hemispheric organization and the 10% myth
May. 9th, 2005 06:32 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ashnistrikeIn response to a request on ![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
ozarque's journal, an attempt to dispell a couple of popular myths about brain structure.
Let's start with hemispheric organization. Pop psychologists can spend hours discoursing on right-brain/left-brain dichotomies. Ostensibly, the left hemisphere is responsible for analytical, intellectual, rational thought. The left side of your brain is staid and conservative, unemotional, and quite possibly a tool of the patriarchy. The right hemisphere, by constrast, is said to be creative, holistic, intuitive and emotional. It is probably planning the overthrow of all conventional ideas about politics and art at this very moment. Furthermore, everyone's thought processes reflect the dominance of one hemisphere over the other. In order to increase your creativity, you must practice your right-brain skills (it's assumed that most people in patriarchal American culture have ended up left-brained, or at least that there aren't any artists with a desperate yen to improve their mathematical abilities). Obviously there's an assumption here that hemispheric dominance is learned. You can be whatever you want, with enough effort. Or you can just spend all day taking internet tests that tell you if you're right-brained or left-brained.
My lovely Intro to Learning textbook (An Introduction to Theories of Learning, by B.R. Hergenhahn & Matthew H. Olson) calls this "dichotomania." It's based on a kernel of truth, but that kernel has gotten pretty buried.
Your cerebral cortex is, indeed, divided into two hemispheres. The do have functional assymmetries, the most obvious of which is that each is responsible for the opposite side of the body. The right hemisphere takes sensory input from, and sends motor output to, the left side of the body, and vice versa. This is so weird that it's been suggested that in the distant evolutionary past, vertebrate heads somehow mutated and flipped around 180 degrees. If you are strongly right- or left-handed, the motor cortex on the opposite side of your brain will be slightly more developed in the section responsible for your arm and hand.
The major difference between the right and left hemispheres is that, in most people, the left hemisphere performs most language functions. All speech production and much of comprehension originate in this hemisphere. This is where you store vocabulary, put together sentences, piece out meanings. The equivalent areas of the right hemisphere are responsible for what Ozarque refers to as non-verbal communication--particularly the "tune" of your speech. Damage this area, and you'll speak with completely flattened affect, or be unable to tell the difference between "You ate the last donut" and "You ate the last donut?!!!" Musical tunes also seem to be more a right-hemisphere thing.
For some people (about 15% of left-handers), language is in the right hemisphere instead. Another 15% of left-handers have language evenly divided across hemispheres. This doesn't appear to have any effect on your thought processes--it's only important if you go in for brain surgery.
Overall, the left hemisphere does seem to be more detail-oriented, and obviously more verbal. Processing in the right hemisphere does seem to be more holistically-oriented. However, there is no basis for the idea that people have any sort of hemispheric dominance. None. Most thought processes involve both hemispheres to some extent. Under normal circumstances, they communicate constantly, so that everything gets both broken down into details as well as perceived as a whole. You've got to be able to do both of those things in order to, for example, understand that the thing in front of you right now is a computer.
In fact, there's some evidence that creativity is a function, not of right-brain activity (where would that leave writers?), but of cooperative activity between the two hemispheres. The primary connection between the two is a wad of axons called the corpus callosum; there's been some demonstration that people who score high on tests of creativity have slightly thicker CCs. (Standardized tests of creativity: a rant for another time).
Now, certainly, some people tend to think more intuitively, some more analytically. It's the difference between someone who enjoys painting and someone who really loves computer programming or calculus. There are also people who are pretty good (or pretty bad) at both. What you like to do, or what you're good at, is a more complicated issue than which hemisphere is lording it over the other one.
The 10% myth explanation is, happily, shorter. You use all of your brain. You don't the whole thing all the time (that would be severe and probably fatal epilepsy), but everything that's in there right now has a function, and gets called on on a semi-regular basis. We know this because any connections that don't get used become weaker over time and eventually go away (we're talking about the learning and reasoning areas here--what happens to old memories is a more complicated question). This is especially notable in infants. A baby starts with an enourmous number of connections, and much of their initial learning is a matter of pruning connections that don't actually reflect the universe they find themselves in. It's like carving a statue from a block of marble, chipping away those bits of stone that aren't part of the image of a horse (or whatever you feel like carving). The only difference is that you also regularly grow new connections, as you learn things you didn't know before. The phrase "use it or lose it" is an apt one here. Skills that are used become stronger; skills that are neglected fade.
