This article is an excerpt from the Shortform book guide to "The Master and His Emissary" by Iain McGilchrist. Shortform has the world's best summaries and analyses of books you should be reading.
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What’s the difference between the left and right brain? Is one hemisphere more important than the other?
In his 2009 book, The Master and His Emissary, Iain McGilchrist cites an array of scientific evidence intended to dispel the myth that the right hemisphere is “minor.” He contends that the right brain is actually dominant over the left brain and explains five significant differences between the hemispheres.
Keep reading to learn about five left and right brain differences that speak to McGilchrist’s intriguing argument.
Left and Right Brain Differences
We’ll examine five of the left and right brain differences that McGilchrist discusses—differences in understanding meaning, perceiving objects, grasping coherent wholes versus individual parts, processing emotions, and thinking intuitively. These brain hemisphere differences illustrate one of McGilchrist’s key claims: The myth of left-hemisphere superiority is misguided, as the right hemisphere is responsible for several of the brain’s most essential functions.
Difference #1: Implicit vs. Explicit Meaning
Despite the popular caricature of the right hemisphere as “silent,” McGilchrist contends that it plays a crucial role in understanding language. By examining the effects of injuries to the right and left hemispheres, he argues that, though the left hemisphere grasps formal linguistic rules, only the right hemisphere grasps the implicit meaning that language conveys.
He notes that, when people suffer from right hemisphere damage (and therefore rely on their left hemisphere), they often speak sentences that are syntactically and grammatically flawless but nonsensical. In a similar vein, children that suffer right hemisphere injuries struggle to understand entire sentences, even when they know each of the individual words.
McGilchrist concedes that the left hemisphere can understand denotative meaning. For this reason, the left hemisphere has a much larger vocabulary than the right hemisphere. But he reiterates that only the right hemisphere is able to understand the meaning of those terms in context.
Likewise, McGilchrist asserts that only the right hemisphere can grasp metaphors because metaphors don’t depend on the denotative meaning of words, but rather on their connotative meaning. The upshot, according to McGilchrist, is that the right hemisphere is crucial for understanding the world because we can’t understand the world without metaphors. After all, many aspects of life—such as beauty, love, and pain—can’t be described through denotative language alone. To understand and describe such phenomena, McGilchrist suggests we need to use metaphor.
Difference #2: Abstract vs. Contextual Perception
The right hemisphere’s ability to understand meaning in context hints at another difference between the hemispheres: Only the right hemisphere perceives objects in context. Specifically, McGilchrist argues that the right hemisphere sees objects within broader surroundings, while the left hemisphere sees objects abstracted from those surroundings.
Individual Objects vs. Categorizations
Because the right hemisphere prefers to examine objects in context, while the left hemisphere prefers abstractions of concrete objects, a related difference arises: The right hemisphere thinks in terms of individual objects, while the left hemisphere thinks in terms of broader categories.
Difference #3: Wholes vs. Individual Parts
In addition to perceiving objects in context as opposed to abstracting them, another perceptual difference arises with respect to parts and wholes. According to McGilchrist, because of its preference for abstraction, the left hemisphere breaks objects into their constituent parts while the right hemisphere, with its preference for context, focuses on the whole picture that these parts compose.
To show as much, McGilchrist cites drawings from patients with hemisphere damage. Those with right hemisphere damage were unable to draw coherent wholes; when asked to draw a person, for instance, they couldn’t accurately place the body parts to create a unified human figure. Those with left hemisphere damage, by contrast, could draw coherent wholes, but with a lack of detail in individual parts; when asked to draw a tree, for instance, such individuals often drew an outline of a tree that lacked details on individual branches or leaves.
Similarly, patients with damage to either hemisphere had differing abilities to recognize parts and wholes. For instance, McGilchrist cites a patient with right hemisphere damage who could only recognize a house in a picture by recognizing its chimney (a part) and then inferring that it must be a house.
| Hemisphere Differences in Philosophical Debates on Wholes vs. Parts It’s possible that the hemisphere differences McGilchrist describes have influenced philosophical debates, such as those at the heart of mereology—the study of the relationship between parts and the wholes they compose. On the one hand, some philosophers endorse mereological nihilism, the position that individual parts never make up a composite whole. Though arguments for mereological nihilism are many, one common argument contends that we should reject the existence of wholes because they would be causally redundant. For example, because we can (in theory) explain how a baseball shatters a window by appealing to the atoms that make up the baseball, we don’t need to posit that a baseball (the whole) exists; we can claim that only the atoms (the parts) exist. This radical position, which only recognizes parts and not wholes, might stem from an excess of the left hemisphere. By contrast, others endorse mereological universalism, the position that any set of individual parts always makes up a composite whole. One common line of reasoning claims that any distinction between parts that do compose a whole and parts that don’t would be arbitrary; in turn, parts must always compose a whole. So, for example, there exists a composite whole made up of (say) your couch, television, and toilet. This view, it would seem, could stem from an excess of the right hemisphere, which focuses on wholes rather than parts. |
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Here's what you'll find in our full The Master and His Emissary summary:
- How pop psychology has given us the wrong impressions of the brain's hemispheres
- Why the right hemisphere is actually more important than the left
- What would happen if left-hemisphere thinking took over the world
