About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Monday, July 26, 2010

Mr. Potato Head and Philosophy

By Julia Galef

If you listen to the Rationally Speaking podcast, you may remember Massimo and me mentioning the Pop Culture And Philosophy series, which is famous for expounding on everything from The Matrix as a case study in simulated universes, to theological paradoxes raised by Homer Simpson's cravings for a burrito. 
Well, a few weeks ago I saw the excellent Toy Story 3 movie, and my first thought as the credits began to roll (well, unless [sniffle] counts as a thought) was: "Those were some complex musings on personal identity. Somebody should really write a 'Toy Story 3 and Philosophy.’” My second thought was: “Hey, I'm somebody...” And indeed, I am. So here we go:
Toy Story 3 and Philosophy, part I: Mr. Potato Head

Perhaps the most hilariously surreal moment in the movie occurs when Mr. Potato Head disassembles himself. He has been imprisoned in a box, and the one hole in the box is nowhere near large enough for him to squeeze out through. So he pops his plastic eyes, nose, ears, arms and feet out of his potato-body (head?), tossing them through the hole so they land in a heap on the ground outside. And just as you're wondering, “What good did that do him?” each body part stirs itself and they all scurry away. They're traveling as a group, but a group of distinct individuals; each part moves independently, seemingly possessed of a mind of its own.

“Now wait a minute,” you might object. “Just because the various body parts are moving independently of each other, that doesn't necessarily mean they have separate minds. Maybe Mr. Potato Head still has the one mind, which is somehow able to control his body parts from afar.”

Well, Hypothetical-You, that's an excellent point! But it's provably false, even within the fantastical and unspecified logic of the Toy Story universe. If you pay close attention, you'll notice a subtle clue that rebuts your one-mind hypothesis: A few scenes later, the various body parts have embedded themselves into a flour tortilla (it's a long story; just watch the movie, ok?), which serves as an adequate, if floppy, substitute body for them. 
Unfortunately, a passing pigeon takes an interest in the tortilla and pecks at it until it falls apart. One shred of tortilla, containing an eye and an arm, sits up and looks around. Then, with the eye spotting a potential threat approaching, the arm nudges another nearby shred of tortilla (containing a leg) to alert it to the situation. 
Do you see where I'm going with this? The fact that this physical communication between Mr. Potato Head's body parts was necessary reveals that the separate parts aren't being controlled centrally by a single mind. The only conclusion left for us to draw is that each part is controlled by an autonomous mind. Which then raises the question: when Mr. Potato Head's parts are all assembled as per usual in his potato-body, does he have one mind, or does he consist of a complex collaboration between independent minds?

And this is — weirdly, astonishingly — a question that applies to our own minds as well. It's pretty well known that the two hemispheres of a human brain each have different functions, and that they communicate constantly via the corpus callosum which connects them. At first blush, this fact doesn't seem to endanger our belief that we each have a single, distinct mind. But what if you sever contact between the two hemispheres?

This has happened to some people. Called “split-brain patients,” they seem to function normally in most circumstances. But the oddness of their condition manifests when you give a piece of information to only one of their hemispheres, which is then unable to communicate the information to the other hemisphere. How do you do this? By giving the information to only one eye, for example, or to only one hand — sensory inputs from the right eye and hand go only to the left hemisphere, and from the left eye and hand only to the right hemisphere. 
This produces some very striking results, like this one described in Derek Parfit's Reasons and Persons:

One of these people is shown a wide screen, whose left half is red and right half is blue. On each half in a darker shade are the words, 'How many colours do you see?' With both hands the person writes, 'Only one'. The words are now changed to read: 'Which is the only colour that you can see?' With one of his hands the person writes 'Red', with the other he writes 'Blue'.
… Or this one, from Thomas Nagel's “Brain Bisection and the Unity of Consciousness”:
One particularly poignant example of conflict between the hemispheres is as follows. A pipe is placed out of sight in the patient's left hand, and he is then asked to write with his left hand what he was holding. Very laboriously and heavily, the left hand writes the letters P and I. Then suddenly the writing speeds up and becomes lighter, the I is converted to an E, and the word is completed as PENCIL. Evidently the left hemisphere has made a guess based on the appearance of the first two letters, and has interfered, with ipsilatral control. But then the right hemisphere takes over control of the hand again, heavily crosses out the letters ENCIL, and draws a crude picture of a pipe.