We know, roughly, what most of your brain does. That is, we can point to a section that's responsible for movement, and another that does something with language, and another that lights up when you do crossword puzzles and we're still arguing over what that means. Obviously the map is more detailed in some places than in others. However, if someone makes an argument for psychic abilities that starts with "scientists only know what 10% of your brain does--you must be doing something with the rest of it," then you probably want to look around for a better class of parapsychologist.
ozarque's journal, an attempt to dispell a couple of popular myths about brain structure.Let's start with hemispheric organization. Pop psychologists can spend hours discoursing on right-brain/left-brain dichotomies. Ostensibly, the left hemisphere is responsible for analytical, intellectual, rational thought. The left side of your brain is staid and conservative, unemotional, and quite possibly a tool of the patriarchy. The right hemisphere, by constrast, is said to be creative, holistic, intuitive and emotional. It is probably planning the overthrow of all conventional ideas about politics and art at this very moment. Furthermore, everyone's thought processes reflect the dominance of one hemisphere over the other. In order to increase your creativity, you must practice your right-brain skills (it's assumed that most people in patriarchal American culture have ended up left-brained, or at least that there aren't any artists with a desperate yen to improve their mathematical abilities). Obviously there's an assumption here that hemispheric dominance is learned. You can be whatever you want, with enough effort. Or you can just spend all day taking internet tests that tell you if you're right-brained or left-brained.
My lovely Intro to Learning textbook (An Introduction to Theories of Learning, by B.R. Hergenhahn & Matthew H. Olson) calls this "dichotomania." It's based on a kernel of truth, but that kernel has gotten pretty buried.
Your cerebral cortex is, indeed, divided into two hemispheres. The do have functional assymmetries, the most obvious of which is that each is responsible for the opposite side of the body. The right hemisphere takes sensory input from, and sends motor output to, the left side of the body, and vice versa. This is so weird that it's been suggested that in the distant evolutionary past, vertebrate heads somehow mutated and flipped around 180 degrees. If you are strongly right- or left-handed, the motor cortex on the opposite side of your brain will be slightly more developed in the section responsible for your arm and hand.
The major difference between the right and left hemispheres is that, in most people, the left hemisphere performs most language functions. All speech production and much of comprehension originate in this hemisphere. This is where you store vocabulary, put together sentences, piece out meanings. The equivalent areas of the right hemisphere are responsible for what Ozarque refers to as non-verbal communication--particularly the "tune" of your speech. Damage this area, and you'll speak with completely flattened affect, or be unable to tell the difference between "You ate the last donut" and "You ate the last donut?!!!" Musical tunes also seem to be more a right-hemisphere thing.
For some people (about 15% of left-handers), language is in the right hemisphere instead. Another 15% of left-handers have language evenly divided across hemispheres. This doesn't appear to have any effect on your thought processes--it's only important if you go in for brain surgery.
Overall, the left hemisphere does seem to be more detail-oriented, and obviously more verbal. Processing in the right hemisphere does seem to be more holistically-oriented. However, there is no basis for the idea that people have any sort of hemispheric dominance. None. Most thought processes involve both hemispheres to some extent. Under normal circumstances, they communicate constantly, so that everything gets both broken down into details as well as perceived as a whole. You've got to be able to do both of those things in order to, for example, understand that the thing in front of you right now is a computer.
In fact, there's some evidence that creativity is a function, not of right-brain activity (where would that leave writers?), but of cooperative activity between the two hemispheres. The primary connection between the two is a wad of axons called the corpus callosum; there's been some demonstration that people who score high on tests of creativity have slightly thicker CCs. (Standardized tests of creativity: a rant for another time).
Now, certainly, some people tend to think more intuitively, some more analytically. It's the difference between someone who enjoys painting and someone who really loves computer programming or calculus. There are also people who are pretty good (or pretty bad) at both. What you like to do, or what you're good at, is a more complicated issue than which hemisphere is lording it over the other one.
