one he most trusted to do his work, began to see himself as the master, and used his position to advance his own wealth and influence. He saw his master’s temperance and forbearance as weakness, not wisdom, and on his missions on the master’s behalf, adopted his mantle as his own – the emissary became contemptuous of his master. And so it came about that the master was usurped, the people were duped, the domain became a tyranny; and eventually it collapsed in ruins.

The meaning of this story is as old as humanity, and resonates far from the sphere of political history. I believe, in fact, that it helps us understand something taking place inside ourselves, inside our very brains, and played out in the cultural history of the West, particularly over the last 500 years or so. I hold that, like the Master and his emissary in the story, though the cerebral hemispheres should co-operate, they have for some time been in a state of conflict. The subsequent battles between them are recorded in the history of philosophy, and played out in the seismic shifts that characterise the history of Western culture. At present the domain – our civilisation – finds itself in the hands of the vizier, who, however gifted, is effectively an ambitious regional bureaucrat with his own interests at heart. Meanwhile the Master, the one whose wisdom gave the people peace and security, is led away in chains. The Master is betrayed by his emissary.  

[Into., pp13-14]

The above was extracted from The Master & his Emissary -The Divided Brain & the Making of the Western World.  Nominating it as Observer Book of the Year,  Salley Vickers called it "a monumental account of right and left brain hemispheres...both brilliant & disturbing."

Evaluation of the Left-Brain vs. Right-Brain Hypothesis

An Evaluation of the Left-Brain vs. Right-Brain Hypothesis with Resting State Functional Connectivity Magnetic Resonance Imaging

Jared A. Nielsen , Brandon A. Zielinski, Michael A. Ferguson, Janet E. Lainhart, Jeffrey S. Anderson

Published: August 14, 2013. DOI: 10.1371/journal.pone.0071275. Featured in PLOS Collections

Abstract

Lateralized brain regions subserve functions such as language and visuospatial processing. It has been conjectured that individuals may be left-brain dominant or right-brain dominant based on personality and cognitive style, but neuroimaging data has not provided clear evidence whether such phenotypic differences in the strength of left-dominant or right-dominant networks exist. We evaluated whether strongly lateralized connections covaried within the same individuals. Data were analyzed from publicly available resting state scans for 1011 individuals between the ages of 7 and 29. For each subject, functional lateralization was measured for each pair of 7266 regions covering the gray matter at 5-mm resolution as a difference in correlation before and after inverting images across the midsagittal plane. The difference in gray matter density between homotopic coordinates was used as a regressor to reduce the effect of structural asymmetries on functional lateralization. Nine left- and 11 right-lateralized hubs were identified as peaks in the degree map from the graph of significantly lateralized connections. The left-lateralized hubs included regions from the default mode network (medial prefrontal cortex, posterior cingulate cortex, and temporoparietal junction) and language regions (e.g., Broca Area and Wernicke Area), whereas the right-lateralized hubs included regions from the attention control network (e.g., lateral intraparietal sulcus, anterior insula, area MT, and frontal eye fields). Left- and right-lateralized hubs formed two separable networks of mutually lateralized regions. Connections involving only left- or only right-lateralized hubs showed positive correlation across subjects, but only for connections sharing a node. Lateralization of brain connections appears to be a local rather than global property of brain networks, and our data are not consistent with a whole-brain phenotype of greater “left-brained” or greater “right-brained” network strength across individuals. Small increases in lateralization with age were seen, but no differences in gender were observed.

Neuromyth 6: The left brain/ right brain

The left brain/ right brain myth

Are you a creative and emotional person? Maybe an artist or a musician? Then you are probably right-brained. No? Perhaps you are a rational, analytical and logical thinker? Maybe a mathematician or an engineer? Then you are most likely left-brained. Who does not know that creativity and emotion are located in the right half of the brain, while rationality and logic are situated in the left half of the brain? Everyone has come across this popular notion of left or right brain dominance, which determines a person's way of thinking and his/her personality. This notion, however, is a widely held misconception. Here we will discuss the concept of this notion, known as hemisphericity or hemispheric dominance, how it arose, and why it is a misconception.

Two parts of the brain: two ways of thinking? Two different kinds of personality?

