The Minds Of Conjoined Twins

TheMadFool

Conjoined Twins is a biological phenomenon in which identical twins fail to separate in utero and are born and live sharing some or most of their organs. The particular kind of conjoined twins that's relevant to this discussion is the one in which there are two heads and the rest of the body is shared in variable degrees between the two heads that are, in all instances of such occurrences, treated as two different people.

First, the conjoined twins are identical with respect to their DNA. In other words, there's no physical difference between the two. The organ that I'm particularly interested in in this regard is the brain. The brains of conjoined twins can't be said to be perfectly identical; after all DNA doesn't and probably can't code for the 3-dimensional location of each and every brain cell or any other cell in the body. However, if the exact placement of brain cells in space mattered, there should be wide variability in brain function. This hasn't been observed. In fact, despite what are probably extreme variations in the microarchitecture (the exact locations of brain cells in 3-dimensional space) of brains, there's very little variation in its function e.g. all of us sense and respond to the environment in near identical ways. This means that brain function has more to do with gross structure of the brain like the cerebrum, the cerebellum, the amygdala, the corpus callosum, etc. rather than fine structure like the exact location of brain cells. People's brains differ in fine structure and not gross structure and brain function is determined by the latter and not the former is the takeaway here.

As an analogy, take two Toyota cars of the same model. If the exact location of the atoms and molecules mattered to how they perform then we should see extreme variability in their performance, as much variability as there is in the location of particular atoms and molecules of the materials the cars are constructed of. This isn't true, implying that the cars' perfomances are determined by gross structure like the fuel pump, the pistons, etc. and not the fine structure like the 3-dimensional loci of each atom and molecule of the cars' components.

In essence, the two brains of conjoined twins are identical. That takes care of nature.

The conjoined twins that matter here are the ones that haven't been separated for one reason or another. These twins, because they're stuck to each other, share the same experiences - they're exposed to the same ideas and the same physical environment. In short they're nurtured in the exact same way. That takes care of nurture.

Since a person's unique mental identity, personality, is said to be determined by nature and nurture, conjoined twins, because their nature and nurture are identical, should develop identical personalities. This isn't the case, implying that their different minds, personalities, can't be explained by physicalism. Ergo, the mind isn't physical.

Outlander

because they're stuck to each other, share the same experiences — TheMadFool

Not really. Some favor the left side of their body, others favor the right side of their body. Also, perhaps one has a tiny defect or something. The responsible party is likely to treat one differently over the other, whether for better out of sympathy or worse out of.. who knows what. Maybe the responsible party is either biologically detrimented (poor hearing) or socially disciplined (stricter parent happened to be sitting on one side of the table) to respond differently depending on what side of the head the person hears what from more strongly.

There's an infinite list of scenarios where one twin on one side has slightly different experiences than the other.

Pfhorrest

Brains are chaotic physical systems, which means they are extremely sensitive to initial conditions, and rapidly diverge in their future behavior based on accumulations of tiny tiny differences in ongoing conditions. Two identical chaotic systems sitting right next to each other undergoing “the same” (to the limits of our measurements) experiences would be expected to diverge in their behavior, even if physicalism is true, even if determinism is true.

If determinism were false, conjoined twins could diverge even if all their experiences were EXACTLY the same, without undermining physicalism. And even if determinism is true, because the experiences of the two brains are ever so slightly different, and brains are chaotic, we would still expect divergent behavior between them anyway.

In the medium term, at least. We would still expect convergent long-term trends between conjoined twin just like we expect between ordinary twins, ordinary siblings, or just people living similar lives, for the same reason that we can predict climate more accurately than weather.

aporiap

↪TheMadFool

You are equivocating with the term 'function', using it here to mean what seems like a more generalized anatomical function [e.g. basal ganglia has x function, visual cortex has y function(s)], which is not directly relevant to talk about minds.

What's relevant to any physicalist notion of mind is the function of the microarchitecture, the numbers and strengths of synapses and how that impacts information processing. You are completely side-stepping this in your discussion which I am unsure why.