The 10% myth explanation is, happily, shorter. You use all of your brain. You don't the whole thing all the time (that would be severe and probably fatal epilepsy), but everything that's in there right now has a function, and gets called on on a semi-regular basis. We know this because any connections that don't get used become weaker over time and eventually go away (we're talking about the learning and reasoning areas here--what happens to old memories is a more complicated question). This is especially notable in infants. A baby starts with an enourmous number of connections, and much of their initial learning is a matter of pruning connections that don't actually reflect the universe they find themselves in. It's like carving a statue from a block of marble, chipping away those bits of stone that aren't part of the image of a horse (or whatever you feel like carving). The only difference is that you also regularly grow new connections, as you learn things you didn't know before. The phrase "use it or lose it" is an apt one here. Skills that are used become stronger; skills that are neglected fade.
We know, roughly, what most of your brain does. That is, we can point to a section that's responsible for movement, and another that does something with language, and another that lights up when you do crossword puzzles and we're still arguing over what that means. Obviously the map is more detailed in some places than in others. However, if someone makes an argument for psychic abilities that starts with "scientists only know what 10% of your brain does--you must be doing something with the rest of it," then you probably want to look around for a better class of parapsychologist.
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no subject
Date: 2005-05-10 12:38 am (UTC)no subject
Date: 2005-05-10 06:17 am (UTC)no subject
Date: 2005-05-10 01:30 am (UTC)I would like to point out, as a borderline mathematician, that most people's impression of what mathematics is, and what kinds of abilities it requires, are quite different from what mathematicians think it is and what abilities it requires.
I agree that if one is programming or solving a calculus problem, analytical ability is needed. But most mathematicians tend to regard that as filling in the details. Solving big problems is very much a creative and intuitive art.
I highly recommend experience in high-level mathematics, because it is superb practice in thinking, both analytically and creatively, and knowing when one or the other is required. It's also the area in which I'm most aware of the mental processes involved in turning analytical, step-by-step problem solving into an intuitive grasp that allows creative leaps.
And then one has to go back and fill in the analytical details of the creative leap, yes :-).
no subject
Date: 2005-05-10 06:21 am (UTC)no subject
Date: 2005-05-10 06:27 am (UTC)no subject
Date: 2005-05-10 09:48 am (UTC)And yes, Zeki (the cat) is very cute when he's not terrorising the other two.
no subject
Date: 2005-05-10 04:35 pm (UTC)no subject
Date: 2005-05-11 12:32 pm (UTC)I admit I'm not up to date on evolutionary psychology, partly because I've never been impressed in the past, and that's included several rounds of "but it's so much better now" that still didn't impress me. So, for good or bad, I'm hard to drag back for another round.
The hobbits are very cool, but I'm hanging back a bit because the reports seemed a bit incomplete to me. I want to see how the scientific consensus develops.
Thank you!
Date: 2005-05-10 01:55 am (UTC)I would chime in with aquari's comments about math. This reminds me that I've noticed myself using atypical (for me) sensory language to try to describe proof-writing to students. I end up using much more touch language ("Does this argument feel like it's going in the right direction?"), and even talking about the "flavor" of a certain approach.
I'm hoping not to remain "anonymous" forever; after exams are graded I plan to explore the options.
Thanks to you I now harbor n - 2 misconceptions. Thanks again! Allison
oops
Date: 2005-05-10 01:56 am (UTC)Re: oops
Date: 2005-05-10 09:50 am (UTC)Re: Thank you!
Date: 2005-05-10 06:26 am (UTC)Just a quick point, and not intended as a criticism--psychology is a science. It's a younger one, and a harder one to control, than what are affectionately known as the "hard sciences" (which is what I think you meant), but a science nevertheless and working on becoming a better one.
Re: Thank you!
Date: 2005-05-10 04:45 pm (UTC)Allison
I love you!
Date: 2005-05-10 02:12 am (UTC)I do love you, BUT...
Date: 2005-05-10 01:11 pm (UTC)Re: I do love you, BUT...
