\n<\/p>\n
Kendra Pierre-Louis: For Scientific American\u2019s Science Quickly, I\u2019m Kendra Pierre-Louis, in for Rachel Feltman.<\/p>\n
The French philosopher and scientist Ren\u00e9 Descartes famously wrote, \u201cI think, therefore I am.\u201d What he was getting at, in part, is that though our senses might deceive us, the act of thinking was proof of our own existence.<\/p>\n
But reflect on that sentence again: \u201cI think, therefore I am.\u201d<\/p>\n
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n
Who in that short declaration is I?<\/p>\n
Scientists call that I, that subjective sense of self, consciousness.<\/p>\n
And understanding what consciousness is, how it functions and where it lives in the brain has plagued researchers for generations. I spoke with SciAm\u2019s associate editor Allison Parshall to learn more about the search for consciousness.<\/p>\n
We explore what consciousness is, how the brain creates it and what current science says about dreams, anesthesia, animals and even artificial intelligence.<\/p>\n
So you recently reported a feature in the February issue of Scientific American on consciousness. What kind of sparked your interest in the subject?<\/p>\n
Allison Parshall: Well, I studied cognitive science in college, and consciousness is kind of the big question that looms over a lot of neuroscience, whether it\u2019s, like, being addressed head-on or not.<\/p>\n
There were these really famous split-brain studies many decades ago [with] people who were having seizures and they would try to address it by cutting, basically, the connections between the two brain hemispheres. And this would result in some really weird things where, like, there was information in your brain that you had but you weren\u2019t conscious of because consciousness was, like, in one side of the brain and not able to access the other.<\/p>\n
It\u2019s inherently very interesting, right? It\u2019s, like, the big question of, \u201cHow do I have a perspective? How is it that my brain is yielding me having a feeling of being me?\u201d It\u2019s, like, a very philosophical question, so as someone who is interested in cognitive science as a very interdisciplinary field the philosophy of it all was very interesting.<\/p>\n
Pierre-Louis: One of the things that I thought was really interesting in your piece is: scientists don\u2019t have a set definition of what consciousness is. But can you describe at kind of a high level what they\u2019re trying to explore when they\u2019re studying consciousness?<\/p>\n
Parshall: The English word \u201cconsciousness\u201d is a little bit of a mess, so we have to kind of forgive it for that, but it\u2019s referring to a lot of things. I mean, first off, you can just think of it as whether you are conscious or not\u2014like, are you awake or not? Are you\u2014have you been knocked unconscious? Are you, like, blinking? Are you aware?<\/p>\n
And then there\u2019s also kind of what you are experiencing while you\u2019re aware, so there\u2019s this sense of subjective first-person perspective that is really kind of the source of a lot of the mystery here. It\u2019s like, \u201cWhy is it that, as I\u2019m sitting here, I am seeing through my eyes and having a holistic, unified experience of me as a person, and that is connected to every other state I\u2019ve ever been in, and it\u2019s all kind of this unified stream?\u201d<\/p>\n
It\u2019s not clear how that comes out of the brain because the brain is this, like, physical piece of matter\u2014it\u2019s a very complicated one. So there\u2019s this age-old question in the philosophy of mind and philosophy of science and everything, [which] was, like: \u201cHow are the mind and the brain connected? Are these fundamentally the same things, or are they two separate?\u201d It\u2019s, like, this war between this idea of dualism, where, like, the mind is something kind of separate from the brain and there\u2019s, like, a gap between what you can explain by just looking at the physical object, and this idea of materialism, which is, like, everything we are, everything we perceive all comes back to the physical matter of our brains.<\/p>\n
Science tends to kind of go with materialism, just because it\u2019s almost an assumption you need to make in order to get anything done. But it\u2019s been very challenging for neuroscientists to really close that gap, to understand what it is about our first-person experience, where it is coming from in the brain, how is it that the brain is kind of all coming together to make this happen for us\u2014it\u2019s very hard to explain, and nothing\u2019s really been proven [Laughs], is effectively what\u2019s happened.<\/p>\n
