PPP, Part 25, Hemisphere Specialization

Greetings, Friendlies. :)

Hemisphere Specialization. The idea that the left and right brain hemispheres have different structural and functional roles, and that these differences are manifest in our lived experience.

You’ve probably heard this kind of thing before: “artists are right-brained, analysts are left-brained”. That’s actually not accurate, that artists are right-brained and analysts are left-brained, but the idea in pop culture is in the same ballpark as the one we’ll look at. :)

We’ll unpack the “So what?” question in future posts. For now, here are specializations I’ve begun collecting from [1] Iain McGilchrist’s The Master and His Emissary and [2] Michael S Gazzaniga’s Who’s In Charge?. I bet you’ll see the so what. :)))

With friendliness!

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Left Hemisphere:

• “the left-hemisphere view is designed to aid you in grabbing stuff. Its purpose is utility and its evolutionary adaptation lies in the service of grasping and amassing ‘things’.” [1] 
• [Shan’s Note: though he doesn’t say so here, it may be the left hemisphere that is “thing-ifying” the world in the first place?]
• “unreasonable optimism, manipulation, disembodiment, literalism, and preoccupations with detail, theory and body parts.”  [1]
• “the left hemisphere is more likely than the right to get angry or dismissive, jump to conclusions, become deluded or get stuck in denial.”  [1]
• “the left-hemisphere view offers simple answers.”  [1]
• “prizes consistency above all” [1] 
• “claims to offer the same mechanistic models to explain everything that exists.” [1] 
• “When this sort of thinking encounters a problem in reconciling apparent irreconcilables – for example, matter and consciousness – it simply denies that one element or the other exists.” [1]  
• “the left hemisphere’s point of view, which is easily articulated and unambiguous”  [1]
• “The left hemisphere relies on concatenations of serial propositions and the literal aspects of language to make meaning explicit”  [1]
• “The left hemisphere is the speaking hemisphere” [Shan’s Note: Except in some cases of left-handed folks and some cases where the left-hemisphere is damaged.] [1]
• “the right hemisphere tends to ground experience; the left hemisphere then works on it to clarify, ‘unpack’ and generally render the implicit explicit; and the right hemisphere finally reintegrates what the left hemisphere has produced”  [1]
• “the left hemisphere, which underwrites [a fragmented view of the world], is both literally more limited in what it can see, and less capable of understanding what it does see, than the right – and, to cap it all, is less aware of its own limitations”   [1] [Shan’s note: See the Anomaly Detector below.]
• “The cerebral and the abstract – for example, management and its systems” [as opposed to hands-on task or craft that management supports.]  [1]
• “The left hemisphere’s view is exclusive, ‘either/or’, analytic and fragmentary – but, crucially, unaware of what it is missing.”  [1]
• [Shan’s Note: In _Who’s In Charge_, Gazzaniga also gives examples in Split Brain Patients indicating that the Left Hemisphere was unaware of having lost connection with the Right Hemisphere. AKA, it is unaware of what is missing.] [2]
• Reductionist [1] [2]
• “the left hemisphere is, in the most down-to-earth, empirically verifiable way, less reliable than the right – in matters of attention, perception, judgment, emotional understanding, and indeed intelligence as it is conventionally understood.”  [1] 