TheMadFool

There's an infinite list of scenarios where one twin on one side has slightly different experiences than the other. — Outlander

Brains are chaotic physical systems — Pfhorrest

How do you know this?

experiences of the two brains are ever so slightly different — Pfhorrest

To both of you

Granted that there'll be differences, very tiny differences in my humble opinion, between the experiences of each conjoined twin but what's striking, if we must now discuss degrees and not type in re to the experiences of conjoined twins, is the, what seems to me physically inexplicable, relatively enormous dissimilarities in personalities of such twins.

TheMadFool

You are equivocating with the term 'function', using it here to mean what seems like a more generalized anatomical function [e.g. basal ganglia has x function, visual cortex has y function(s)], which is not directly relevant to talk about minds.

What's relevant to any physicalist notion of mind is the function of the microarchitecture, the numbers and strengths of synapses and how that impacts information processing. You are completely side-stepping this in your discussion which I am unsure why. — aporiap

If the brain's fine structure determines brain function, we should observe a proportionate variability in the way brains operate. This isn't true.

Outlander

↪TheMadFool

Snowball effect. They can be tiny yet turn into something huge. Say they play a game or challenge where there are two choices, say right or left. One chooses one, the other chooses the other. One is seen as the winner, the other a fool. Or wrong, at least. Again, that could snowball.

180 Proof

↪Pfhorrest

:up:

Olivier5

In essence, the two brains of conjoined twins are identical — TheMadFool

Nope. In the previous lines you argued they aren't, that they differ in their 'fine structure'.

These twins, because they're stuck to each other, share the same experiences — TheMadFool

I imagine that if I had to share limbs with my brother, we would have fought even more than we did. There's a competitive element in people's relations, which has to be taken into account. Some twins want to differentiate themselves from their brother/sister.

Pfhorrest

Brains are chaotic physical systems — Pfhorrest

How do you know this? — TheMadFool

I'm not sure if you're questioning the "physical systems" part or the "chaotic" part. I'll admit that I'm not absolutely certain on the "chaotic" part, but given the ridiculous complexity of brains, that seems a safe bet.

Snowball effect. — Outlander

This is basically what "chaotic" means: prone to the snowball effect, or more usually, the butterfly effect. Tiny differences at one time amplify to enormous differences at later times.

Pop

↪TheMadFool

Excellent topic.

Theoretically their consciousness should be composed of DNA, experience, and point in space, so you wouldn't think there would be much difference. Suppose their names were Jack and Joe.
Jack would have the experience of living next to Joe, whilst Joe would have the experience of living next to Jack.
Its probably not the same experience, and they would probably want to differentiate.

TheMadFool

Snowball effect. — Outlander

There are two things to consider here:

1. The brains of conjoined twins are identical in gross structure in the sense both have cerebrums, cerebellums, amygdalas, corpus callosums, etc. As I explained in the OP, brain function isn't determined by fine structure like the positions of the neurons or the number of synapses. If it were there should be extreme variations in mental ability which hasn't been observed. Ergo, it must be that not only conjoined twins but all of us have physically identical brains insofar as function - thoughts - matters.

2. Conjoined twins share the same universe in terms of ideas and the physical environment.

Yet, conjoined twins have very different minds. different personalities.

Were it true that the brain experiences something like the snowball effect, there should be easily observable differences in the minds of different people. Au contraire, there are more similarities between minds of different people than there are dissimilarities. Explain that.

Nope. In the previous lines you argued they aren't, that they differ in their 'fine structure'. — Olivier5

I also explained that the differences are irrelevant to brain function.

Some twins want to differentiate themselves from their brother/sister. — Olivier5

Exactly my point. Physicalism can't explain this. Kindly read my reply to Outlander.

but given the ridiculous complexity of brains, that seems a safe bet. — Pfhorrest

I think not. The brain is, if you recall your high school biology, the organ that coordinates all the other organs - far removed from a chaotic system.

Outlander

which hasn't been observed. — TheMadFool

Honestly I'd consider a bet where if anyone who reads this or ever will who has actually met/known/or seen a conjoined twin in person wins/loses $100. For each. It's beyond rare. That's not really a standard for assumption.

Conjoined twins share the same universe in terms of ideas and the physical environment. — TheMadFool

How is that different from siblings in strict, if not unrealistic (yet plausible) environments?

Were it true that the brain experiences something like the snowball effect — TheMadFool

I'm confused here. There is no observable experience or phenomenon in human existence that doesn't involve.. the human brain. I mean. It's not some non-existent term I made up based on nothing.

