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How researchers discovered we have “two brains”

www.bbc.com · 106 HN points · 0 HN comments
HN Theater has aggregated all Hacker News stories and comments that mention www.bbc.com's video "How researchers discovered we have “two brains”".
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www.bbc.com Summary
BBC Reel meets the 'father of split-brain syndrome' Mike Gazzaniga, to understand how researchers discovered how we all have 'two brains'.

Video by Melissa Hogenboom & Pierangelo Pirak
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Mar 28, 2019 · 106 points, 59 comments · submitted by hanniabu
corysama
Common human behavior is a lot more schizophrenic than any of us are comfortable with understanding. I recommend the book "Hare Brain Tortoise Mind" to everyone who will listen. It explains one form of multi-mindedness that leads to you getting your best insights while in the shower --what it's good at and what it's not.

"The Man Who Mistook His Wife For a Hat" is another classic.

maddyboo
Another interesting read is “The Origin of Consciousness in the Breakdown of the Bicameral Mind” by Julian Jaynes, which outlines hypothesis of bicameralism [1].

[1] https://en.wikipedia.org/wiki/Bicameralism_(psychology)

x3n0ph3n3
The hypothesis of bicameralism is mostly debunked, though.
None
None
725686
Any references?
x3n0ph3n3
Did you not look at any of the criticisms included on the wikipedia page? "Debunked" may have been overly strong, but it certainly lacks evidence and there are some good arguments against it.

[1] https://en.wikipedia.org/wiki/Bicameralism_(psychology)#Issu...

PixyMisa
I'd say "debunked" is putting it mildly. "Vacuous nonsense fuelled entirely by cherry picking and special pleading" is the phrase I'd use. See for example his response to the Epic of Gilgamesh.
devoply
schizophrenia in japan is called integration disorder. meaning the many different parts of the mind, or many minds, are not integrating into a single mind.
azeirah
That's slightly odd to me, that description sounds like it would better for a dissociative disorder.
dmitryminkovsky
Reminds me of something from a really great piece about schizophrenia that I read:

> In 2007, they announced a startling discovery. Stevens was trying to identify the proteins that recognized and eliminated neuronal synapses during visual development. “The strangest finding was that a protein that usually tags and removes pieces of dead cells, bacterial remnants, or cellular debris was also being reworked to tag and remove the synapses,” she said. Mice designed to lack tagging proteins—called complement proteins—had problems both in clearing cellular debris and in tagging and pruning their synapses.

> The Stevens and Barres study, published in the journal Cell in 2007, documented one of the most arresting instances of repurposing in biology: a protein designed to ticket germs and junk for destruction had been co-opted by the nervous system to ticket synapses for destruction. “It reinforces an old intuition,” my psychiatrist friend Hans, in Boston, told me. “The secret of learning is the systematic elimination of excess. We grow, mostly, by dying.”

https://www.newyorker.com/magazine/2016/03/28/the-genetics-o...

dwighttk
Does Hare Brain Tortoise Mind talk about the same things that Thinking, Fast and Slow calls system one and two?
corysama
I've not read Thinking Fast and Slow. But, I'm convinced Malcolm Gladwell read Hare Brain, replaced most of the research stories with funny anecdotes and sold 1000x as many copies of Blink.
reallydude
Multiple Intelligences Theory

https://en.wikipedia.org/wiki/Theory_of_multiple_intelligenc...

to which I subscribe, in a form.

keyle
Seems overly simplistic to me, I mean, one of us.
_Nat_
I think that Wikipedia article is about a different idea than the parent video.

The parent video is about the idea that an "individual" human mind can be described as being composed of subordinate minds. In this case, left-side vs. right-side.

The Wikipedia article is about the idea that there's no single metric by which we can judge human intelligence. This is, it's theoretically impossible to have any score, like IQ, that cleanly qualifies how smart people are relative to one another.

solipsism
Common human behavior is a lot more schizophrenic than any of us are comfortable with understanding.