• “the left hemisphere’s vision of a mechanistic world, an atomistic society, a world in which competition is more important than collaboration; a world in which nature is a heap of resource there for our exploitation, in which only humans count, and yet humans are only machines – not even very good ones, at that”  [1]
• “Maths and science are not primarily dependent on the left hemisphere, but draw in different respects on both hemispheres.”  [1]
• “the left hemisphere frequency-matches”   [2]
• “falsely identifies similar but novel stimuli as being the same as previously seen stimuli.” and “the left hemisphere tends to falsely recognize items that are similar as being the same.”   [2]
    • Example: “When asked to decide whether various items appeared in a series of items previously shown to it, the right hemisphere is able to correctly identify items it saw previously and to reject new items. “Yes, there was the plastic spoon, the pencil, the eraser, and the apple.” The left hemisphere, however, tends to falsely recognize new items when they are similar to previously presented items, presumably because they fit into the schema it has constructed. Yep, they are all there: the spoon [but we substituted a silver one for a plastic one], the pencil [although this one is mechanical and the other was not], the eraser [though it is gray and not pink], and the apple.”  [2]
• “It gets the gist of the situation from all the input, tries to find a pattern, and puts it together in a makes-sense, interpretation.”  [2]
    • Example: “A box of candy presented to the right hemisphere is a box of candy. The left hemisphere can infer all sorts of things from this gift.”  [2]
• “The left hemisphere … specialized in language, speech, … After commissurotomy, the verbal IQ of a patient is unchanged”  [2]
• “[the] left hemisphere could generate voluntary facial expressions”. [That is, if you ask someone someone to smile, it is the left hemisphere that generates the facial movements. The right hemisphere _can_ generate a spontaneous smile.]  [2]
• Making inferences? I’m not confident about this one, but Gazzaniga says:
    • “when we flashed the word pan to the right hemisphere, the left hand would point to a pan. Next, we flashed the word water, and the left hand pointed to water. So far, so good: the right hemisphere could read the words and relate the words to the pictures. When we flashed the two together, however, the left hand could not put them together into the concept of water in a pan, and pointed to the empty pan picture. This water/pan task was quickly solved by the left hemisphere.”  [2]
• It seems from _Who’s In Charge_ that the Interpreter Module is constructed in the left hemisphere. [2] See Viññāṇa, CogSci Support for “Consciousness Of” for some explication. 
• “the application of logical rules and conceptual knowledge to the interpretation of events”  [2]
• Makes-sense story. “this left-brain interpretive process that we have takes all the input, puts it together in a makes-sense story”   [2]
• “Patients with left frontal lobe lesions tend not to be able to engage in denial, rationalization, or confabulatory “gap-filling””  [2]
• The hemispheres seem to have two different types of processes for causality. The left hemisphere uses “causal inference”. [2] 
    • Example: “Two small boxes, a red one and a green one, were suspended above a larger box. When one or the other of these boxes dropped down and touched the larger box, either independently or together, the larger box would light up only if it were touched by the green box. The left hemisphere can make the causal inference right away that the larger box must be touched by the green box for it to light up, but the right hemisphere simply can’t do it.” [2]

