Monday, April 01, 2013

A Two-Seater Homunculus

My neighbor Bill seemed like an ordinary fellow until the skiing accident. He hit a tree, his head split open, and out jumped not one but two homunculi. I persuaded them not to flee and sat them down for an interview.

The homunculi reproduce as follows. At night, while a person is sleeping, a female homunculus lays one egg in each of the victim's tear ducts. The eggs hatch and minute worms wiggle into the victim's brain. As the worms grow, they consume the victim's neurons and draw resources from the victim's bloodstream. Although there are some outward changes in the victim's behavior and physiological regulation, these changes are not sufficiently serious to engender suspicion in the victim's friends; the homunculi are careful to support the victim's remaining neural structure, especially by sending out from themselves neural signals similar to what the person would have received had their brain tissue not been consumed. The victim reports no discomfort and suspects nothing amiss.

Each growing homunculus consumes one hemisphere of the brain. Shared neural structures they divide equally between themselves. They communicate by whispering in a language much like English, but twenty times as fast -- much less inter-hemispheric information transfer than in the normal human brain, of course, but as commissurotomy cases show, massive information transfer between the hemispheres is not essential to most normal human behavior. Any apparent deficits are masked by a quick stream of speech between the homunculi, and unlike hemispheric specialization in the human brain, both homunculi receive all inputs and have joint control over all outputs.

Two months later, the person is a two-seater vehicle for brother and sister homunculi. An internal screen of sorts displays the victim's visual input to both of the homunculi; through miniature speakers the homunculi hear the auditory input; tactile input is fed to them by dedicated sensors on their own limbs, etc. They control the victim's limbs and mouth by joint steering mechanisms. Each homunculus is as intelligent as a normal human being, though operating an order of magnitude more quickly due to their more efficient brains (carbon based, like ours, but operating on much different internal principles). When the homunculi disagree about what to do, they quickly negotiate compromises and deferences. When fast reactions are needed, behavior defaults to pre-negotiated compromises and deferences.

But what is it like for Bill? There is no Bill anymore, maybe, though he didn't notice his gradual disappearance. Or maybe there still is Bill, despite the radical change in his neurophysiology? How many streams of experience are there? Two? One for each homunculus but none for Bill? Or one stream only, for the two homunculi, if they are well enough integrated and fast-enough communicating? (How well and quickly integrated would they have to be to share a single stream?) Three streams? One for each homunculus plus one, still, for Bill? Two and a half? One for Bill and one and a half for the two partly-integrated homunculi? Or when counting streams of experience, must we always confine ourselves to whole numbers?

Bill always liked sushi. He never lost that preference, I think. Neither of the homunculi would want to put sushi in their own mouths, though. Bill loved his wife, the Lakers, and finding clever ways to save money on taxes. Bill can still recite Rime of the Ancient Mariner by heart, though neither of the homunculi could do it on their own. When he sees the swing in his backyard, Bill sometimes calls up a fond and vivid memory image of pushing his son on the swing, years ago. When the homunculi consumed his brain, they preserved the information in this memory image between them -- and in many others like it -- and they would draw it up on their visual imagery screen when appropriate. Characteristic remarks would then emerge from Bill, like "Maggie, do you remember how much Ethan loved to ride high on this swing? I can still picture his laughing face!" So spontaneous and natural does it seem to the well-entrenched homunculi to make such remarks, they told me, that they would lose all sense that they are acting. Maybe, indeed, they were no longer acting but really (jointly) became Bill.

I don't know why the homunculi thought I would not be alarmed upon learning all this. Maybe they thought that, as a crazy philosopher who takes literal group consciousness seriously, I'd think of the two-seater homunculus as merely an interesting implementation of good old Bill. But if so, their trust was misplaced. I snatched the homunculi, knocked them unconcious, and shoved them back inside Bill's head. I glued and stapled Bill's skull closed and consulted David Chalmers, my go-to source for bizarre scenarios involving consciousness.

None of what I said was news to Dave. He had been well aware of the homunculus infestation for some time. It had been a closely-held secret, to prevent general panic. But with the help of Christof Koch, a partial cure had just been devised, and news of the infestation was being disseminated where necessary to implement the cure.

The cure works by dissolving homunculi's own skulls and slowly fusing their brains together. Their motor outputs controlling the victim's behavior are slowly replaced by efferent neurons. Simultaneously, the remains of the homuncular bodies are slowly reabsorbed by the victim. At the end of the process, the victim's physiology is very different from what it had been before, but it is a single stream in a single brain, with no homuncular viewing screens or output controls and more or less the victim's original preferences, memories, skills, and behavior patterns.

All of this happened two years ago. Bill never knew the difference and remains happily married, though I had to tell a few white lies about his skiing accident to explain the scars.


Unknown said...

Now that was an interesting story to break up my day!

scitation said...

"Bill" really is John Searle, right right?