And just as with Mr. Potato Head, witnessing our brains' component parts make decisions independently when they are no longer connected raises the question of how exactly we should view them when they are connected. Our intuitive sense that a normal (non split-brain) person has one single mind becomes problematic, because now we know that if we cut the corpus callosum, the person appears to have two minds, operating simultaneously and independently. So did another mind pop into existence when the corpus callosum was cut? And if so, what happened to the original mind — is it now located in the left, the right, or neither hemisphere? The questions raised by this explanation are arguably even more mystifying than the original mystery we were trying to explain.
So the only interpretation which doesn’t seem to suffer from internal contradictions is that the whole idea of distinct, countable minds, no matter how intuitive and self-evident it may seem, is in fact an illusion. And this is the conclusion endorsed by the handful of neuroscience friends I’ve cornered and asked about this, yet it’s so staggeringly counterintuitive that it seems to demand the invention of some new, stronger version of the word "counterintuitive.”

I wish I could comment more intelligently on this conclusion, but so far I haven’t managed to muster anything more coherent than “!!!?!!??!” If you want to read more about the split-brain phenomenon and what we should make of it, I'd recommend Derek Parfit (Reasons and Persons, Part III) and Thomas Nagel ("Brain Bisection and the Unity of Consciousness," in his Mortal Questions). And if you figure it out, come back and explain it to me.

Coming up in Part II: Lots-o-Huggin' Bear and Philosophy. 


  1. In case you haven't seen it, here is a TED talk by Ramachandran on brain damage and the mind . In his third example (concerning a phantom limb) the patient and doctor (the mind, if you will) literally have to trick the brain into believing something. Nothing happens until that unconscious process is completed.

  2. We're going to have to abandon the concept of the mind as a unity, a single, a one. What neuroscience has been able to show is that each of us is, in fact, a multitude. The human brain is composed of 10^11 neurons communicating with each other across 10^14 synapses. (http://en.wikipedia.org/wiki/Neuron) The mind is the song they sing to each other.

    By this point we understand the brain on the largest scales and smallest scales pretty well. We know what regions of the brain handle which tasks, and which sensory and motor organs those brain regions are wired to. On the small side, we have a reasonable working model of a neuron, and how ion flows create action potentials and neurotransmitters jump the gap at the synapse.

    But the middle scales are a task that is too big and, paradoxically, too small. How do middle-size networks of thousands or millions of neurons, which may be spread out throughout the brain or be relatively confined to a small area, coordinate to spark a thought, or form a memory, or control a muscle?

    Regardless of the shape the answer to that question takes, the fact remains that the behavior of these networks is driven by single neurons obeying local rules and responding to the local environment.

    I am not a one. I am a one hundred billion.

  3. I'm of two minds about this...
    Just kidding. This puzzle sounds a lot like snapping a stick in half and ending up with two sticks. Did a new stick pop into existence, and if so, what happened to the original stick?

    I bet split-brain patients think out-loud a lot to keep their two minds in sync.

  4. @Max -- I am very sympathetic to the point of view you stated, that it's essentially an empty question whether we call it "one new mind popping into existence" or "two new minds, each continuous with the original mind", etc. We know all the facts about what happened, so we're just arguing about labeling now, right? This is the kind of argument I find myself making all the time, in fact. (And it's Parfit's argument in this case, too.)

    But if you accept that argument here then you have to acknowledge that (1) our intuition that we have "one" mind in our normal state is wrong, and (2) that it is meaningless to ask whether "I" will continue to exist when you split my hemispheres. And even though I accept the logic of your and Parfit's position here, both (1) and (2) feel utterly unlike empty questions to me. They *feel* like they matter a lot and are not just a matter of definitions, from my perspective as the "I" in question.

    So now I am just trying to figure out how to reconcile these very strong intuitions I have, and the logic.

  5. uh, oh, sounds to me like Julia is dangerously being fascinated by philosophy...

  6. Ha, actually Massimo, I haven't told you this yet, but I've softened my position slightly on philosophy. For the last couple of months I've been compiling a list of meaningful, non-obvious questions that either (1) have been answered by philosophers in a way that I think is soundly-reasoned, or (2) have not been answered yet to my satisfaction, but that I think are plausibly the domain of philosophy (rather than an empirical science as I often maintain).
    This question would be on list #2.