The concept of hemispheric dominance ascribes different information processing characteristics of to one or the other of the two brain hemispheres (see Table 1). It is concluded, therefore, that the dominant use of either the left or the right hemisphere determines a person's way of thinking and personality.

According to the ascribed characteristics, the left brain is the rational, intellectual, logical, analytical and verbal hemisphere. It is the hemisphere that specialises in processing verbal and numerical information in a deductive or logical way. It is the hemisphere that specialises in processing verbal and numerical information based on a deductive or logical way of thinking. This means the left hemisphere dissects information by analysing and distinguishing the single parts of the whole. Thereby it processes the information sequentially in a linear and ordered manner.

Thus, it is asserted that the left hemisphere has a bias for detailed information, is very capable of analysing and structuring information, and is best suited for tasks that comprise language, reading and writing, algebra, mathematical problems, logic operations, and the processing of serial sequences of information. Based on these thinking and problem solving attributes of the left hemisphere, the concept of hemispheric dominance asserts that people who predominantly use the left part of their brain are rational, intellectual, detail oriented, logical and analytical. That means that these people do well in tasks that require these abilities, such as mathematics, engineering or natural sciences.

In contrast to the left brain's analytical way of thinking, the right brain has attributed to it an intuitive, emotional, holistic, synthesising, non-verbal, visuo-spatial mode of processing, resulting in a creative or inductive way of thinking. Thus, the right hemisphere lumps together information and processes it as a whole and in parallel, i.e. it sees the forest rather than the trees. It is supposed to deal in three-dimensional forms and images with a focus on similarities rather than differences, and so is seen as being strong in tasks that require the understanding of complex configurations and patterns and the simultaneous processing of diverse information like pattern recognition, face recognition or spatial relationships. Due to these characteristics, people who predominantly use their right brain are considered as being artistic, intuitive, emotional, imaginative and visually oriented. These people are strong in tasks that require synthesising and conceptualising abilities and hence are said to be good at gathering, assembling, comparing and reshuffling ideas in order to come up with new concepts. Furthermore, it is asserted that they have a strongly developed emotional and aesthetic sensitivity and often follow creative and artistic professions.

Table 1. Postulated characteristics of the two halves of the brain

Left hemisphere	Right hemisphere
Verbal	Non-verbal, Visuo-spatial
Sequential	Simultaneous
Logical	Holistic
Analytical	Synthesising, Integrating
Rational, Intellectual	Intuitive, Emotional

The concept of hemisphericity in learning and education

According to the concept of hemisphericity, information is processed in different ways in the two brain hemispheres. It further states that the dominant brain hemisphere determines the way of processing. On the basis of this notion, the idea developed that the learning and thinking process could be enhanced when both sides of the brain participated in a balanced manner. Consequently, teaching and education programs were developed in order to strengthen the less dominant hemisphere of the brain and to synchronise the two hemispheres. Since it is assumed that schools generally favour left-brained ways of thinking and learning, such as analysis, logic and accuracy, many teaching instruction techniques seek to include more right-brained activities. One example of such a whole-brained instruction method is "show and tell": instead of only reading a "left-brained" text, the teacher also shows pictures and graphics in order to activate the right hemisphere. Other methods include the use of music, metaphors, role plays, meditation, drawing, etc. in order to achieve the synchronisation of the two hemispheres. A general outline of the teaching and problem solving styles of the two hemispheres is given in Table 2. While such methods could be valuable in the educational setting, they are based on a shaky foundation. The reduction of the two sides of the brain to mere seats of certain skills or qualities and the application of this to education, are based on oversimplifications of tendencies that the brain exhibits. These will be more thoroughly explained under the following point.