How presumptive. Speak for yourself.

akvadrako
Indeed. I basically consider myself a corporation, with the conscious part playing the role of elected CEO.
AnIdiotOnTheNet
I think that's wishful thinking, actually. We like to believe there's a singular being in charge that we can label 'self', but I don't buy it. It seems to me that our minds operate more like a society or, at a higher abstraction, a committee, and it only seems like there's a singular entity in charge because the rationalization portion of our brain does its thing after decisions are made, making it seem as though there were a singular will determining our behavior.
mpa000
Like Minsky, who I've been waiting to be referenced in this subject but haven't seen yet:

https://en.wikipedia.org/wiki/Society_of_Mind

Waterluvian
I'll check out those titles, but put simply, are you referring to how I talk to myself in many voices in the shower, having a narrative about a problem I'm picking away at?
corysama
TLDR of HBTM is that there is a nonverbal, background thread of consciousness in your mind. It has the advantage of a larger working set (short term memory) compared to the verbal, foreground thread. Therefore it can more easily integrate more complicated observations over time than your foreground thought process.

It has the disadvantage that it is non-verbal and does not work quickly, on command or under pressure. You need to give it time to work and you need a quiet, non-focused environment for it to bubble up it's conclusions. Basically, you need to study as much as you can, then go for quiet walks where you relax and don't think about the problem.

It also has the disadvantage that, because your foreground process did not do the work to understand the problem (it just got a cliff notes answer), if the problem changes, your foreground process won't be in a good position to re-integrate the knowledge it didn't work through in order to deal with the changed problem.

dkersten
Rich Hickey’s talk on “Hammock driven development” talks about this too and the idea of HDD is to load the information into your mind and then... wait. Relax. Allow your subconscious mind to process it and make connections between things. Then, after an amount of time (how long and how many times you repeat this depending on the complexity of the thing and whether you feel like you have some insight yet or not) you consciously think about it again. Hence “hammock driven development”: think about your problem to load it in, then chill in a hammock for a bit.
sn41
There's a related phenomenon that I've experienced. Some of my best insights into problems have come to me when I was either very tired, drowsy, or slightly ill - like running a mild temperature. I wonder whether this is because the condition knocks out the foreground process, while not being drastic enough to knock you out fully.
knome
Sounds a lot like the gods in "Origin of Consciousness". Occurs as well, that for those that have seen the MBTI and Jungian stuff, that the introvert/extrovert duality they posit could be described as a tortoise/talker-affinity.
war1025
Hmmm. That pretty well explains how I've solved problems my whole life. Interesting. Will have to look into the book.
Waterluvian
Fascinating. Thank you.
corysama
btw: Your shower routine sounds like http://wiki.c2.com/?RubberDucking

The act of explaining a problem verbally to someone else forces you to be explicit about details that you gloss over when you think about the problem internally. The fun part is that you don't actually need a real person to explain to. Just going through the motions and explaining out loud to no one (or to a toy) is nearly as effective.

hyperpallium
I've used this for a long time. Observations:

- explains "prayer": talk it over with your God, leave it in God's hands, you get an answer.

- may have gteater survival value than the chatter we think of as "consciousness", and may be the actual intelligence that we're famous for.

dmitryminkovsky
Hare vs tortoise thinking is basically why I built Pony [0] an email service that sends and receives once a day. I find that time is critical for cognition, processing, basic reflection. Without the passing of time for me it’s really difficult to communicate at anything but the most basic level. Pony has let me tap into my tortoise brain for corresponding with people.

[0] https://www.pony.gg

sago
It seems rather intuitive to me.

Our brain is composed of neurons. Different subsets seem to have more or less specialised functions. Any subset can be seen as it own 'thinker'. We think of them as larger units based mostly on the amount of communication / how independently they can function.

Sometimes it is helpful to think of our mind as been made of many smaller 'thinkers'. Though there is no crisp boundary, every neuron is its own individual, at one extreme.

And I think it is sensible to speak of groupthink as a mind, with thinkers contributed by lots of people. So at the other extreme all is one super mind.

I think it can be useful to think of 'god' that way (as in the will of god, the desires of god, the thoughts of god), as much as a corporation, a culture, a nation. Though I admit you have to take care not to get carried away with the implications and end up mired in sloppy reasoning.

It is also not surprising that, because axon connections are many orders of magnitude more efficient than language, the most useful grouping is at the level of an individual.

Simon_says
> I think it can be useful to think of 'god' that way (as in the will of god, the desires of god, the thoughts of god), as much as a corporation, a culture, a nation.

That does not sound useful in the slightest.

sago
Do you mean 'god' as a synonym of theistic-religion groupthink? The idea of religious groupthink? Or the idea of groupthink in any context?
goodmachine
Bold move to mention 'god' on HN. I think the analogy is striking (therefore at least rhetorically useful) in the sense that it challenges the idea of ourselves merely ending where our bodies do.