Date: 2005-05-10 04:32 pm (UTC)On parts of the brain that take over lost functions: two answers. One is that they may not have been there before--over the last ten years we've discovered that even adults can grow new connections, even new neurons, in response to both normal learning and damage. Why does this work sometimes and fail other times? We don't know; ten years ago my college professors told me it didn't happen at all. The second answer is that there is also probably some redundancy built into your representations, and some room to coopt redundant bits to replace lost function. How much redundancy, and why? Again, we don't know yet.
All the spike-through-the-head-and-survived stories I know are either fairly old or involve personality changes that wouldn't necessarily show up on an IQ test. I'd be interested to hear one that contradicted this. Do you have any reference for the case you're thinking of, or recollection of more details?
Re: I do love you, BUT...
Date: 2005-05-10 05:14 pm (UTC)I haven't looked at this stuff since I was in college. I'm delighted to hear there's been so much progress in the field since then! (I did graduate work in clinical psych type stuff, but that was definitely a focus on therapy and psychopathology of the more Fruedian type, rather than brain studies.)
((Which actually made me chuckle a bit when you said that psychology wasn't a "soft" science above. Brain studies? Cognitive psych? Sure, I can see that. But there are whole branches of psychology that are very soft...like the entire branch of psychodynamics...(("Neurosis is a result of empathic failure on the part of attachment objects during childhood...")) And I love that stuff, too, oh I so do...))
Re: brain cells
Date: 2005-05-11 12:55 pm (UTC)I am asking because of experience of caring for an elderly relative with Multi-Infarct Dementia. (Unfortunately the doctor claimed that the dementia had a psychiatric cause and was the fault of the carer.)
The dementia sufferer had a series of infarcts, losing areas of memory and appearing to regress to a very young age; however, she would then apparently gradually remember skills etc. (She was about 64 at first onset.) She did interact with her carer continually and it seems quite possible that she really relearned. Her personality changed a great deal during this period.
She was finally referred to a Neurologist at age 74, and was diagnosed as suffering from Multi-Infarct Dementia "with no mind left to save". It was explained that her "faints" were really infarcts - clots blocking the blood suppy to various parts of the brain, with the affected parts dying in consequence. She went into professional Care and made no further "recoveries" until her death at 79.
At that time it seemed to be accepted wisdom that brain cells do not regenerate and I had no explanation for what had taken place - questions were brushed aside.
Re: brain cells
Date: 2005-05-11 03:08 pm (UTC)When I started college (in 1993), the cut-off age for new neuronal growth was considered to be adolescence at the latest. Since then, new findings keep pushing the boundary, and at this point I really wouldn't feel comfortable saying there's any upper limit at all. However, it does look like it's easier for younger people and especially children to regrow neurons and compensate for damage.
In general, it's easier for anyone to compensate if they have stimulation, and someone trying to help them relearn. Even under the best possible circumstances, however, there are going to be limits on what can be regained.
Caveat: My own work is in behavioral experimentation rather than neuroscience. Your question is an area I know a reasonable amount about, but it's not my specific expertise.
Re: brain cells
Date: 2005-05-19 07:49 pm (UTC)My degree was in Social Science - I couldn't work after graduation because of family responsibility and disability but there may be some overlap in our subjects. I found some of your posts facinating. Please may I add you to my friends list?
Re: brain cells
Date: 2005-05-19 08:59 pm (UTC)What aspect of social science? I find the study of what humans do in groups, and how it differs (and doesn't differ) from what they do as individuals, fascinating.
Re: brain cells
Date: 2005-05-19 09:30 pm (UTC)I was thought a bit of a radical for pointing out that all the studies were of adult male criminals but delinquents are children - and you can usually count the number of adult male criminals who are the major influence in rearing children on the fingers of one foot! Have you ever been interested in the psychology of social exclusion? I'll bore on about it at length unless actually stopped!
I also keep tropical fish and got very interested in Ethology and the learning process vs instinct - as a kind of hobby.
Re: brain cells
Date: 2005-05-19 10:46 pm (UTC)no subject
Date: 2005-05-11 04:29 am (UTC)Followed your link from