Pierre-Louis: One of the things that I thought was interesting, as someone who\u2019s, like, been under anesthesia, is that when we\u2019re under anesthesia or under hallucinogens we lose consciousness. But when we dream, which many of us kind of think of as, like, an altered state, we\u2019re still tethered to consciousness. Can you talk a little bit about that?<\/p>\n
Parshall: That is such a good question. I think about this a lot. I had to get my appendix out while I was reporting this story, and I was trying to get them to do this test on me to see if I, like, maintained consciousness \u2019cause sometimes people can maintain some connectedness, and they didn\u2019t know what I was talking about. I was a little disappointed. [Laughs.]<\/p>\n
Pierre-Louis: [Laughs.]<\/p>\n
Parshall: Some scientists are proposed kind of a multipronged dimension\u2014like, way of thinking of consciousness. There\u2019s kind of three dimensions that I think of when we think about consciousness. One of them\u2019s wakefulness: Are your eyes open, frankly? Like, are you blinking? Are you conscious in that way? Another one is internal awareness, so do you have a sense of yourself\u2014not necessarily your environment but, like, of your own internal states? Do you have a monologue kind of going? And then, three, connectedness, and that\u2019s where it\u2019s, like: Are you connected to your environment? Are you sending and receiving signals from your brain to your body about what your body\u2019s experiencing and how your body is interacting with the world?<\/p>\n
So in dreaming you don\u2019t have wakefulness, and you don\u2019t have connectedness, but you do have internal awareness. So that\u2019s kind of, like, a special altered state of consciousness. Under anesthesia you really don\u2019t have any of those, ideally, but sometimes people maintain connectedness, and that\u2019s a problem; we don\u2019t want that to happen. But yeah, it is fundamentally pretty different. Obviously\u2014like, there\u2019s some question of, like, \u201cDo you lose consciousness fully when you go under anesthesia?\u201d but that\u2019s a little bit outside my wheelhouse.<\/p>\n
Pierre-Louis: So we\u2019re talking a lot about how difficult it is to define consciousness, and one of the things that stood out to me was that beautiful quote by Marcello Massimini, neurophysiologist at the University of Milan, who\u2014I\u2019m gonna, like, read off the quote verbatim \u2019cause I just thought it was so beautiful, when he\u2019s talking about the brain …<\/p>\n
Parshall: So did I.<\/p>\n
Pierre-Louis: As \u201can object with boundaries, with a given weight, a little bit like tofu. It\u2019s not particularly elegant,\u201d but \u201cinside this object that you can hold in your hand, there is a universe,\u201d and I just feel like that really gets at the difficulty of what we\u2019re trying to wrap our heads around.<\/p>\n
Parshall: Yeah, part of the reason I love that quote is he was talking about his first experience in medical school holding a brain. I never went to medical school, but I did hold a brain in college, and it profoundly shook me because it\u2019s, like, this was someone\u2014I think it was a woman\u2014like, this is a person, and I\u2019m holding them, and, like, it\u2019s kind of no longer a person anymore.<\/p>\n
There\u2019s this interesting thought experiment from the philosopher Gottfried Leibniz, who thinks about the mind as, like, an analogy of, like, a mill\u2014like, a mill that grinds …<\/p>\n
Pierre-Louis: Like a grain mill.<\/p>\n
Parshall: A grain mill, yes. And the question of, like, if you could walk inside your brain like you can walk inside a mill and see all of these, like, not levers but, you know, mechanistic things happening, the question is, like, \u201cWhere would you see thought? Like, where would thought emerge?\u201d But that\u2019s, like\u2014it\u2019s kind of circular, right, \u2019cause then you are a being inside the mill, and you have subjective experience\u2014it\u2019s a little bit of a mess.<\/p>\n
I think that\u2019s why is\u2014this topic is so compelling to people and so compelling to me is this: How do you bridge this gap? There\u2019s some scientists that think you can\u2019t. And so that\u2019s kind of where a lot of the story comes from here, is: Can we bridge this gap? Are the tools of science even capable of letting us understand what\u2019s going on when we are fundamentally trying to understand our own experience?<\/p>\n
So that\u2019s where the tagline of the article, like, \u201cThe Hardest Problem,\u201d comes in. There\u2019s this idea of consciousness as a hard problem. There\u2019s, like, the easy problem, which is: \u201cCan you look at the brain and figure out which areas are related to consciousness?\u201d But then there\u2019s the bigger question of, like, \u201cHow does this subjective quality emerge?\u201d Philosophers sometimes call that \u201cthe hard problem,\u201d and I think there\u2019s a case to be made that this is one of the hardest problems for science to solve because we are fundamentally subjective beings looking outward from our inward selves that are locked in and we\u2019re trying, in this case, to access something that is fundamentally locked in. It\u2019s very challenging to measure.<\/p>\n
