The Master And His Emissary, The Divided Brain, And The Making Of The Western World. Ian McGilchrist
Here’s what he says in the first 30-40 pages that fascinates me.
He thinks the 2 sides of the brain are involved in a power struggle where the balance of power has shifted to the left side in a way that we must strive to correct.
Almost everything you read in the popular press about lateralization (i.e., hemisphere differences) is wrong. Nearly every neural activity is happening in both sides. The one thing that’s correct in popular literature is that the right side is interested in the big picture and the left side in details.
Why are there 2 brains? This division of function seems to be important for all kinds of animals. Birds have one eye on the gravel, to find seeds, and the other on the sky, to watch for predators. Toads look at prey with one eye and other toads with the other eye.
The neuroscience details consist of many that I didn’t know: The right hemisphere is bigger, longer, wider. There is a twisted look to the whole brain when seen from below, called Yakovlevian torque. That amounts to a protrusion in the right frontal lobe, called the frontal petalia; and a similar bump on the left rear: occipital petalia. He reminds us that bigger usually means busier, as with hippocampal enlargement in London taxi drivers.
The right side has more white matter, meaning faster communication. It uses dopamine more while the left uses more noradrenaline. WRONG! (As often happens with me, I have an important detail wrong. I only noticed this in later pages when he said that the right side is important for analyzing new situations; and to support that functioning, he observed that norepinephrine was released on the right side, to keep neurons there from fatiguing. i.e., they keep firing on account of the NE.)
The two sides seem to be truly competing for control: the corpus callosum is mainly inhibitory in function, seemingly trying to shut the other side up. Even though one side might be more efficient at a task, if the other gets started first it will likely prevail and proceed. He says this situation can obtain in simple tasks even if one side is only 85 % as good at a job as the other.
Attention is not just another cognitive function. It determines how we see things. (He is referring here to which side of the brain we use.) A mountain might be a different thing to a prospector, a painter, or a native who thinks it’s the home of the gods. Science purports to get us closer to reality with its detachment, but this ‘view from nowhere’ is itself a value judgement. Attention is a ‘Way’ of looking that determines what we see. The trouble with us is that we’re using our left brains too much.
———————————————————-
That’s how things looked on March 7, 2026, after I made corrections. Here are additions based on notes made with pen and paper after the above.
What do the hemispheres do? The right is larger: wider and longer with smaller ventricles and more myelination. It is more broadly connected within itself and more connected to subcortical structures.
I have had a couple of quibbles to this point, actually.
1. On page 9 he says that there are more connections within the human brain than particles in the known universe. Well, are these connections not particulate? I suppose he must be referring to diverging chains of connections, where possible paths are permuted and counted; thus, a trivial arithmetic fact.
2. ‘There are no bits of cortex, only networks.’ What about columnar cortical organization? What about referring to any area or nucleus? What’s the point of telling us that the speech area on the left side is larger in utero at 31 weeks?
The ways that things are known about the two sides are:
Wada: sodium amytal, anaesthetic to a locale.
Transcranial stimulation.
ECS, in the old days.
Tachistiscopic presentation of stimuli. Fixate on the midline and get something flashed into left or right visual field before the eyes have time to move. Left visual field goes right side; and vice versa.
Dichotic listening: two auditory streams are presented, one to either ear. The left ear goes first to the right hemisphere and the left ear goes first to the right.
Callosotomy: split brain.
Right: responsible for alertness and vigilance, global attention.
Left: selectivity and divided attention; work is local and focused.
Hemineglect. There are startling drawings by patients with one side knocked out. If the left is missing, the patient draws a whole cat, a whole clock, a whole house. If the right brain is missing, he/she draws those images with the left side of the image missing. In discussing it, McG says it seems that the patient could have seen the whole image but was captivated by the stimuli from the left field.
Right is responsible for conjugate eye movements.
Chicks start out right-brain dominant, but the left inhibits the right and they change over time.
Caveats about imaging studies: 1) Smarter people and people with bigger brains show relatively less activity in regions known to be involved in a task. (This reminds me of a study of muscle activity in Olympic swimmers vs. good amateur swimmers: the Olympic ones used far fewer muscles to get the job done.) 2) Activity may mean inhibition. 3) Practice leads to less activity. 4) Other areas may be involved or are soon involved.