Table 2. Problem solving skills and related teaching styles incorrectly attributed to the two brain hemispheres

Left brain	Right brain
Rational Looks at differences Solves problems by logically and sequentially looking at the parts of things planned and structured	Emotional, intuitive Looks at similarities Solves problems with hunches, by looking for patterns and configurations fluid and spontaneous
Teaching style verbal instructions talking and writing multiple choice tests	Teaching style demonstrated instructions drawing and manipulating objects Prefers open ended questions

The origin of hemisphericity

Throughout history, the intellectual skills of humans were often divided up into two classes: critical and analytic skills as opposed to creative and synthesising skills. This idea was attributed to the two brain hemispheres and became a major doctrine in neurophysiology in the 19th century. In 1844, Arthur Ladbroke Wigan published a book entitled "A New View of Insanity: Duality of the Mind". In this book, he describes the two brain hemispheres as independent parts having an independent will and way of thinking. Usually they work together, but in the case of a disease, for example, they might work against each other. This notion became very popular and even found its way into popular culture as with Robert Louis Stevenson's famous story "The strange case of Dr. Jekyll and Mr. Hyde" (1886), which explores the idea of a cultured left hemisphere in contrast to an emotional right hemisphere, that is primitive and easily out of control.

Language lateralisation and hemispheric dominance of the left hemisphere

Pierre Paul Broca, a French neurologist, was the first to come up with empirical evidence supporting the localisation of different functions in the two hemispheres. Between 1861 and 1863, Broca examined the brains of more than 20 patients with compromised language function after they had died. In all patients, he found there was damage to the left frontal hemisphere, while the right hemisphere was undamaged. He concluded from his observations that speech production is localised in the frontal part of the left brain hemisphere. A few years later, Wernicke, a German neurologist, extended Broca's view of language localisation. Like Broca, he examined the brains of individuals who had language development impairments. Based on these post-mortem correlations, Wernicke suggested that the ability to comprehend language is located in the temporal lobe of the left hemisphere. Broca and Wernicke both ascribed the comprehension and the production of language, the major determinants of language, to the left hemisphere.

Until the 1960s, observations about language lateralisation were primarily based on post-mortem studies of patients with brain damage of variable location, severity and aetiology. Critics argued that language function might not be lateralised at all. However, definite evidence for language lateralisation arose from studies in split brain patients. In these patients, the nerve fibres that connect the two hemispheres were severed in order to stop the spread of epileptic seizures from one hemisphere to the other. As a result, investigators could study the function of each half of the brain in isolation from the other. The pioneering studies of these split brain patients were carried out in the 1960s and 1970s by the Nobel Prize laureate Roger Sperry and his colleagues at the Californian Institute of Technology. These provided further experimental evidence on hemispheric specialisation in terms of language lateralisation and the localisation of other skills. In order to assess possible functional differences, Roger Sperry and his colleagues provided information only to one side of the brain in split brain patients, such as asking the patients to use each hand independently for the identification of objects without looking at the object.

To understand this procedure, it is important to know that the basic sensory and motor functions are symmetrically divided between the two brain hemispheres: the left hemisphere processes information for the right half of the body and vice versa. Thus, the right hand provides the left hemisphere with information about what it feels. Sperry's experiments yielded an amazing result: when split brain patients processed an object with their right hand, i.e. with their left hemisphere, they could easily name the object. In contrast, when an object was touched with the left hand, i.e. processed by the right hemisphere, they could not name it! This finding put an end to the century long discussion on language lateralisation. It affirmed that the left hemisphere is unequivocally the seat of the major language functions in most individuals.

This unequal representation of language functions in the two hemispheres gave rise to the idea that the left hemisphere is the verbal one, while the right hemisphere is the non-verbal one (see Table 1). Since language has often been regarded as the highest cognitive human achievement, the finding of the hemispheric lateralisation of language further laid the foundation for the misleading concept that one brain hemisphere is "dominant" over the other; namely the left hemisphere, which is the seat of the major capacity for language. In 1868, John Hughlings Jackson, a British neurologist, described this concept of a dominant hemisphere as follows: "Both brains cannot only be duplicates, if damage to only one hemisphere leaves a person speechless. For the processes of language, which are the highest processes possible, there must be one leading side. And in most people, the left brain hemisphere – the side of the will – is the leading one, while the right hemisphere is the automatic one."