Eric Schwitzgebel said...

How did you know?!

Scott Bakker said...

Way cool. Attack of the homuncular phenophages! (

Why does it seem so natural to assume that Bill would have no consciousness of this process of neural conquest and colonization? The fact is, he has no resources to cognize any of the dramatic differences you catalogue in this narrative, and so those differences simply do not exist for him (or for anyone else lacking those resources). On Blind Brain Theory this is what personal identity (and a number of other conundrums) primarily turns on: missing information. Flicker fusion of the soul.

Only the scale makes it seem amazing.

Daryl said...

It's homunculi all the way down.

Eric Schwitzgebel said...

@ Scott: I should have figured you'd have cooked up a similar story! I love your phenophages -- and they're perfect for your brain-blind theory. (I think they'd serve Dennett well too.)

@ Daryl: Indeed! So Bill is and always has been just fine? (What would a Fodorian homuncularist say?)

Liki Fumei said...

I presume Syd Barrett was aware of the homunculi in some extent...

Jorge A. said...

What's the consensus (ha!) amongst philosophers these days? Is our consciousness linked to the matter composing it (hence the homunculi would Kill Bill) or just to the informational pattern?

Peter Hankins over at conscious entities thinks matter is important for the continuity of one's first person experience (I happen to agree, but I flip-flop a lot on this). Bill might not realize he's been hit with the 2-Point Exploding Brain Technique, but he's dead nonetheless. The interesting question is: how many cells do the worms have to eat before Bill ceases to have phenomenal consciousness altogether? Of course, this question has been asked many times before using artificial neurons, but I think the homunculi (or phenophages) are much more interesting because presumably they also have a separate phenomenal consciousness of their own.

Of all the ways to rebuild the ship of Theseus, this one is quite interesting.

clasqm said...

This amazing discovery has ramifications far beyond philosophy.

Politics: Does each homunculus get a vote? Or does each get half a vote?

Law: can Bill bequeath his estate to his homunculi? When Bill takes an oath, is only the homunculus holding his right hand on the Bible bound by that oath?

Gender: Why so casually assume that these are HOMunculi? Could some of them be FEMunculi? You did mention that female homunculi lay eggs on tear ducts- you did not mention how extreme the sexual dimorphism of the species is. Presumably your "brother and sister homunculus" expression is just for convenience and brother-brother and sister-sister pairings also occur. Do the three possible mixes of hom- and femunculi affect one's ahem, orientation?

Finally, you claim to have sat down and tell their story. Tell it to whom? Your two homunculi?

I, for one, welcome our new homunculus overlords. And so do I.

Eric Schwitzgebel said...

Michel: LOL!

Jorge: My guess is that more philosophers would go with informational pattern than with preserving the material, but it's going to be a split vote. (And not all patternists will presumably want to say that the homunculi preserve the pattern; that might depend a lot on the details.) I agree that there's an interesting sorites/slippery-slope issue here.

Callan S. said...

Funny how these never get applied to, say, works of art? A strange sheet like chameleon alien slithers over the Mona Lisa during the night, replicating it's colours and even surface dints and undulation, but consuming the paint and canvas even as it continues to mimic.

So the painting still exists, does it?

I mean, we get into the mechanics of the mind, but then we use examples that are like pulling out the mechanical table cloth from underneath *something*, then showing how really it's all duplicatable by the now naked table since that *something* didn't fall over.

Seems like doing the table cloth trick...without anything actually set upon the table cloth.

clasqm said...

Callan S: An excellent question! As far as the crowds shuffling through the Louvre every day are concerned, the Mona Lisa continues to exist. Functionally, it remains what it was. Things could go on like that for years.

But let's say the French government follows Greece and Cyprus into bankruptcy and decides to sell the thing to China. The switcheroo is discovered. Would the Chinese be prepared to pay a billion Euros for something that is not the actual bits of pigment slathered onto canvas by Da Vinci's hands?

Err, no. At some stage, we humans will drop the functional approach to realty and fall back into substantivism. That's just how we are made.

(A Chinese bio-lab might spare a few million for the opportunity to study this new life-form, but that is a different issue)

This is also the problem with all the loose talk in futurist circles about "uploading your consciousness". As any neophyte programmer knows, there is no such thing as moving data. You COPY data and then wipe out the original. To be able to move data, you'd have to redesign computers all the way back to the Turing machine.

James Patrick Kelly wrote an excellent science fiction novella called "Think like a dinosaur" about 20 years back that explores this.

Callan S. said...

Michel, even synapses - do the 'move' data, or just copy and delete? Spooky stuff.

In terms of conciousness uploading, I've considered perhaps the best you can get is a kind of migration - grafted simulated synapses pressed against the brain, and perhaps over decades the brain 'growing out' into them. With perhaps enough to sustain an intelligence once the biological has gone. A cultivation of inertia, perhaps.