“Whatever I have brought into being for myself… is the remit of the left hemisphere, requiring a selective, highly focused attention. The right is on the look out, open to what exists apart from ourselves.”
The right can hold more information in memory and for longer times, making its perception of the whole better.
(This guy, MCg, loves one side of himself so much more than the other it’s hard not to recognize his bias. If the poor old left was not thrown under the bus again in the next paragraph, it would have been a mighty surprising one.)
A grounding and integrating role is played by the right. The order of events in perception is: right, left, right.’
Chicks are dominated first by the right, but then commissures develop and reverse this. Only with lesions of these does the initial order return.
Right underpins humor.
Left is too literal to make broad connections.
Right brain damage is like schizophrenia in that patients cannot understand implied meaning. Everything is literal.
Left: abstraction, decontextualization.
Right: actual relations in the world.
p. 51 “In general abstract concepts along with complex syntax are left hemisphere dependent. But…right inferiority depends on positive inhibition by the left. If the left is distracted or incapacitated the right [has] a more extensive vocabulary, including long, unusual and non-imageable words.
A rose, as a complex symbol is intelligible to the right.
A red light, meaning Stop, is simple and literal (left).
Right understands metaphor, integrating 2 seemingly unrelated concepts.
Left understands clichéd expressions. (What a goose & ass it is!)
Left is concerned with categories.
Right with individuals, uniqueness, the gestalt. McG tells us that categories do not exist in Nature but tyrannize understanding. (Hmmm.)
Capgrass syndrome\ belief that someone known is being represented by an imposter.
Frigoli syndrome\ delusional misrepresentation, belief that a person was seen all over town. A woman thought her husband was cavorting.
Left amasses impersonal info which is in the public domaine.
Right temporal lobe deals with personal and emotional info, and is implicated in a tendency to sadness.
Left is concerned with the fruit of human invention.
Right with what exists before us, after us and beyond us, Nature.
“If I imagine myself in pain I use both, but your pain is in my right.”
Patients with right frontal damage, but not left, become incapable of empathy.
Pars opicularis is part of Broca’s area on left that contains mirror neurons that fire when we see someone else do something, where we imitate finger movement. There is a corresponding area on the right. Only the right side imitates faces.
Right frontal pole (orbitofrontal cortex) has connection to limbic system; is involved with experience of emotions; regulates hypothalamic-pituitary axis; regulates autonomic responses; exerts inhibitory control over emotional responses.
Right interprets facial expression and gesture and tone of voice (prosody).
Right parietotemporal appreciates a mother’s voice.
prosopagnosia\ inability to recognize faces (be sure to ask someone: how’s your prosopagnosia progressing?)
Right: emotional expression, prosody, facial expression except!
Left: anger, which is dopamine-supported
Leftward cradling exposes an infant to the more emotional, left, side of our faces; and even chimps prefer it. Thus when we say gootchie gootchie goo, and wasm wasm wasms, or wazr, wazr wazrs, the child can see where it’s coming from, and what in store for the future.
Insight, Aha! is right, anterior, superior temporal. Usually consists in seeing the incongruity of previous assumptions.
Arithmetic: addition and subtraction on the right; multiplication on the left, where the tables are.
Deductive reasoning: right precuneus, deep in the parietal lobe, connected to the limbic system and sense of self. It is a hot spot, only quiet in vegetative states, sleep and anesthesia.
p. 70 “The left has a much more extensive vocabulary… (This seems to contradict what he said earlier, but he promises to devote a whole chapter to it later.) Of the right he says: “This silent hemisphere recognizes words and has a vocabulary… and even some aspects of syntax. Left… less concerned about meaning than the right hemisphere as long as it has control of the form and the system.” (This is an area where one waits for more information to assess what the deal is really.)
Left hemisphere damage that makes a person unable to speak may still allow him to sing the words of a song without difficulty.
Music: a Russian composer with a stroke on his left side did as well as ever.
amusia\ loss of ability to understand or perform music
Remarkable competence for music remains after left damage.
Right: Tone, timbre, pitch, as well as more complicated rhythms.
Simple rhythms are more broadly based.
However, this applies to amateurs. Professionals put more skill in the left side.
Zeitraffer phenomenon\ perceptual summation of frames in film.