Iain McGilchrist British psychiatrist and writer (b. 1953) Originally trained as a literature scholar Became a doctor and specialized in psychiatry Has done neuroimaging studies in the US	The Master and His Emissary: The Divided Brain and the Making of the Western World • 2009 A full summary of this book is found at https://www.updevelopment.org/the-master-his-emissary-full-summary/	The Matter With Things: Our Brains, Our Delusions, and the Unmaking of the World • 2021 A two-hour lecture by McGilchrist on this book at Ralston College in November 2021 can be found at this YouTube link

Hemispheric Asymmetry

(except where noted otherwise, all quotes from McGilchrist, 2021)

As we noted in the last class, the two hemispheres of the brain are asymmetrical (that is, have different physical characteristics). As McGilchrist (2021) points out: "The hemispheres differ in size, weight, shape, sulcal-gyral pattern (the convolutions on the cortical surface), neuronal number, cytoarchitecture (the structure at the cellular level), neuronal cell size, dendritic tree features, grey to white matter ratio, response to neuroendocrine hormones and degree of reliance on different neurotransmitters" (p. 44). [Animated gif of cerebral hemispheres: BodyParts3D, © The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan.]

The origin of these asymmetries is evolutionary and can be seen not only in humans but in other animals as well:

"[Asymmetry between the two hemispheres] was not an afterthought [in evolution]. It exists, as I mentioned earlier, in fish, amphibians, reptiles, birds, insects and nematode worms; but in fact the earliest known instance of a nervous system, that of Nematostella vectensis, a sea anemone over 700 million years old, already exhibits lateral asymmetry" (p. 88)

The lateralization of the brain's hemispheres allows each of them to specialize for different tasks and purposes.

Note, however, that the differences go beyond just what is processed, but much more importantly how reality is perceived. Each hemisphere actually experiences the reality of the world in a different way.

• The RH is a world of "individual, changing, evolving, interconnected, implicit, incarnate, living beings within the context of the lived world" (UP Development, 2022).

• The LH is "dependant on denotative language and abstraction, yields clarity and power to manipulate things that are known, fixed, static, isolated, decontextualized, explicit, disembodied, general in nature, but ultimately lifeless" (UP Development, 2022)

According to McGilchrist, the "Master" is the right hemisphere (RH) while the "Emissary" is the left hemisphere (LH).

In this metaphor, a "master" of a kingdom or a domain must be the center where all the information about the world comes together, is weighed, understood in context and used to make important decisions. A master politically is responsible for protecting his/her domain and making sure that the domain has what it needs to survive if it is attacked. To do this, the master uses an "emissary" -- that is, a delegate who is sent out into the world by the master with the mission to find out all the necessary information to be sent back to the master and which will allow the master to rule over the domain effectively. [Summary of McGilchrist's argument, not a quote.]

In a general sense, McGilchrist maintains that the RH is constantly scanning the overall environment for potential predators who might do harm or kill while the LH focuses more narrowly upon where prey might be found and captured before they can do damage.

Hemispheric Specializations

Take a look at this photograph. What immediately strikes you?

I suspect that many will look at this picture of the north side of Rossio Square in Lisbon, Portugal and notice the amazing ground pattern, how the alternating dark gray and white cobblestones create an effect that looks almost like the waves of the sea. The ground pattern fills almost the whole photograph.

Some might also take note of the National Theater of Dona (Queen) Maria II which sits at the end of the square. Built in a neoclassical style from 1842 to 1846, the theater displays an elegant balance of stonework and windows. The north end of the square also features a baroque fountain which mirrors the same type of fountain at the south end of the square. Of course, the fountain is situated so that it is exactly in the middle of the façade of the theater and, thus, creates even a greater sense of balance.

What do you not see usually when you first look at this picture?

• In the upper left/middle a couple is walking through the Square and the father is carrying a child

• In the pavement of the cobblestones, there seems to be a kind of sewer grating that allows workers to open up the ground and look below.

• In the extreme upper right of the photo there is a church on an overlooking hill.

In McGilchrist's analysis of hemispheric specialization, he argues that the RH takes in the overall view and has an appreciation of the pattern while the LH actively scans the world to look for details. Consider how you can alternate between attending to the general view versus making the decision to pay attention only to specific details.

Clinical Example of McGilchrist's Thesis

In the 1940s Swiss psychologist André Rey and his Belgian graduate assistant, Paul-Alexandre Osterrieth, created and standardized a set of figures to test individuals with different kinds of neurological diseases as well as to evaluate cognitive development in children. The result was the Rey-Osterrieth Complex Figure (ROCF) as seen at the top of the image (see below).