    I'm sure my lists are still way shorter than yours, but they do at least exist!

  7. Welcome to the Dark Side... On a more serious note, of course, remember that my position is that there are scientific questions and philosophical questions, but that *both* are informed by the other's perspective. That's what I call sci-phi.

  8. Do split-brain patients report a qualitative change in their experience of consciousness? If you ask these people's left hemispheres how their conscious experience is different than it was before the c. callosum was severed, what do they say?

  9. Julia,

    When the two hemispheres are connected, they behave as one, like the sticks. That's why it's hard to draw two different pictures with two hands at the same time. Doesn't that reconcile the intuitions?

  10. "My Stroke of Insight" by Jill Bolte Taylor is an interesting book by a brain anatomist who has a stroke and gets a first hand experience of the subjective functions of the hemispheres. While I am not happy with the metaphysical and mystical conclusions she draws from her ordeal, I think it's worth reading. I haven't seen her TED talk yet.

    What struck me about the the split brain experiments Nagel cited (way back when) is that the linguistic part of the mind seems compelled to explain things that it can't possibly explain. It is willing to guess in a desperate attempt to maintain at least the illusion of coherence. Another experiment he recounts has a naked women shown to the right hemisphere. The left side is aware of the resulting smile, but comes up with a bogus explanation "you have a funny machine." Similarly with early stages of Alzheimer's it's common for people to mask and compensate for their symptoms. From a skeptical/rationalism POV I think it's important to see how the illusion of one mind is not the only illusion our brains seem to be committed to maintaining. Add to the list, competence, consistency etc. Brains seem to be good at taking creding and faking a lot of things.

  11. OneDayMore,

    After the left hemisphere gave the bogus explanation, did the right hemisphere do a *facepalm* with the left hand or something to that effect? More generally, is the right hemisphere bummed that it can't speak? Apparently, it can read questions and point to answers. Can it learn sign language?

  12. Max I'm enjoying but not understanding your sarcasm. I am personally quite suspicious of a lot of the "right/left hemisphere" talk, especially as it shows up in popular culture in the form of a very small zodiac.

    Another way to look at this topic is to question what I call the skull dichotomy. We are, after all, entire organisms with our brains being only part of our nervous system. So while we have an obvious bias for the brain, it doesn't really make sense to say that our "mind" and "self" only reside there (obviously the bulk of it does, but still...). So whatever conclusions we can draw from a brain with a severed corpus callosum shouldn't be fundamentally different than the types of conclusions we would draw from someone with a severed spinal chord. It shouldn't seem any more odd that speech tends to be on the left side of the brain, than walking tends to be bellow the neck. And when severed, the brain still tries to communicate with the legs and may even have a phantom experience of them. If you tickle the toes and the sensation travels to the brain through a tertiary route causing a smile and the person invents a reason for the smile, it would seem (except for my point about taking credit for no good reason) not quite so significant. Why, though? Because we are loath to call the neurological events in the foot "mind." But why? No good reason but the skull dichotomy.

    I think the skull dichotomy is behind the annoying thought experiment of "Mary's Room." A genius child who knows everything about the biology of color, but who has never experienced the seeing of it, is like a genius child who knows everything about the biology of a broken leg but who has never experienced the breaking of it. It's only the skull dichotomy that makes the difference between the first two seem more significant than the second two. We understand seeing in one part of the brain, but experience it in another.

    So yeah, Max, a stick broken in two. Different parts of the brain have different functions, it shouldn't be such a big deal.

  13. Our intuitive sense that a normal (non split-brain) person has one single mind becomes problematic, because now we know that if we cut the corpus callosum, the person appears to have two minds, operating simultaneously and independently. So did another mind pop into existence when the corpus callosum was cut? And if so, what happened to the original mind — is it now located in the left, the right, or neither hemisphere?

    I may of course be missing something, but I don't see the problem in viewing the mind as made up of many communicating components. The really strange thing would be if you could cut away parts of the brain to finally locate 'the mind' in the last remaining part.

  14. Great topic.

    OneDayMore makes some interesting points I'll focus on more below, but do I think that brain-centrism is justified by people like Stephen Hawking and phenomena like dreaming and hallucinations.