Right Hemisphere:

• “If a neuropsychologist had to choose three things to characterise most clearly the functional contribution of the right hemisphere, they would most probably be the capacity to read the human face, the capacity to sustain vigilant attention, and the capacity to empathise.”  [1]
• “realism, the appreciation of uniqueness, music and time, a sense of humour, a capacity for reading body language, sustaining attention and the fight-or-flight mode;” [1] 
• “The left hemisphere relies on concatenations of serial propositions and the literal aspects of language to make meaning explicit; by contrast, metaphor and narrative are often required to convey the implicit meanings available to the right hemisphere”  [1]
    • “The attempt to make the implicit explicit [what the left hemisphere is doing] radically alters its nature; as a result, finding the language to put across the way of being of the right hemisphere is simply harder than doing so for the naturally explicit left hemisphere.” [1] 
• “the right hemisphere tends to ground experience; the left hemisphere then works on it to clarify, ‘unpack’ and generally render the implicit explicit; and the right hemisphere finally reintegrates what the left hemisphere has produced with its own understanding, the explicit once more receding, to produce a new, now enriched, whole.”  [1]
• The anomaly detector. “the right parietal lobe has a system that he calls an anomaly detector, which squawks when the discrepancies [between our views/beliefs and reality] get too large. … This would account for the observation that patients with right parietal lobe lesions can have such outrageous, no-holds-barred stories coming out of their left hemisphere, unconstrained by their right-hemisphere anomaly detector, while this doesn’t happen with left-hemisphere lesions, where the right, totally accurate, and exacting system is fully operative.”  [2]
•  The right hemisphere’s view is inclusive, ‘both/and’, synthetic, integrative  [1]
• “the right hemisphere, which is more multifaceted and harder to articulate, and is already inclusive of the apparently incompatible left hemisphere’s point of view. This virtue makes it immediately vulnerable to the charge of inconsistency” 
• “it’s not true that the right hemisphere has no language (it usually has no speech, a different matter): it understands many of the subtlest and most important elements of language better than the left.” 
• The hemispheres seem to have two different types of processes for causality. The right hemisphere uses “Perceptual Causality”. [2] 
    • “Michotte’s balls. If after observing a green ball on a screen move toward a red ball, stop when it contacts it, and then the red ball immediately moves away, most people report that the green ball caused the red ball to move. This is perceptual causality: It is the direct perception, in this case by observation, that some action occurred as a result of physical contact. If, however, a time gap takes place between when the balls contact each other and when the red ball moves off, or if the balls don’t actually touch and the red ball moves off, most report that there is no causal relationship. It is the right hemisphere that can see this difference.” [2] 
• McGilchrist says the left hemisphere functioning highlights “The cerebral and the abstract – for example, management and its systems”. Though he doesn’t say so in this quote, I assume he will eventually say that the right hemisphere highlights the physical and concrete. The tasks and crafts that are managed.   [1]
• McGilchrist says “We also need to be aware of the sheer extent to which the left hemisphere is, in the most down-to-earth, empirically verifiable way, less reliable than the right – in matters of attention, perception, judgment, emotional understanding, and indeed intelligence as it is conventionally understood.” So we can say the right hemisphere is more reliable in matters of attention, perception, judgment, emotional understanding, and conventional intelligence?  [1]
• Maths and sciences “draw in different respects on both hemispheres.”  [1]
• “The right hemisphere lives a literal life. When asked to decide whether various items appeared in a series of items previously shown to it, the right hemisphere is able to correctly identify items it saw previously and to reject new items. “Yes, there was the plastic spoon, the pencil, the eraser, and the apple.” The left hemisphere, however, tends to falsely recognize new items when they are similar to previously presented items … Yep, they are all there: the spoon [but we substituted a silver one for a plastic one], the pencil [although this one is mechanical and the other was not], the eraser [though it is gray and not pink], and the apple.    [2]
• “As a consequence of not being able to draw inferences, the right hemisphere is limited by what it can have feelings about. A box of candy presented to the right hemisphere is a box of candy. The left hemisphere can infer all sorts of things from this gift.”  [2]
• the right hemisphere was superior at visual spatial skills.   [2]
    • “While [the right hemisphere] could easily put together a series of colored blocks to match a pattern in a picture … the left hemisphere, took forever to solve the puzzle. In fact, one patient had to sit on his left hand [which is under right hemisphere control] to prevent it from coming up and trying to solve the problem.”  [2]
    • “The [right hemisphere] could copy and draw three-dimensional pictures, but the [left hemisphere], that one that so easily can write a letter, could not draw a cube.”   [2]
• “The right hemisphere turned out to be specialized for such tasks as recognizing upright faces, focusing attention, and making perceptual distinctions.”   [2]
• the [right hemisphere] is a maximizer, the [left hemisphere] frequency matches.  [2]
• “the right hemisphere is better than the left at a variety of visual tasks that involve advanced processing.” [2] 
    • “The right hemisphere is easily able to do tasks that involve discriminations that are spatial in nature, such as detecting whether two images are identical or mirror-reversed, detecting small differences in line orientation,13 and mental rotation of objects”  [2]
• “The right is also superior at temporal-discrimination tasks such as judgments as to whether two objects appear on a screen for equal or unequal amounts of time.”  [2] 
• “It also turns out that the right hemisphere is exceptional at perceptual grouping. For example, if you show partially drawn figures to the right hemisphere, it can easily guess what they are, but the left hemisphere can’t guess until the figure is nearly completely drawn.”  [2]
• The right hemisphere is subject to some aspects of visual illusion that the left is not. 
    • “illusory line motion. This occurs when a line is shown on a visual display in its entirety, all at once, but to the observer it appears to propagate from one end. … If the line flashes between two dots of different colors or widths, it appears to propagate from the dot that it matches. This involves higher-level processing; the right hemisphere sees this illusion, but the left does not.”  [2]