Au contraire, there are more similarities between minds of different people than there are dissimilarities. Explain that. — TheMadFool

It's not that bizarre really. Say a few people share a dorm room with the same computer ie. operating system. It's the same base when opened fresh out of the box. Yet, through time, each becomes customized based on the preferences of the individual.

Olivier5

I also explained that the differences are irrelevant to brain function. — TheMadFool

I am sympathetic to the broad thrust of your argument but find this particular premise a bit shaky.

One could posit that the brains of two identical twins are more similar to one another than, say, the brains of two siblings or those of two people taken at random. I don't know whether it's a proven fact but it can reasonably be argued. But brains of identical twins are always different in their 'fine structure' of neuron connections as you say, and the brains of any two strangers (e.g. yours and mine) are generally indentical in terms of their 'large structures' (cerebrum etc.). So the 'large structure' argument works for any pair of brains, not just for twins. It doesn't really cut it here, it's not specific to any twins.

I would rather start with two hypothetically identical brains in the twins. That is, erase the irreducible 'fine structure' differences by making the whole thing a thought experiment: let's assume for the sake of the argument that the twins' brains are identical, so they share the same brain and the same environment.

In this manner one can introduce the inevitable competition between the two brothers (even though they share that competition too) as one of the possible factors of divergence in the twins' general character and attitude to life.

TheMadFool

Honestly I'd consider a bet where if anyone who reads this or ever will who has actually met/known/or seen a conjoined twin in person wins/loses $100. For each. It's beyond rare. That's not really a standard for assumption. — Outlander

All I can say as of this moment is that it's more than just a hunch. If the fine structure of the brain - the exact number, location, synaptic connections, of nuerons - mattered to how our brain functions there should be pro-rata variations in minds, minds being equated to brain function in physicalism. In fact, generic brain abilities like walking, grasping, talking, thinking, etc. would be impossible if they depended on the brain's fine structure and not on its gross structure which is identical not only for conjoined twins but for everybody.

How is that different from siblings in strict, if not unrealistic (yet plausible) environments? — Outlander

No different I must admit but so what? I chose conjoined twins to make my case because they're the closest we can get to two brains being physically identical and having similar experiences which, according to the physicalism and nature-nurture theory, should've caused conjoined twins to have similar, if not identical, minds.

I'm confused here. There is no observable experience or phenomenon in human existence that doesn't involve.. the human brain. I mean. It's not some non-existent term I made up based on nothing. — Outlander

Read above.

It's not that bizarre really. Say a few people share a dorm room with the same computer ie. operating system. It's the same base when opened fresh out of the box. Yet, through time, each becomes customized based on the preferences of the individual. — Outlander

Ok but customizing a computer can't be explained in terms of hardware. The mind taking on different characters can't be explained by changes in the brain.

So the 'large structure' argument works for any pair of brains, not just for twins. It doesn't really cut it here, it's not specific to any twins. — Olivier5

That works in my favor. I chose conjoined twins for the reasons that

1) if two brains can be said to be physically identical then it doesn't get more identical than conjoined twins

and

2) I needed to control for variations in experience (nurture) like exposure to different ideas and physical environments

Pfhorrest

The brain is, if you recall your high school biology, the organ that coordinates all the other organs - far removed from a chaotic system. — TheMadFool

I think you’re still not understanding the technical meaning of “chaos” being employed here:

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

Pop

The brain is, if you recall your high school biology, the organ that coordinates all the other organs - far removed from a chaotic system. — TheMadFool

A lot of that high school stuff is now very dated. When an organ is transplanted, the nerve supply can not be rejoined, but the organ nevertheless is able to function. So it can not be said that the brain is controlling it. The organ seems to know what to do and how.

No different I must admit but so what? I chose conjoined twins to make my case because they're the closest we can get to two brains being physically identical and having similar experiences which, according to the physicalism and nature-nurture theory, should've caused conjoined twins to have similar, if not identical, minds. — TheMadFool

I was very excited by your post, as what you posit would be a way to prove bodily feeling experienced by one is also felt by the other, but reliable information is scant. I can only find unreliable information.
The twins are conjoined in various different ways, and this results in various different outcomes. There are just not enough of them to come to any conclusions, I feel.