    In the original post, Masimo said:
    Our intuitive sense that a normal (non split-brain) person has one single mind becomes problematic
    I would resist the claim that these results throw much doubt on the view that we normally have a single mind. Someone could just as easily argue that the results merely show that cutting a brain in half (and putting the subject in rather contrived experimental conditions) can disrupt this normal unity of the person.

    OneDayMore points out that perhaps we shouldn't be surprised as we already knew that the brain processes information in multiple parallel processing streams (different modalities, submodalities, etc). If the data were merely something like a stroke on the left causing paralysis on the right, we wouldn't be surprised, but the phenomena are much more high-level that that. In normal people these tasks depend on conscious processing. Even stranger, we have what seems to be two wills pushing toward different goals.

    That the hemispheres respond with different answers when asked what color they see is quite amazing. This suggests that each hemisphere is sufficient to support conscious experience.

    Why is that interesting. For one, it would shed doubt on many theories of consciousness, such as those in which consciousness requires language (Jaynes' bicameral mind theory). I supposed someone could say that one of the hemispheres is simply responding with the correct answer but is not basing it on an actual experience of the color mentioned (some kind of confabulation theory): in that case one of the hemispheres would be an instantiation of the philosopher's zombie. Either way, cool stuff.

    It's such claims about color experiences that are most counterintuitive of all (I'm assuming this is a robust phenomenon that has been replicated, so please correct me if I'm wrong). When I experience red, I think it is me having that experience. Not you. Not my wife. I am having this experience, and that "I" is usually taken in the singular. It's not that "we" are experiencing red. That's not phenomenologically how it seems. It seems there is indeed one person here to which the contents of experience belong.

    When your brain is cut in half, it may be that this typical unity can be disrupted (though see below). I don't think this shows that the "unity intuition" is necessarily wrong, as we could be creating two separate unified consciousnesses in a single brain.

    Note one thing to keep in mind is that in normal circumstances the split-brain patients are fine. It takes a great deal of experimental effort to generate these mind-cracking effects. Normally, each eye sends information to both hemispheres (it isn't enough to give the information to only one eye, for example, just to make a picky anatomical point with the original post (see the anatomy here). Also, they continue to dart their eyes around integrating information from the scene. So it's not like these people run about fighting themselves in real life. Getting these effects requires a great deal of effort from the experimenters.

    Thinking about this in the context of Dennett's Where am I thought experiment is pretty fun stuff. How far could we take that, how different can the two hemisphere's experiences be? What if each was hooked up to a different body, could we induce them to duke it out? Just how disparate could we make their worlds? Could one be in Timbucktu and the other in Guantanamo Bay? Where are we?

  15. Oops sorry attributed quotes to Massimo rather than the author of the post, Julia.

    Julia, I'd be curious to see what problems you think philosophy has solved in the past 50 years (e.g., since Russell and Whitehead). One sure way to get a roomful of academic philosophers emotional is to ask them what results philosophy has produced in the last 50 years. You will rarely witness a higher degree of professsional insecurity, especially if they know you are a scientist. :)

  16. I've accepted the idea that there is no unitary self of the sort we intuitively believe in. But I still have some difficulty reconciling this with the apparent unity of the "Cartesian theatre" (as Dennett calls it) through which we view the world. To call this unity an illusion seems like question-begging. How can there be an illusion unless there is a unitary entity experiencing that illusion?

    ianpollock wrote: "Do split-brain patients report a qualitative change in their experience of consciousness?"

    I was wondering that too. I'd particularly like to know if there's any evidence for whether each half of the split brain has its own Cartesian theatre. In the red/blue experiment above, it seems like one half of the brain constructs an image of a red screen while the other constructs an image of a blue screen. But, if so, are those two different images both experienced in the same way that the Cartesian theatre is normally experienced, so there are two separate Cartesian theatres?

    I'd also like to know whether such experiments give different results depending on whether the brain was split recently or some time ago. Perhaps with time each half of the brain develops functions that were previously exclusive to the other half.

  17. "Far away, on the other side of our galaxy, there was a planet on which lived beings like ourselves--featherless bipeds who built houses and bombs, and wrote poems and computer programs. These beings did not know that they had minds. They had notions like "wanting to" and "intending to" and "believing that" and "feeling terrible" and "feeling marvelous." But they had no notion that these signified mental states."