Socialisation and attendant technologies suggest otherwise: there's plenty of 'me' which is opaque to me, of me that precedes me, of me that derived from other minds. 'I' may even reside briefly in other minds, such as (trivially) in the form of this comment.

The more we look at how individuals are structured from somatic to social levels, the less convincing the notion of individuality becomes.

sago
Probably also a dumb move, since it was incidental to my point, and probably skips a crucial argument step. Oh well.

I definitely agree with your last sentence. And this can be as simple as the idea, often observed, that someone 'lives on' in the minds of their loved ones after death. For me that is entirely non supernatural or mystical. As you say (and nicely phrased) our identity is a function of everything from the somatic to the social level.

ZeroFries
This works to some extent, but does not account for consciousness. A mind, at the very least a moment of experience, is a coherent whole. Your left and right visual fields are bound together. Thinking of neurons as entirely discrete units makes the binding problem insoluble.
theWheez
This question is considered in Sam Harris' Waking Up. Although I don't know how well Sam Harris is received here on HN, I finished it last night and thought it very thought provoking, especially when considering this relationship between the physical brain and our resulting subjective conscious experience.
sago
> This works to some extent, but does not account for consciousness.

True, although consciousness itself is rather poorly defined. There are also other related issues like qualia. But I'm not sure it needs to 'account' for those things. To observe that there are certain mental phenomena that are evident at different scales.

> A mind, at the very least a moment of experience, is a coherent whole.

That rather assumes your conclusion. In the example of a divided brain, a stimuli may be presented to only half the brain. How would one know whether one's experience of 'coherent whole'ness was accurate?

> Thinking of neurons as entirely discrete units makes the binding problem insoluble.

No more than thinking of base pairs in your DNA as discrete units makes higher order phylogenesis insoluble. To recognise that discrete units are simple does not mean that large aggregates of them cannot display fundamentally different dynamics.

plainOldText
Iain McGilchrist discusses at length the two-sided brain in his book The Master and His Emissary: The Divided Brain and the Making of the Western World [1]

Fun fact: He wrote the book over a period of 20 years.

[1] https://www.amazon.com/gp/aw/d/0300245920

pkghost
I read the first half of this book about eight years ago and haven't stopped noticing the same story in different places. It shows up in meditation frameworks (Chuladasa's attention/awareness) to Jungian psychology (anima/animus), in Jill Bolte Taylor's story "My Stroke of Insight", and many more. Here's a list of my favorites: https://www.notion.so/cameronboehmer/de3eb3e0a9524b6989962c4...
newnewpdro
I suspect we have a variable number of supplemental threads of execution serving the primary one we live on.

Recalling distant memories asynchronously after struggling to remember anything about it sometimes feels very much like another person interrupting and delivering the information once it's found.

scarcely
But there's always an immediate trigger
newnewpdro
Sure, they're cooperating, for now :)
DoreenMichele
Memory is a weird beast with many variables. A few things I know:

1. It's state dependent.

Example: I had a tortured first pregnancy and the birth was awful. For years, I couldn't clearly remember it.

Then I had a lengthy medical crisis that involved constant, excruciating pain. Suddenly, I could clearly remember the birth of my first child.

2. It's context dependent.

For example, people frequently fail to identify individuals they know if they run into them someplace they wouldn't expect to see them. They may realize they know the person, but just can't place them. (I have experienced this.)

This is also the mechanism behind going to do a thing, forgetting what it is, remembering when you return to where you were.

3. Emotion is a form of memory.

People with strong affect can make snap decisions based on "gut feeling." People with low affect cannot make snap decisions. They lack the file that sums up all their pertinent experiences as either "I have good feeling about this" or "I have a bad feeling about this."

4. "Muscle memory"

Some people think better while active. This is your stereotypical Pacer.

If you keep a dream journal, it's easier to remember dreams if you keep a pen and notebook on the nightstand and make notes without getting up at all. It's best to stay in bed and try to not leave your sleep position. Dreams can sometimes be retrieved by returning to whatever position you were laying in while dreaming.

5. Some people think in pictures. Some in words. This effects memory storage.

For most people, conscious recall of memory corresponds to learning to speak. It apparently heels people catalog their memories so the files are accessible.

I have a son who thinks in pictures. At some point, it became clear he could access pre-verbal memories, but it was like listening to someone translate a thing into English.

We actually went through a period where he waited until everyone else was asleep, then he would share his memories with me. Translating them to words from pictures helped him more readily access them.