Visuo-spatial and emotional preponderance of the right hemisphere

Other experiments with split brain patients investigated the role of the right hemisphere. The results of these experiments were that the right hemisphere is specialised in processing complex visual and spatial conditions. A video by Sperry and Gazzaniga about the split-brain patient W.J. shows one of the most impressive demonstrations of the superiority of the right hemisphere for visuo-spatial tasks: the patient was given several dice, each with two red sides, two white sides and two sides diagonally separated into white and red stripes. The task of the patient was to arrange the dice according to patterns presented on cards. The beginning of the video shows that W.J. quickly arranges the dice in the required pattern using his left hand (right hemisphere). However, he has great difficulty completing the same task using his right hand. He is slowly and indecisively moving the dice around, when his left hand starts to help and quickly starts to arrange the dice correctly. The investigator draws W.J's left hand slowly away and again W.J. is lost using only his right hand, moving the dice around unsystematically. This video, as well as other studies by Roger Sperry, clearly show the preponderance of the right hemisphere in processing visuo-spatial stimuli. This role of the right hemisphere is further corroborated with clinical case studies. Patients with certain damage to the right hemisphere are unable to recognise familiar faces (prosopagnosia). Other patients with right hemispheric damage have difficulties in spatial orientation.

Furthermore, clinical studies let researchers postulate that the right hemisphere is specialised in emotion processing. Emotional expression, as well as emotional recognition and discrimination, are impaired after lesions to the right brain hemisphere: patients with right hemispheric lesions show deficits in identifying the emotional intonation (prosody) of words. In addition, deficits in recognition of emotional facial expression have been linked to lesions of the right hemisphere. These clinical findings are supported by behavioural studies: prosody (emotional speech characteristics) is more easily recognised when stimuli are presented to the left ear (right hemisphere). Furthermore, stimuli presented to the left visual field (right hemisphere) are judged to be more emotional and even to elicit stronger responses from the autonomic nervous system.

Sequential and simultaneous processing in the two hemispheres

By now, we know upon which findings the characteristic "verbal for the left hemisphere, and non-verbal, but visuo-spatial and emotional for the right hemisphere" are based. The next characteristic differences of the hemispheres listed in Table 1 concern sequential (serial) processing of the left hemisphere and simultaneous (parallel) processing of the right hemisphere. This idea reflects the widespread – but not generally accepted – model, which says that the left hemisphere preferentially processes fast changes and analyses details and characteristics of stimuli, while the right hemisphere deals with the simultaneous and global characteristics of stimuli. The other hemispheric characteristics in Table 1 (analytical, rational vs. holistic, intuitive) are not very well supported by scientific evidence, and remain rather speculative. Starting from the difference between verbal and non-verbal, more and more abstract concepts and relations between mental functions and the hemispheres were developed. During this process, the ideas about the difference of the two hemispheres departed more and more from the basic scientific results.

The two hemispheres and their ways of thinking

Some researchers interpreted the specialised functions of the two hemispheres as different thinking styles. Thus, the localisation of language and the proposed serial processing of stimuli in the left hemisphere were equated with a rational, analytical, logical thinking style, while the preponderance in the right hemisphere of non-verbal, visuo-spatial tasks, together with the proposed simultaneous processing, was equated with a holistic, intuitive, emotional way of thinking. In 1970, in his influential book "The Psychology of Consciousness", the psychologist Robert Ornstein hypothesised that Western people only use half their brains and hence only half their mental capacity. He argued that people in Western cultures have a well trained left hemisphere, due to the focus on language and logical thinking. They do, however, neglect their right hemisphere and its intuitive, emotional way of thinking. In short, Ornstein equated the left hemisphere with an analytical, logic way of Western thinking, and the right hemisphere with an intuitive, emotional Eastern way of thinking. Thus the traditionally established dualism of intellect and intuition got a physiological foundation based on the differences of the two brain hemispheres.

This view resulted in many misinterpretations and incorrect assertions, which were far from the scientific findings. Facts and conjecture became blurred and the two hemispheres of the brain were not only ascribed two different thinking styles, but also two different personality styles. The concept of right brain and left brain thinking, together with the idea of a dominant hemisphere, resulted in the notion that people rely predominantly on one or the other way of thinking, i.e. they rely on either the left or the right hemisphere. It has been supposed that this usage of one or the other half of the brain is reflected in the cognitive style of an individual: a person, who thinks rationally and analytically was said to be left hemispheric. In contrast, a person who processes information intuitively and emotionally was classified as right hemispheric. The hemispheric ways of thinking and of cognitive style became very popular and can nowadays be found in a variety of periodicals, workshops and self-help books. They even found their application in the field of education.