    Ch. II, Persons without Minds, The Antipodeans, R. Rorty: Philosophy and the Mirror of Nature (1979)

    On the sci-phi issure, it seems to me, once again there were good philosophical reasons to reject the concept even before the evidence from neuroscience came about.

  18. "Far away, on the other side of our galaxy, there was a planet on which lived beings like ourselves--featherless bipeds who built houses and bombs, and wrote poems and computer programs. These beings did not know that they had minds. They had notions like "wanting to" and "intending to" and "believing that" and "feeling terrible" and "feeling marvelous." But they had no notion that these signified mental states."

    Ch. II, Persons without Minds, The Antipodeans, R. Rorty: Philosophy and the Mirror of Nature (1979)

    Sorry for the quote but I bring it here, firstly, because it's what Julia's philosophical story telling reminded me of, and secondly, to show, on the sci-phi issue, that once again there were good philosophical reasons to reject the concept even before the evidence from neuroscience came about. Of course the question is not completely settled and I find those discoveries quite fascinating.

  19. Actually, this is serious. Because the split-brain patient's left hemisphere is the one that speaks, the researcher may equate it with the patient and treat the right hemisphere as something less than a person. Meanwhile, it may be a second conscious person who can't speak. Ramachandran described a patient whose right hemisphere believes in God, and the left hemisphere doesn't.

  20. Somewhat tangential, but sensory inputs from each eye don't go separately to the contralateral side of the brain. Its much cooler than that, since the entire left visual field is processed by the right hemisphere and the entire right visual field by the left hemisphere. http://tinyurl.com/242se9n Patients with hemispatial neglect, in which one hemisphere's visual field processing has been damaged, completely ignore the affected side of the world (eg they might only eat the food on the left side of a plate).

  21. Julia, of all the Toy Story 3 plot elements that have deep philosophical implications, you are most impressed by Mr. potato head? Come on! Buzz can be switched into a Spanish mode! That, my friend, totally destroyed the unity of consciousness.

  22. Well, Max, the original stick has ceased-to-be, and two new sticks have come-to-be. Not come-to-be ex nihilo, but from the underlying substance of the original stick. Likewise for split minds and the original mind. Aristotle had it all figured out: see Aristotle on coming-to-be & passing-away (De generatione et corruptione). Or Aristotle on change.

  23. The slit-brain phenomenon does not appear to be too surprising to me. After all, we know that the structures of the two hemispheres are almost identical (despite some degree of lateralization). If split brain patients do not exhibit divided consciousness, that will be truly surprising. Suppose only the left hemisphere is "conscious", what does the left hemisphere have that the other half doesn't have? Not a lot.

  24. I love this subject, but i hate it... just joking :)
    As I see it, there are in fact three minds, and when severed, one stops to exist, much like orange is the third color, resulting from yellow and red mixed together. Split brain patients have two different minds, and sometimes very different, as a case from ramachandran where one side is an atheist and the other is religious, what happens when the body dies? On hemisphere goes to hell and the other to heaven? And the third "mind", where would he go? I think I just made more questions...

  25. "Toy Story 3" inspired the same response in me, only I went in a different direction:

    When Mrs. Potato Head loses her eye, which has rolled under the bed, she gains the ability to see at a distance. She does not, however, perceive herself to be under the bed. Rather, she perceives herself where her body is, only receiving visual input from Andy's room.

    When Mr. Potato Head transfers his various organs to the tortilla, his consciousness is no longer in the potato, but in the tortilla. This is true even when the tortilla is torn into pieces, and later, when his organs are transferred to a cucumber. Where his organs go, his essence goes; his body remains behind, inert and soulless.

    In what physical vessel is Potato Head identity contained?

    Imagine Mr. Potato Head transferring his organs, one at a time, to the tortilla. At what point does he cease to be Mr. Potato Head and become Mr. Tortilla Face? How many organs must be resituated before his consciousness is embodied not in the potato but in the tortilla, and which ones? (One eye, for instance, is clearly not enough to do the trick, since Mrs. Potato Head remains Mrs. Potato Head, in her potato body, despite her separation from her eye.) During the transfer, is Mr. Potato Head/Tortilla Face's self in two places at once? Or is there a sudden, instantaneous snap, before which his self is moored in the potato and after which it resides in the tortilla?

    The question reminds me of the essay "Where Am I?" by the philosopher Daniel C. Dennett. Perhaps it has some insights to offer on this perplexing question.


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