There's no doubt tons more stuff to know about memory. This is very off the cuff.

ilogik
Relevant CGP Grey: https://www.youtube.com/watch?v=wfYbgdo8e-8
ianwalter
See, even the brain is split into microservices (ducks).
callesgg
We don't have two brains but if you split the brain it will become two brains.

This feels like people playing with words to grab attention.

dmpanch
Idea of “decentralized” brain perfectly explained in Michael’s Gazzaniga book “Who's in Charge? Free Will and the Science of the Brain”. He’s the first guy who makes experiments on split brain and found decisions making center which works like telling and explaining machine. Recommend.
locusofself
His book “human” is also very good
HNLurker2
Reminds me of Willpower instinct book that has similar but with the hypothesis that the prefrontal cortex is the "executive in charge of" type of brain.
myprasanna
Does anyone know why the left vs right hand behaves the way it does at the end of the video? Left as an exercise for us?
pkghost
The left hemisphere encodes tool use. Its preference for this is so strong that even left-handed folks encode tool-use in the left hemisphere, which means that the round trip from hand to brain goes left hand -> right hemisphere (b/c each hemisphere controls the opposite side of the body) -> left hemisphere (tool circuits) -> right hemisphere -> left hand, which is waaay less efficient than right hand -> left hem -> right hand. (https://www.ted.com/talks/iain_mcgilchrist_the_divided_brain)

So, the left hand's failure to pantomime screwdriver use probably reflects the commissurotomy patient's right hemisphere's inability to access her left hemisphere's knowledge of tools. (That this only happens when eyes are closed probably means the right hemisphere just observed and copied the right hand's behavior when eyes were open.)

Had a fun chat with someone interested in this at a bar a few weeks ago who offered a theory that the best pro basketball players are right hand/right eye dominant or left hand/left eye dominant, and that anybody with mixed dominance just can't cut it. Apparently the military just wont take you as a pilot or sniper if you have mixed hand/eye dominance?

Calling it now: laterality is central to who we are, and is currently underappreciated—especially in AI research (though I'd be delighted to hear from AI folks who disagree!).

EDIT: lots

JBiserkov
Relevant XKCD: https://xkcd.com/2120/
nwatson
The video doesn't portray the left-vs-right correctly. As the person and screens are set up in the video, the left and right eye both experience the left and right images presented on either side of the point-of-fixation. However, the video portrays all information from left eye going to right brain, and all information from right eye going to the left brain ... that's not how it happens ...

... rather, the left-hemi-visual-field from both left- and right-eyes goes to the right brain, and the right-hemi-visual-field from both eyes goes to the left brain, as depicted in [1].

[1] http://fourier.eng.hmc.edu/e180/lectures/eye/node4.html

EDIT: grammar

pkghost
the graphics indeed failed to reflect the fact that each eye is split vertically into two fields of vision that go to separate brain hemispheres (the inner field going to the same-side hemisphere and the outer half going to the opposite), but the narration was accurate: focused on a point between two screens, the left hemisphere sees only the right screen, and visa versa.
xtagon
So it works the same whether you have one or both eyes open? That's intriguing
pygy_
Yes, and you lose a hemi-field in both eyes if you have a stroke in the visual cortex on one side of the brain.

Central vision is preserved though, because the fovea projects to both hemispheres.

vanderZwan
> Yes, and you lose a hemi-field in both eyes if you have a stroke in the visual cortex on one side of the brain.

In my case the aura of my migraines (that I thankfully only had during puberty) were limited to the left hemi-field. Which I guess suggests that the migraine was "centered" in the right brain hemisphere.

pygy_
Correct!
vanderZwan
Do we know anything about migraines based on their symptoms? As in, has there been any research where people with different migraine symptoms have been put in a scanner during the migraine to locate which parts of the brain display weird activity?
pygy_
The migraine aura is rather well understood, it is the result of cortical spreading depression, a phenomenon where a "wave" of brain hyperactivity spreads in as a ring on the surface of the cortex, leaving a hypo-active zone in the middle.

It is possible to trigger the phenomenon by hurting the brain (e.g. sprinkle acid on a rat's brain, WP has a neat video: https://en.wikipedia.org/wiki/Cortical_spreading_depression) so we suppose that it is a defense mechanism in humans too, but we're not sure what causes them.

I've done research on migraine, 10 years ago, but I haven't kept up with the field. There are hypotheses, but no known cause for the headaches and associated symptoms.

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