Hemispheric thinking and personality styles in learning and education

The concepts of right brain and left brain thinking and personality styles have raised many questions with regard to their application in education. Which learning and teaching styles consider the individual use of the hemispheres best? How should curricula be designed to guarantee whole-brained learning? Is our educational system too left-brained, with its focus on language and mathematics? How could right-brained skills be developed?

Joseph Bogen, one of the pioneers in split brain surgery, as well as the psychologist Robert Ornstein (see above), stated that our societies focus on a thinking style that uses statements (language) for information processing, i.e. the left hemispheric way of thinking. In contrast, they stated that our societies neglect right hemispheric thinking styles, such as creativity. The notion that our societies, including our education system, focus on only half of our mental capacities, i.e. the left hemispheric way of thinking, and neglects the other half, the right hemispheric way of thinking, became more and more widespread.

Well-known educationalists, such as E.P. Torrance or Madeline Hunter, recommended that schools change the existing teaching methods and assessment procedures according to the concept of hemisphericity. Hunter stated that school curricula are predominantly aimed at left-brain learners. E.P. Torrance argued that schools favour left-brained activities, such as sitting erect or learning algebra, while right hemispheric functioning should include activities such as lying down or learning geometry. Others also supported the notion of a dominance of left brain functioning in education, arguing that the educational agenda of most schools revolves around left-brained subjects, such as language and mathematics. As a consequence, many whole-brained learning and teaching methods evolved. While these methods could be valuable in the educational setting, they are based on a shaky foundation. As we have seen, there is only some experimental support for the concept of hemisphericity. In addition, subsequent research has shown that things are neither quite as polarised as once thought, nor as simple. The application of this notion to educational practice seems, therefore, overly simplistic and even dubious.

Arguments against hemisphericity

Arguments against a left brain and right brain thinking style and its application to education

The notion of different hemispheric thinking styles is based on an erroneous premise: each brain hemisphere is specialised and therefore each must function independently with a different thinking style. This connection is a bridge too far: it uses scientific findings regarding functional asymmetries for the processing of stimuli to create conceptions about hemispheric differences on a different level, such as a cognitive thinking style. Furthermore, there is no direct scientific evidence supporting the idea that different thinking styles lie within each hemisphere. Indeed, deriving different hemispheric thinking styles from functional asymmetries is quite a bold venture, which oversimplifies and misinterprets scientific findings.

If one considers the right hemispheric creative and emotional thinking style, there is no scientific evidence that supports a correlation between creativity and the activity of the right hemisphere, let alone evidence for a correlation between the degree of creativity and the use of the right hemisphere. Similarly, a recent analysis of 65 neuroimaging studies on emotion found no scientific support for the hypothesis of an overall right hemispheric lateralisation of emotional function. There is no direct scientific evidence that supports an analytical, logical thinking style for the left hemisphere, which predetermines the left hemisphere for mathematical tasks, or reading and writing. In contrast, Stanislas Daheane found that both the right and left hemisphere are active in the identification of Arabic numerals (e.g. "1","2"). Similarly, other data showed that subsystems in both hemispheres are activated for parts of the reading process, e.g. decoding written words or recognising speech sounds. Based on these and many more scientific findings, scientists nowadays think that while there are some functional asymmetries, the two brain hemispheres do not work in isolation, but rather together in every cognitive task. In light of this notion, using the conception of hemisphericity to guide and direct educational practice is highly questionable.

References

Understanding the Brain: Towards a New Learning Science, OECD 2002, Chapter 4.6 pp.69-77.

Springer S.P. and Deutsch, G. (1998). Left brain, right brain. New York: W.H. Freeman.

Wagner T.D., Phan L.K., Liberzon, I., Taylor S.F. (2003) Valence, gender, and lateralization of functional brain anatomy in emotion: a meta-analysis of findings from neuroimaging. NeuroImage 19, 513-531

Zalewski L. J., Sink C. A., Yachimowicz D.J. (1992) Using Cerebral Dominance for Educational Programs. The Journal of General Psychology 119 (1), 45-57

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RSA Animate - The Divided Brain

In this new RSA Animate, renowned psychiatrist and writer Iain
McGilchrist explains how our 'divided brain' has profoundly altered
human behaviour, culture and society.

