Hey Vsauce, Michael here,
and a hemispherectomy is a surgical procedure
in which half of a person's brain is removed. It's usually only ever done
on very, very young patients because their brains are still plastic enough that the remaining half
will take on the functions of the half that was removed. And it's usually done
because a young child or a baby is having seizures, and removing
the part where the seizures occur is the only solution. But here's my question. If you can live with half a brain, what if I were to take two empty skulls and take one half of your brain and plop it into one body
and the other half and put it in another body, which person would be you? I mean, you are you.
You are conscious. You are aware of what is happening to you from the perspective of yourself.
Think of it this way. If you just stare at something
and kind of feel what it feels like to be you, it feels a little bit like you're a thing inside a body looking out through the eyeballs. And nobody else on Earth will ever see the world from that position. This awareness of your own experiences, the awareness that you are having them, the awareness that you
are having your own thoughts makes up what we call consciousness. But if I were to take your brain
and split it into two and put it into two different people, would both of them be new people
who were conscious? Well, one of the best places to start when defining consciousness
and understanding it is to begin with things that we agree
are not conscious. For instance, Cleverbot. Cleverbot.com is an amazing website where a computer program will respond
to your questions really cleverly but only because it is programmed to do so. We wouldn't consider it conscious because it doesn't have a sense of itself. It doesn't feel anything.
It doesn't have its own inner life. It's just a program that responds
automatically to my inputs. Now I know that I am not like Cleverbot. I know that I feel things
and that I have a sense of myself. I have intentions. But how do I know that you do? For that matter, how do I know
that everybody else that I meet is like me? How do I know that they're not
just little smart versions of Cleverbot who know exactly what to automatically say? Now what I'm asking is incredibly philosophical, but it is a very famous and important question. I'm basically asking if it's possible
for something to exist as a philosophical zombie. That's right, a thing that reacts and responds
and acts just like a normal human but yet doesn't actually feel anything. It doesn't know that it's having its own thoughts. It just automatically responds like a robot
in the appropriate way. Now what's amazing and heavy about this question is that science doesn't have an answer, and it's not even clear that science
will ever have an answer, let alone an approach to finding that answer. About all we have is the psychology
of disorders of consciousness. Let's begin with anosognosia. A common example of anosognosia
in psychology classes is a patient who has, say, lost the ability
to move their left hand. When asked to raise their right hand, they'll say, "Yeah, no problem, here you go." But then when asked to raise their left hand, they'll say, "Oh, yeah, sure, no problem," but not move it.
And when asked why they didn't move their left hand, instead of reporting that they can't, they'll confabulate some excuse. For instance, "Oh, I didn't feel like it." Anton-Babinski Syndrome
is even more dramatic. Patients with this syndrome
are cortically blind. They cannot see anything. But they deny being blind. If you ask them a question, for instance,
"How many fingers am I holding up?" they will make a guess,
but if they're wrong, they'll explain their inaccuracy
with an excuse. For instance, "oh, well, I don't have my glasses." People who exhibit anosognosia tend to be the victims of stroke, and there's some disconnect
between what they're really experiencing and their conscious awareness of it. They don't know that they can't see because the part of their brain
that monitors visual input isn't telling the brain anything. It's not even telling the brain
that there is no visual input which means that the parts of their brain responsible for answering questions
or creating speech has to completely create
a confabulated response. Despite the fact that we've been able to study patients with anosognosia,
we still have no idea how to solve our original problem. In fact, all we've managed
to come up with are more impossible questions
about identity, questions that are so befuddling,
the best you can do with them is to answer them yourself
according to what you believe. Here's another one.
It's called the Swampman. Imagine that I'm walking
around in a swamp and then all of a sudden,
I get struck by a bolt if lightening and my entire body is burned to a crisp,
dissolved into smithereens. But the very same moment,
a second bolt of lightening strikes nearby, and it causes a bunch of atoms and molecules to all arrange themselves
into the exact same configuration that my body used to have,
making a second Michael. Is that me? Would that be me? Here's an even better one.
Imagine that a surgeon came in, and he started removing cells
from me and from you, replacing them exactly one at a time, replacing my cells into your body
and your cells into my body. At what point would I
officially have become you? No one on Earth has the definitive answers
to these questions, but you know what we do have?
A lean back. That's right. I've made a playlist
of some of my favorite clips from all over YouTube of psychology experiments and illusions and all sorts of fun stuff
that deal with consciousness. All you have to do is click the link
at the top of this video's description and then lean back and let the automatic playlist
do the work for you. I'll see you over there, and as always,
thanks for watching. Hey Kevin, any new YouTube messages? Actually yes. I just got this message
over at Vsauce 2 from a user who doesn't create videos but he organizes them in his own playlists. Yeah, yeah, that's excellent
because there's so many videos on YouTube, we need people to help organize them,
especially by type. Imagine a channel of playlists ranging
from cool songs to listen to when it rains or best explosions ever. Exactly. If you make a playlist
that you think is really cool and full of stuff that we should know about,
send it to Michael@Vsauce.com and we'll feature the ones we really like because you have made YouTube
a better more organized place. And after all, Vsauce is kind of like a carpool lane. We're all going to get
to the cool stuff faster because we're traveling together. Where did you get that?
These are strange things to think about for sure. I'm in my fifth year of university psychology now and I'm still blown away by the complexity of that little grey mass in our heads. Another interesting thing to consider is that we are not the same material bodies as we were several years ago. Each day we loose thousands of epidermal cells from fallen or rubbed-off skin, blood from wounds and fecal matter and biological substrates from our urine. We loose cells in our saliva, out our sneezes and coughs, by shedding our hair and clipping our nails. So when he talks about at what point do "I" become "you" if we were to exchange cells one by one - the more interesting question (at least for me) is when do "I" (present) become replaced by the "me" of the future?
Favorite channel on youtube and favorite episode on channel
I've been thinking about this for a while.
I think we are never the same person. We are never A person. We are only sensory input and the memory of that sensory input. What we call consciousness doesn't exist, it is only the combined effect of the sensory input and the memory of it.
If a brain would be split in half and put in two different bodies, you would have what we would call "two people", they would not be the same person. Though my theory is that there are no "people", only inputs and memory.
What song is playing in the background? It's really catchy.
Leanback. There goes my morning.
Vsauce is freaking awesome.
why does there have to be background music?
I've always wondered about how consciousness works at a quantum level. Given that the current thinking is neurons transmit electrical charge and the change in potential charge, in parallel with other neurons, represents our consciousness. Does that mean our minds subconsciously control electrons to create our consciousness?
This is less of a philosophical problem rather than a communication problem. What is the definition of "me"? There is no set limit on what you can define as yourself and thus you don't know what parts are replaceable as such.