Pierre-Louis: It sounds like it.<\/p>\n
I know that you walk us, in the piece, through several theories of sort of where consciousness may lie, and most of those theories kind of are looking at different aspects of the brain. But one theory that I wanted to highlight was the integrated information theory [IIT] …<\/p>\n
Parshall: Yes.<\/p>\n
Pierre-Louis: Which is a mathematical and a philosophical theory that kind of stands out. Can you talk about that theory?<\/p>\n
Parshall: Yeah, like, you said it right: like, a lot of the theories of consciousness kind of look at the brain and look at what areas light up when you\u2019re consciously aware of something versus when you aren\u2019t and basically squeeze the juice, as some people say, squeeze the juice of consciousness from the brain.<\/p>\n
This theory is very interesting \u2019cause it takes kind of the opposite approach. It starts with our subjective philosophical observations of what consciousness feels like …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: And kind of tries to boil it down to a couple principles. So there\u2019s five principles; I won\u2019t go through all of them. But what they kind of come down to, in the end, is this idea that your consciousness is unitary, so you are only ever experiencing one stream of consciousness …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: At any point. Even though, like, you could feel maybe you have a toothache and also you\u2019re worried about your mother, and, and these are two separate things that you can distinguish, you are experiencing them as one whole. So that\u2019s the kind of the intuition they\u2019re pulling there. And also this idea that it\u2019s very information-rich. So, like, even if you close your eyes, just from, like, an information theory perspective, there is a lot differentiating one state from another. Like, if I\u2019m watching a movie and I\u2019m perceiving one scene versus the next scene, like, that is even very different. And these two ideas of, like, everything being integrated and everything being very information-rich …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: Is kind of like where the theory gets its name, because when you combine these two, you can say, \u201cOkay, this is all about information that is integrated.\u201d<\/p>\n
Now, I feel like I\u2019m already starting to lose the plot a little bit …<\/p>\n
Pierre-Louis: [Laughs.]<\/p>\n
Parshall: Because we\u2019re getting so abstract, but what this practically means is that you apply this to the brain\u2014which is not, like, an, a non-substantial leap; like, to be clear, like, there\u2019s some extrapolation going on here\u2014we have all these brain networks …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: And these brain networks talk to each other, and they contain a lot of information within them, and then they pass a lot of information between them. And one of the things that happens when you lose consciousness in anesthesia and in other\u2014like, when you, you know, fall into a dreamless sleep is that these networks kind of stop talking to each other. Basically, your brain is kind of running on information that is integrated. When you lose consciousness, it is less integrated. Therefore, that\u2019s part of, like, why you lose consciousness.<\/p>\n
And it\u2019s, like, a little wonky, but we have developed some pretty interesting measures to study this, so there\u2019s a way you can use a magnetic coil to kind of zap parts of the brain and see what happens. In [a] fully awake brain there will be kind of, like, ripples upon ripples upon ripples spreading out because everything is so information-rich and integrated. In an unconscious brain or a brain that is maybe in, like, a minimally conscious state following a brain injury, you see a lot less of those ripples.<\/p>\n
So they have tested this and, like, developed these measures to kind of be able to see what level of consciousness someone is at. But that can\u2019t really explain, like, if you are fully conscious, what\u2019s the difference between experiencing a toothache and experiencing the siren outside that\u2019s so loud it\u2019s blaring your ears out. Like, that difference in what they call qualia, or, like, the qualitative state …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: Is very hard to assess.<\/p>\n