The Master and His Emissary (review)

By Jim Coughenour on February 21, 2010

Format: Hardcover

Ian McGilchrist's thick book on the "divided brain" is the most interesting book I've read this year. I'd come to regard the fabled right brain/left brain antithesis as so much entertaining pop psychology (e.g., Daniel Pink's A Whole New Mind: Why Right-Brainers Will Rule the Future) -- handy for provoking corporate robots, but hardly more than a convenient fiction. McGilchrist has convinced me that it's a metaphor worth taking seriously, that in fact it may be the fundamental metaphor for a scientistic age.

McGilchrist's thesis is simple: the right hemisphere of the brain (the "Master" of his title) provides our primary connection to the world - to whatever is outside ourselves; the left hemisphere is its Emissary, breaking wholes into parts, analyzing and abstracting, devising categories, names and theories, then returning the results of its investigations to the right brain to be integrated into lived experience. The health of both individuals and civilizations depends upon the reciprocal connection. The problem is that the left brain, which imagines it "knows" things it can't possibly know, usurps its role and projects its own partial, definite vision of the world onto the world's essentially ambiguous reality.

Stated simply (and the above is my own wording for McGilchrist's argument) I risk making the book sound as if it was written by a crank with an overweening metaphor. Nothing could be further from the truth. The book, which begins by examining a huge range of neurological research on the brain, then examines how the structure of the brain has affected (nothing less than!) the history of Western civilization, is continuously fascinating, rich in detail and bold in observation. Bothits science and practice of philosophy are exemplary. McGilchrist takes almost 500 pages to build his case. Fortunately, he's an engaging and unpretentious writer.

His argument reminded me of some of the most stimulating books I've ever read. A short list of ideational echoes: James Hillman's discussion of "seeing through" in Re-Visioning Psychology; Owen Barfield's examination of polarity in the evolution of consciousness in What Coleridge Thought; F S C Northrup's study of the Aesthetic and Theoretic components in The Meeting of East and West; Paul Ricoeur's theory of "second naivete" in The Symbolism of Evil; and Colin Falck's post-structuralist approach to literary language in Myth, Truth and Literature: Towards a True Post-modernism . Each of these books is a touchstone to me, and each is illuminated by McGilchrist's speculations.

At the same time, McGilchrist's discussion and bibliography pointed me to books I'd never heard of and now can't wait to read: Louis Sass's Madness and Modernism: Insanity in the Light of Modern Art, Literature, and Thought; Stephen Gaukroger's The Emergence of a Scientific Culture: Science and the Shaping of Modernity 1210-1685; and Joseph Leo Koerner's The Reformation of the Image. I realize this review doesn't do much more than emphasize my own enthusiasm - but for the curious reader, maybe that will suffice.

A Crash Course on Gender Differences

On Men Women and Evolution- Testing the Myth

Post published by Eyal Winter on May 09, 2015 in Feeling Smart

Session 1

Love and sexuality are far and away the most important emotional phenomena for our direct genetic survival. It is no surprise that nearly 80 percent of people surveyed by Daniel Kahneman and his colleagues in the course of their research on happiness reported that sexuality and love are the most decisive factors in their lives for achieving happiness.1 The other rational emotions are important for evolutionary survival because they increase our fitness to our environment and our personal chances for survival. But love and sexuality directly contribute to our genetic survival by enabling us to reproduce and raise offspring.

Love is not a mechanism that is needed for reproduction in most animals, for whom sexual relations alone suffice. These typically involve brief sexual encounters, often only once with each mate, with males taking on little or no responsibility for caring for their offspring.

Many of us may also know humans who fit this description in their attitudes toward sexual relations. But most of humanity exhibits a different pattern of sexual behavior. The institution of marriage, a nearly universal cultural phenomenon, is a strong expression of the more typical human attitude toward love and sexuality. This distinction between human sexuality and that of most animals is related to the fact that raising a human child is a very long and complex process requiring the involvement of more than one parent.

While humans wait patiently for up to a full year or more for infants to learn to walk after their births, newborn gazelles are up and walking within two days of their births. Equine mares watch their newborn foals take their first steps within half a day of birth.