When used for clinical neuropsychogical testing, the person being tested is asked (1) to draw the image based on what they see in front of them (copy), (2) to draw it from memory immediately afterward (immediate recall), and (3) to draw it again from memory 30 minutes later (delayed recall). The three examples in the image illustrate what copying looks like when done by different individuals.

How do these three images differ?

• In the middle an older adult without any neurological disorder has copied the ROCF quite accurately.

• On the left, this 28-year-old male who has experienced damage to his left hemisphere copied the ROCF reasonably well: his copy maintains the overall configuration but there are numerous small errors involving the details within the original ROCF. Since his right hemisphere is intact, he was able to visualize the entire overall shape of the ROCF but had problems with small details.
  

• On the right, this 45-year-old woman with significant damage to her right hemisphere completely failed to copy the figure. Her drawing shows no awareness of the overall configuration or shape of the ROCF while there are a few details from the figure itself that are copied (and even here copied poorly). Because of the damage to her right hemisphere, she appears to have been unaware of the overall shape of the ROCF.
  

What are the multiple ways in which the LH and RH are different? Here is a list taken from Gilchrist (2021)

Left		Right
Principally concerned with manipulation of the world		Principally concerned with understanding the world as a whole and how to relate to it
Deals preferentially with detail, the local, what is central and in the foreground, and easily grasped		Deals principally with the whole picture, including the periphery or background, and all that is not immediately graspable
Looks for and deals with what is familiar		Is on the lookout for, better at detecting and dealing with, whatever is new; an ‘anomaly detector’ (Ramachandran)
Aims to narrow things down to a certainty; comes to ‘either/or’ decisions or collapses ambiguity in favor of a definite outcome		Opens things up into possibility. The RH can sustain ambiguity and the holding together of information that appears to have contrary implications, without having to make an ‘either/or’ decision, and to collapse it, as the LH tends to do, in favor of one of them.
Tends to see things as isolated, discrete, fragmentary…as put together mechanically from pieces, and sees the parts		Tends to see the whole…a complex union
Tends toward fixity and stasis (inactivity, slowness)		Tends toward change and flow
Tends to see things as explicit and decontextualized, this, it largely fails to understand metaphor, myth, irony, tone of voice, jokes, humor more generally, and poetry, and tends to take things literally		Tends to see things as implicit and embedded in a context
Tendency to prefer the inanimate (non-living); machines and tools are coded in the LH		Tendency to prefer the animate (living) though the animate is coded in both LH & RH
If offered a story whose episodes are taken out of order, it tends to regroup them so as to classify similar episodes together rather than reconstruct them in the order that has human meaning.		Understands narrative (a story or tale…how it begins, unfolds, and comes to a conclusion
Tends to categorize by using the presence or absence of a particular feature as its major strategy		Tends to categorize by referring to unique exemplars, what Wittgenstein called “a family resemblance” approach - it sees the Gestalt (overall configuration)
Prefers more general categories		Prefers more fine-grained categories as one approaches more closely uniqueness. RH damage leads to a loss of the sense of uniqueness or the capacity to recognize individuals altogether
Tends to focus on parts (arms, legs, etc.) from which the body must be constructed.		Contains the ‘body image’ (= both a visual image and multimodal schema of the body as a whole). Superior at reading body language and emotion as expressed in the face or voice
Superior at fine analytic sequencing, a larger linguistic vocabulary, more complex syntax		Better at pragmatics (the ability to understand the overall importance of an utterance in context). Understanding prosody (the musical aspect of language including tone, inflection, etc.) depends largely on the RH
Understands simple rhythms		Understands music in general
		Essential for “theory of mind” (= understanding another person’s point of view)
		Empathy, emotional receptivity and expressivity are greater in the RH
Sees things as they are “re-presented”, that is “present again” as already familiar abstractions or signs.		Better at seeing things as they are pre-conceptually, that is, fresh, unique, embodied, as they first present themselves to us
Unreasonably optimistic and lacking insight into its own limitations		More realistic, but tending toward pessimism (= “a tendency to see the worst aspect of things or believe that the worst will happen; a lack of hope or confidence in the future”)
Focusing upon where prey might be found and captured		Scanning the environment for potential predators

Keep in mind as you look at the differences above that each hemispheres has the ability both to excite and to inhibit the functioning of the other hemisphere.

Final Comment. McGilchrist (2009) argues that there has been a constant struggle between the hemispheres for dominance. In this struggle, certainly not enough time has occurred in human history to affect the genetic or evolutionary basis for the two hemispheres. However, particularly in the West, the development of human culture has shaped human life in such a way that the functions of the left hemisphere have been prized and reinforced far more than the functions of the right hemisphere. In his argument, the "emissary" has gained control over the "master".  Part 2 of McGilchrist's (2009) book charts the ways in which the brain has shaped our world (and, indeed, how the world has shaped how the brain is used functionally). A summary of his argument can be found at this link.