TheMadFool

think you’re still not understanding the technical meaning of “chaos” being employed here: — Pfhorrest

I understand chaos as the behavior of a system extremely sensitive to tiny differences in initial states.

My problem with this is whether chaos theory is applicable at all to brains? There are two forces acting on the brain, 1. ideas and 2. the physical environment.

I can accept that the physical environment (temperature, humidity, air pressure, etc.) can vary quantitatively in ways that chaos in brains becomes possible a la the classic butterfly effect. However, if the physical environment has such an effect on the mind, we should be seeing a clear gradation in mind-types (gradation in beliefs, attitudes, etc.) with latitude, temperature being the most well-defined variable in physical environment. What I'm saying is the minds of people living in hot places should be different from the minds of people living in cold places. I haven't come across any scientific study that makes such a claim. Perhaps something worth investigating.

Coming to ideas, the notion of small differences in initial states doesn't make sense because ideas aren't quantifiable like temperature or humidity or air pressure. It's nonsensical to say that one person was exposed to 1.002 of atheism and another person to 1.012 of atheism.

All in all, chaos theory doesn't seem applicable to mind and its environment.

A lot of that high school stuff is now very dated. When an organ is transplanted, the nerve supply can not be rejoined, but the organ nevertheless is able to function. So it can not be said that the brain is controlling it. The organ seems to know what to do and how. — Pop

Organ coordination is done not just through nerves. Hormones which trace their origins back to the brain are another control mechanism.

Pfhorrest

I can accept that the physical environment (temperature, humidity, air pressure, etc.) can vary quantitatively in ways that chaos in brains becomes possible a la the classic butterfly effect. However, if the physical environment has such an effect on the mind, we should be seeing a clear gradation in mind-types (gradation in beliefs, attitudes, etc.) with latitude, temperature being the most well-defined variable in physical environment. What I'm saying is the minds of people living in hot places should be different from the minds of people living in cold places. I haven't come across any scientific study that makes such a claim. Perhaps something worth investigating. — TheMadFool

You seem to be thinking of the brain as though it were a gas, with its processes predictably correlating with the things that you list (temperature, humidity, air pressure, etc). That has nothing to do with chaotic things like the butterfly effect; in fact such a correlation is contrary to them. The brain as a chaotic system would be one in which, say, a single sodium ion either does or does not make contact with a neuron because of some small physical difference, and then that neuron does or does not fire in accordance with that, and then all of the neurons that would fire in response to that one firing either do or do not fire in accordance with that, and then all the neurons that they would trigger to fire either do or do not in accordance with that, and pretty soon you've got a vastly different state of which neurons are firing, and so what the brain overall is doing, all because some trivial physical effect either did or didn't inhibit the motion of a single sodium ion.

TheMadFool

You seem to be thinking of the brain as though it were a gas, with its processes predictably correlating with the things that you list (temperature, humidity, air pressure, etc). That has nothing to do with chaotic things like the butterfly effect; in fact such a correlation is contrary to them. The brain as a chaotic system would be one in which, say, a single sodium ion either does or does not make contact with a neuron because of some small physical difference, and then that neuron does or does not fire in accordance with that, and then all of the neurons that would fire in response to that one firing either do or do not fire in accordance with that, and then all the neurons that they would trigger to fire either do or do not in accordance with that, and pretty soon you've got a vastly different state of which neurons are firing, and so what the brain overall is doing, all because some trivial physical effect either did or didn't inhibit the motion of a single sodium ion. — Pfhorrest

This still doesn't make sense. You mean to say that if someone were to introduce me to atheism/theism, my response to it depends on variations in sodium ion concentration and sodium channel activation. If this were true there should be more shades of these ideas then there actually are; after all at the molecular level of neurochemistry variations are continuous and exist over a wide range of concentrations and activations of sodium ions and ion channels. Basically, the limited output - variations in theism/atheism - doesn't square with the enormous input - variations at molecular levels.