The life expectancy of gazelles and horses is shorter than that of human beings, but it still ranges up to about thirty years. Raising a human child to the point of complete independence from adult care and supervision takes about 20 percent of modern human life expectancy. Until about two hundred years ago, it required as much as 30 percent of life expectancy. There are virtually no other animals that go through such a lengthy juvenile period relative to their life expectancies.

From the evolutionary perspective there is no point in having offspring unless those offspring in turn have offspring of their own. Only a child who has reached independent adulthood can contribute to the genetic survival of his or her parents. If childhood were sufficiently short relative to the life span of a single parent, and demanded relatively few resources, mothers could reasonably care for their offspring on their own. The longer childhood lasts and the more one needs to invest resources in raising a child, the more important it becomes for the father, who also benefits (genetically) from having offspring who successfully reach adulthood, to share in the burden of raising the child.

In my book "Feeling Smart: Why our Emotions are More Rational than We Think" I look into the roles that social emotions play in creating commitment. Anger, for example, helps us create credible threats. Love, in contrast, creates credible commitment for altruistic behavior toward mates, a commitment that is a precondition for parental cooperation in caring for offspring. From the male perspective, the commitment arising from love within a couple increases the chances that the child he is helping to raise is indeed his child, carrying genes that are similar to his, and not the child of another man with whom his spouse has had relations. Love and social structures that are built on stable monogamous relationships are the result of the large amount of parental energy humans need to invest for the successful survival of their offspring.

Human parents generally care simultaneously for children who were born in different pregnancies. This is not a phenomenon that characterizes other animals, whose offspring leave their parental nests before their mothers reproduce again. My colleague Motty Perry coauthored an excellent paper that used game theory to show that this phenomenon is responsible for the familiar structure of the human family, in addition to the commitments that members of couples exhibit toward each other.2 Without these commitments, men would never know if the food that they have worked so hard to obtain and give to their spouses will be passed on to feed their children as opposed to the children of other men from previous pregnancies.

Human childhood is very lengthy because human children need to learn complex social skills, over and above the physical and cognitive growth that all animals undergo as juveniles. Very few animals form long-term stable couplings with a single mate (hamsters and foxes are two noteworthy exceptions). The vast majority of animals have what we humans might call far more "steamy sex lives," based on casual sexual encounters. The sole purpose of their sexual interactions is procreation. Sexuality in these species is based on intense and sometimes violent "sperm competition" between males, along with selective female receptivity to the mating efforts of the males, with only the males deemed most fit on the part of the females succeeding in mating.

(Next week: Strategies in "Sperm Competition")

Session 2

Last week we mentioned:

1. This distinction between human sexuality and that of most animals is related to the fact that raising a human child is a very long and complex process requiring the involvement of more than one parent.

2. Sexuality most species is based on intense and sometimes violent "sperm competition" between males, along with selective female receptivity to the mating efforts of the males, with only the males deemed most fit on the part of the females succeeding in mating.

We now continue:

The specific characteristics of sperm competition between males vary from one species to another, depending on evolutionary developments. Competition between drones (male bees), for example, comes down to a total of about ten minutes out of their very brief lives. When a virgin queen bee is ready to mate, she enters a vigorous dancing state, drawing a swarm of drones. Only the strongest and quickest drones can succeed in mounting the larger queen bee and inserting their sperm into her. The drones die shortly afterward, while the queen bee stores their sperm for the rest of her life (up to thirty years) for use in fertilizing the millions of ova she produces.

Sperm competition between male mice is no less interesting. Its main expression comes after the act of mating has been completed. After inserting his sperm into a receptive female, the male secretes a sticky substance that essentially blocks the female's reproductive tract to prevent other males from successfully mating with her until his sperm has been fully absorbed inside the female. This strategy, reminiscent of the chastity belts that the knights of the Middle Ages once locked their wives in before going out to battle, increases the male's chances of successfully fertilizing a female with whom he mates and also incentivizes him to care for her offspring because he has greater certainty that her offspring are his.

Sperm competition strategies vary widely between species, but generally it is one of two kinds of evolutionary strategies for ensuring the survival of one's DNA. The other is a "marketing strategy" (think of the peacock's tail and other characteristics and behaviors that can be explained using the handicap principle) used to increase the attractiveness of individual males in the eyes of females.

