Sharing Thoughtspace

A couple posts back, I asked what you thought it’d be like to not have a self. Today, I want to ask a related question with a very different set of implications.

Exactly where are the boundaries of your self?

Maybe you’d say its limits are defined by the physical boundaries of your nervous system. On the other hand, you might define the boundaries of your self more abstractly, and identify them with the limits of your assembled sensory perceptions, feelings, and thoughts.

I choose to imagine that the robot in the thought experiment looks like this.

The tricky thing is, no matter how we try to define those boundaries, philosophers have come up with some mind-bending thought experiments to explore their logical consequences.

Here’s an example. Imagine that in the near future, scientists design a robot that can be remotely controlled by thought alone (this isn’t very farfetched at all, actually). Let’s say the robot is equipped with senses of sight and sound – and by wearing a special virtual reality helmet, you see (in ultra-HD) what the robot’s eye-cameras see, and hear the sounds its audio sensors pick up. Furthermore, wherever your thoughts direct the robot to go, it goes. When you think “turn around,” it instantly obeys.

It’s not hard to imagine that, after an hour or so of wearing the special VR helmet, you’d get the distinct impression that you were somehow in the robot. Your body would still be seated in a chair or reclining on the bed, of course – but where would your self be?

When I say “self,” I’m not talking about the traditional concept of a soul, but something more abstract – the unnamed sense that enables you to distinguish between “a hand” and “my hand;” and to know where you end and another person begins.

In fact, in I Am a Strange Loop, Douglas Hofstadter brings up the idea that in a long-term intimate relationship, it can become difficult to distinguish your preferences and ideas – and sometimes even memories – from the other person’s. In a sense, both of you begin to “think with another person’s brain,” to use Hofstadter’s phrase – or, one might say that both of your selves, to some degree, are represented throughout both brains. It can be blissful or catastrophic, depending on the situation.

This is all a bit abstract, but let’s take a look at a more down-to-earth example. Last week, I was fascinated to read this story of 4-year-old twins with a conjoined brain. Conjoined twins are rare enough as it is, and ones with craniopagus (i.e., who are conjoined at the head) are even rarer – but these particular twins seem to be unique in all of medical history:

Their brain images reveal what looks like an attenuated line stretching between their two brains – a piece of anatomy their neurosurgeon, Douglas Cochrane of British Columbia Children’s Hospital, has called a thalamic bridge, because he believes it links the thalamus of one girl to the thalamus of her sister.

The twins, thinking some deep twin thoughts.

As I’ve mentioned before, the thalamus acts as a relay station for signals entering the brain from the peripheral nervous system – and it also forms a critical part of the thalamo-cortico-thalamic circuits that enable the cerebral cortex to process and respond to sensory data. In short, some doctors think these twins may share – and even actively participate in – each others’ subjective sensory experiences. One might say they’re “experiential roommates” in a way none of us will ever be.

Though the story admits that no controlled clinical trials of the girls’ behavior or neurophysiology have been conducted (their family is understandably wary), anecdotal evidence suggests that the twins exhibit an extraordinary level of nonverbal coordination. Here are some examples:

Krista reached for a cup with a straw in the corner of the crib. “I am drinking really, really, really, really fast,” she announced and started to power-slurp her juice, her face screwed up with the effort.

Tatiana was, as always, sitting beside her but not looking at her, and suddenly her eyes went wide. She put her hand right below her sternum, and then she uttered one small word that suggested a world of possibility: “Whoa!”

“Now I do it,” Tatiana said, reaching for the cup from which her sister was just drinking. She started to chug. Krista’s hand flew to her own stomach. “Whoa!” she said.

“I have two pieces of paper,” Krista announced.

The girls sat at a small table in the living room, drawing, their faces, as always, angled away from each other. Each had one piece of paper. So I was surprised by Krista’s certainty: She had two pieces of paper?

“Yeah,” the girls affirmed in their frequent singsong unison, nodding together.

On the rare occasions when the girls fight, it’s painful to watch: they reach their fingers into each other’s mouths and eyes, scratching, slapping, hands simultaneously flying to their own cheeks to soothe the pain.

Without hard neurological data, it’s hard to speculate in detail about what to make of all this. But one thing seems clear: although the twins have distinct personalities, motivations and preferences, a large amount of their sensory experience is shared – through nonverbal communication and perhaps even direct CNS connections. Reading the story, one gets the sense that the girls’ developing senses-of-self are struggling to define themselves amid a sea of shared perceptions – possibly even shared thoughts. I can’t resist bringing up Hofstadter’s famous “Twinwirld” thought experiment:

[In Twinwirld], instead of people normally giving birth to one person, the normal birth, in fact almost all births, are identical twins. And so the identical twins grow up just basically hanging around together all the time, and they become what I call a ‘pairson’. And they’re two halves; they have the same name, so not even Greta and Freda, but just the same name, but if you want you can append an ‘l’ and an ‘r’, you can call that a left and a right if you want to them.

So here is Karen for example. Karen consists of two pieces, Karen L and Karen R. And here is another ‘pairson’, Greg L and Greg R. And Karen and Greg get married and they have ‘twildren’, Lucas and Natalie. Lucas is a boys and Natalie is a girls. And this is totally normal. This is the way it is in twinworld, and Lucas considers himself to be one thing; he does know that he has two parts, but he doesn’t feel as if he’s divided in two.

This guy's mind is just all over the place.

When I first read about Twinwirld, it seemed like a very strange fantasy. But after reading about the real twins – Krista and Tatiana – it seems that the only really implausible part is the idea that two human minds (i.e., a “pairson”) could ever have completely identical tastes and motivations. But then again, maybe the two halves of a pairson would have debates and fights, just as we all sometimes furiously debate within our own minds – and just as the twin girls occasionally escalate their arguments to physical violence. Bodily limitations aside, it’s not so implausible to conceive of a whole society composed of such pairs.

The fact that a human mind can still develop at all in such an unorthodox environment as the twin girls’ mind(s?) is – I think – a ringing endorsement of the human connectome’s versatility. But most of us are “wired” with a sense of ourselves that assumes a discrete, bounded, and spatially contiguous container for that self: “One Self, One Brain, One Body.” And this message is subtly reaffirmed at every level of human interaction, from the verbal to the societal.

Are these boundaries as sharp as we assume they are, though? In certain situations, such as the relationship example above, another person’s brain can help us think our thoughts – and even form a major part of our self-identity. Some of us may live to see a level of technology that challenges the necessity of a direct correlation between self and body. And as the twins‘ story shows, those ideas may not apply in every case even today.

So, next time you find yourself engrossed in a live video feed of a place in another city, or notice that you’re finishing your best friend’s sentences, you might try asking yourself where, exactly, your self is located. I’ll leave you with a little song for thinking about this.

2 thoughts on “Sharing Thoughtspace

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