Pfhorrest

You mean to say that if someone were to introduce me to atheism/theism, my response to it depends on variations in sodium ion concentration and sodium channel activation — TheMadFool

Probably not in that direct a fashion. But your response to the ideas of atheism or theism would depend heavily on your other life experiences, which would depend on previous life experiences, where those life experiences can be influenced tremendously by tiny choices you make, tiny variations in your mood, things that aren't such a clear black or white conscious choice but more something that you wouldn't be able to clearly state why you did one thing instead of another, you just felt like one more than the other; but those choices ended up giving you a different experience in your life, and that different experience in your life changed how you would react to the ideas of theism and atheism. And those tiny subconscious states of mind that can send you down one life path instead of another can be influenced by small changes in neurochemistry.

Olivier5

if two brains can be said to be physically identical then it doesn't get more identical than conjoined twins — TheMadFool

Fair enough but it's still a mind experiment, so there is no harm in assuming the two brains absolutely identical in every way at start.

TheMadFool

influenced tremendously by tiny choices you make, tiny variations in your mood — Pfhorrest

You mean to say that beliefs are dependent on one's mood. This turns philosophy on its head. Can you elaborate on this point.

Olivier5

↪Pfhorrest

The brain is highly structured, and not chaotic in the sense that people are predictable to a fair degree. They sleep at certain times, they have certain habits such as tea or coffee, certain opinions that are so we'll rooted that no amount of conversation can change them, etc. This is not typical of a chaotic system. Too predictable.

aporiap

↪TheMadFool

If the brain's fine structure determines brain function, we should observe a proportionate variability in the way brains operate. This isn't true. — TheMadFool

Please explain specifically what you mean by function and operate. Like I said, if you mean generalized function of a specific brain tissue like olfactory bulb, amygdala or visual cortex, then this is just a strawman because these things are not relevant-- i.e. it would be like saying the hard disk of computer A functions the same as computer B [i.e. they store memory], thus
the variability of the microstructure [i.e. the orientation of magnets on the hard disk, which is the physical representation of the computer memory] doesn't matter for what the hard disk does. But it does matter.

If by function, you mean the specific output of a person's brain tissue, then the function does vary considerably. The output of your visual cortex when viewing a tasty, gushing burger is completely different to the output of my visual cortex when viewing a chair. The output of my amygdala after seeing a picture of Natalie Portman is not the same as the output of my amygdala after discovering a spider crawling up my arm. And those outputs are different in other people.

Pfhorrest

You mean to say that beliefs are dependent on one's mood. — TheMadFool

Not directly. But they're dependent on previous beliefs, which are dependent on previous experiences, which are dependent on previous choices, which are dependent on previous moods. It's not as simple as you want to make it out, so as to easily refute it.

The brain is highly structured, and not chaotic in the sense that people are predictable to a fair degree. They sleep at certain times, they have certain habits such as tea or coffee, certain opinions that are so we'll rooted that no amount of conversation can change them, etc. This is not typical of a chaotic system. Too predictable. — Olivier5

Long-term climate trends are also highly predictable and regular, but weather is very chaotic. I mentioned this comparison in my first post in this thread.

Olivier5

↪Pfhorrest

Okay, good point that chaos and regularities are not mutually exclusive. And I agree that there is some degree of chaos in my own mind at least - a necessary feature for creativity me think. But there must also be strong integration and regulation mechanisms at play, because in the final analysis people tend to be predictable. At least to a degree. They have their strengths and weaknesses for instance.

I believe that consciousness is one such mechanism working toward coherence. It's an integrative mechanism, like a mental dashboard, that prepares for action. Action is singular by nature:you can't flee and fight at the same time, you can't make two chess moves at the same time. You must chose one way or the other (exclusive 'or') often under severe time constraints.

Such integration of disparate information and thoughts into a coherent framework for data-based decision making must be an energy-hungry and tiring process, which would explain sleep as a universal phenomenon among superior animals. Sleep is when our mind disintegrates a bit.

In this view, schizophrenia would be a mental integration failure.

TheMadFool

Please explain specifically what you mean by function and operate. Like I said, if you mean generalized function of a specific brain tissue like olfactory bulb, amygdala or visual cortex, then this is just a strawman because these things are not relevant-- i.e. it would be like saying the hard disk of computer A functions the same as computer B [i.e. they store memory], thus
the variability of the microstructure [i.e. the orientation of magnets on the hard disk, which is the physical representation of the computer memory] doesn't matter for what the hard disk does. But it does matter. — aporiap

Take your brain and mine for comparison. It's quite obvious that they differ in terms of actual number of neurons, the number and complexity of synapses, the loci of brain cells, etc. Yet, we can both talk, walk, eat, think in, factoring these variations, extremely similar ways. Had these variations any effect on the way our brains operate/function, it would show in the areas of brain function I mentioned. We wouldn't have generic abilities like walking, talking, eating, thinking, etc.