Men and women have evolved differences in their emotional and sexual behavior due to physiological differences related to reproduction between the two sexes. Reproductive asymmetries between men and women are expressed in three main ways:

1. The maximal number of children that a woman can bear in a lifetime is well below one hundred (the best documented historical record of the greatest number of children borne by one woman is held by a Russian peasant woman who lived in the eighteenth century and gave birth to sixty-four children through twenty-seven pregnancies). In contrast, a man can theoretically father 100,000 children. Similarly, while a woman can reach her maximal reproductive potential by mating with only one man throughout her life, a man would need about a thousand women to attain his maximal reproductive potential.

2. A woman knows with exact certainty who her biological children are: the children emerging from her womb. A man can never be certain whether the children borne by his spouse are indeed his biological children.

3. In the reproductive process itself mothers invest far more resources than fathers because mothers carry fetuses within them for nine months of pregnancy.

In addition to these three differences, men and women differ in one more relevant physiological actor: men on average have greater muscle mass than women.

To get an idea of the extent to which these physical and physiological distinctions influence differences in emotional reactions and sexual behaviors between men and women, I will review several widespread clichés, taking a close look at each one. Keep in mind that the evolutionary forces that have been shaping differences between the sexes long predate the feminist revolution and the modern era. They existed before human civilization arose, under conditions of a daily struggle for survival in which lack of close care for a child on the part of both parents meant almost certain death for the child.

To be continued next week same time with testing of varoius cliche's on gender differences. Stay tuned!

Session 3

Last week we discussed the reproductive asymmetries between men and women. We mentioned that they are expressed in three main ways:

1. The maximal number of children that a woman can bear in a lifetime is well below one hundred, while, a man can theoretically father 100,000 children.

2. A woman knows with exact certainty who her biological children are: the children emerging from her womb. A man can never be certain whether the children borne by his spouse are indeed his biological children.

3. In the reproductive process itself mothers invest far more resources than fathers because mothers carry fetuses within them for nine months of pregnancy.

We shall now examine several widely spread clichés on gender differences:

Cliché 1: Men are far more likely than women to agree to brief one-time sexual encounters without emotional commitments.

The facts: A man can theoretically father a thousand times as many children as any one woman can bear. In practice, men and women have the same number of children on average for the simple reason that each child has precisely two biological parents. This brings about a situation in which men are in perpetual competition with other men in the race for greater fertility. From this perspective, a long-term commitment to one partner reduces a man's genetic survival potential because it limits the number of children he can have to the upper limit of children that his partner can bear for him. In contrast, women need only one man to attain their maximal fertility, and gain no advantage in having multiple sexual partners.

Cliché 2: Women have a greater need than men to express love.

The facts: As noted above, having sexual relations with multiple partners without any emotional commitment has no effect on the number of children a woman can bear. On the other hand, it does reduce her children's chances of survival, because if she has no partner with an emotional commitment to her and her children, then none of the fathers of her children is likely contribute to the burden of raising the children. If she is alone in the task of providing for her children, they are likely to have less protection and less food than they would if they had a father helping to raise them. Procreation in general is more resource-demanding for women than men because a woman can have only one child every nine months, during which she needs to invest a great amount of energy in pregnancy and childbirth. As a result, women need to be much choosier than men in mating, and they need to ascertain that their mates will be committed to them and to their children.

Cliché 3: Women are more anxious than men when it comes to their health and the well-being of their children, while men become more nervous than women when their health shows signs of failing.

The facts: The image and stereotype of the "caring and worrying" mother is common in many cultures, and for good reason. Because women are more limited than men in the number of children they can have, they need to invest more resources than men in protecting the children that they already have. This is the evolutionary source of the "caring and worrying mother" figure. When all her children have achieved adulthood and her years of fertility are behind her, usually when she is in her fifties, a woman's task in directly ensuring her genetic survival is over. But a man at that age can still contribute to his genetic survival by fathering more children. Only death or disease can limit his further fertility. In other words, from the perspective of genetic survival, from age fifty and above only men have "something to lose," which may be the source of male hypochondria in their later years.

To be continues next week with more Clichés