If by function, you mean the specific output of a person's brain tissue, then the function does vary considerably. The output of your visual cortex when viewing a tasty, gushing burger is completely different to the output of my visual cortex when viewing a chair. The output of my amygdala after seeing a picture of Natalie Portman is not the same as the output of my amygdala after discovering a spider crawling up my arm. And those outputs are different in other people. — aporiap

You're comparing apples to oranges. Of course our mental states would differ between a delicious burger and a spider crawling up our arm. However, if both of us were exposed to the same stimulus, we would experience comparable mental states. If my mouth waters in gustatory anticipation when I see a burger, it's highly unlikely that you would retch and vomit in disgust. This similarity in responses to the physical environment and ideas bespeak the reality of what I've referred to as generic brain functions, something that would be impossible if the fine structure of brains mattered to mental states.

Not directly. But they're dependent on previous beliefs, which are dependent on previous experiences, which are dependent on previous choices, which are dependent on previous moods. It's not as simple as you want to make it out, so as to easily refute it. — Pfhorrest

So, is it fair to say that the belief your espousing in this thread is ultimately mood-based? Why are you trying to argue then?

Pfhorrest

So, is it fair to say that the belief your espousing in this thread is ultimately mood-based? Why are you trying to argue then? — TheMadFool

Moods are just an example of a subtle non-rational brain process that can go on to influence your life in the future. They’re not at all integral to the point I’m making.

For another example, say you’re on a walk one day and at a fork in the road you have to go left or right, without any real reason for either. One of those choices will lead you to meet a person who will become a short-time acquaintance of yours through whom you will meet someone else who will introduce you to a new circle of friends among whom you will meet your future spouse with whom you will have many deep conversations that will heavily influence your opinions on things like theism or atheism. If you turned the other way on that walk, your future state of mind would have turned out completely differently. And whether you felt inclined to turn left or right is the kind of thing that could be influenced by tiny physical differences, or more likely built up to by an accumulation of consequences of tiny physical differences in the same way that your future beliefs were built up to by an accumulation of differences based on whether you turned left or right.

TheMadFool

Moods are just an example of a subtle non-rational brain process that can go on to influence your life in the future. They’re not at all integral to the point I’m making. — Pfhorrest

You lost me. I'm under the impression that you're talking about moods to prove that beliefs depend on them in a very important way, to wit that they're the tiny, almost imperceptible, differences that are part of your chaos theory of mind.

For another example, say you’re on a walk one day and at a fork in the road you have to go left or right, without any real reason for either. One of those choices will lead you to meet a person who will become a short-time acquaintance of yours through whom you will meet someone else who will introduce you to a new circle of friends among whom you will meet your future spouse with whom you will have many deep conversations that will heavily influence your opinions on things like theism or atheism. If you turned the other way on that walk, your future state of mind would have turned out completely differently. And whether you felt inclined to turn left or right is the kind of thing that could be influenced by tiny physical differences, or more likely built up to by an accumulation of consequences of tiny physical differences in the same way that your future beliefs were built up to by an accumulation of differences based on whether you turned left or right. — Pfhorrest

I understand the significance of differences in experience for how we turn out to be down the road but conjoined twins don't have that luxury. They're stuck to each other, remember?

Pfhorrest

I understand the significance of differences in experience for how we turn out to be down the road but conjoined twins don't have that luxury. They're stuck to each other, remember? — TheMadFool

Yeah, the left-or-right thing isn’t meant to apply to the twins, it’s just a clearer example of the butterfly effect. A tiny insignificance change can snowball into a large difference through unpredictable complications. Likewise, tiny differences in the two twins’ brains compound over time into larger different between their brain-states. We would still expect a lot of similarities of their brain states, because of their shared experience and genetics, but this allows for enough differences to explaining why they aren’t exactly the same person despite those similarities.

The Minds Of Conjoined Twins

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