Pierre-Louis: Does this also suggest, \u2019cause I feel like we\u2019re in a moment with all of this, like AI talk where people\u2014and, you know, we\u2019ve grown up on …<\/p>\n
Parshall: Mm-hmm.<\/p>\n
Pierre-Louis: Movies like The Terminator\u2014where people really wanna believe that machines can be conscious, and so does this model, because it\u2019s not pulling directly from the brain, suggest that, in theory, we could create a network that is conscious?<\/p>\n
Parshall: Yes and no. [Laughs.]<\/p>\n
Pierre-Louis: [Laughs.]<\/p>\n
Parshall: I think, like, there\u2019s some ways in which that theory, because it doesn\u2019t assume consciousness needs a brain, right …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: Like, it\u2014that\u2019s one of the reasons it\u2019s criticized sometimes, and I don\u2019t know if this is a very fair criticism, but the idea that, like, \u201cOh, if consciousness is just about information, you could imagine a computer chip that\u2019s conscious,\u201d it\u2019s like, \u201cWell, yeah, okay, sure, we could take it to that extreme.\u201d<\/p>\n
The prominent thinkers who support IIT at this moment don\u2019t think that our current large language models could do this, partly just because of their structure. Basically, like, what it comes down to is: these computer chips aren\u2019t actually integrated in a way; they\u2019re simulating neural nodes that are integrated. And it\u2019s kind of a little bit of a challenging hair to split. The supporters of this theory don\u2019t necessarily think that, like, ChatGPT\u2019s, you know, anywhere close to becoming conscious.<\/p>\n
But this question of AI is, I think, really what drove a lot of my interest in understanding where the field of consciousness research is now because it\u2019s kind of lighting a fire under everybody, right? Like, when Google\u2019s LaMDA model, the machine was saying it\u2019s sentient …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: A lot of people were kind of turning to these consciousness researchers to be like, \u201cOkay, so what have we learned about consciousness? Can you extrapolate it from the brain into these machines?\u201d And most AI people don\u2019t think that AI is anywhere close to consciousness, but I think it, it really highlights some of the limitations of neuroscientists\u2019 understanding of consciousness that you kind of can\u2019t take it out of the brain. And even the theories that don\u2019t involve the brain have a really hard time figuring out, like, what ground truth elements of this are we gonna port over from our brain theory into the AI theory?<\/p>\n
Pierre-Louis: I guess my last kind of very pressing question: Is my sister\u2019s cat conscious? [Laughs.]<\/p>\n
Parshall: [Laughs.] Well, so the non-human animal question of consciousness is really also one that\u2019s taken off a lot in the past, like, five to 10 years. We have come a long way from where we used to be in kind of, like, the \u201990s, according to the sources that I talked to, where we really could only assume that the only animals that had consciousness were humans because it\u2019s, like, we can\u2019t ask the cat, right? But we can do experiments carefully designed so that the most, like, parsimonious explanation is that this animal is conscious. And we\u2019ve done those, and we\u2019ve done them\u2014also neurobiological studies. And I think, at this point, like, there\u2019s fairly wide consensus that all mammals are [probably] conscious.<\/p>\n
Just because they\u2019re conscious beings navigating the world doesn\u2019t mean that they have, like, the cognitive capacity to threaten us or anything. And that\u2019s the exact same case with AI: just because they\u2019re able to do things that humans can\u2019t do and are deemed pretty intelligent, if you wanna grant that to them, doesn\u2019t mean that there is a first-person subjective conscious experience.<\/p>\n
And then there\u2019s another important distinction to make, which is that, like I said, the English word for consciousness is really messy …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: And it kind of encompasses both this sense of, like, being an agent in the world, like, sentience\u2014like, a rock is not sentient, but an, an nematode probably is\u2014with self-awareness, like, this awareness of yourself and this ability to think back on yourself and reflect. When animal-consciousness researchers talk about consciousness they pretty much just mean sentience.<\/p>\n
And so there\u2019s a question of, like, okay, now at this point a lot of the researchers I talked to said that the frontier kind of lies with fish and insects …<\/p>\n
Pierre-Louis: Mm-hmm.<\/p>\n
Parshall: So, like, that\u2019s where the main area of question is. Like, we\u2019ve ran mammals, pretty much. Fish and insects, we have some very interesting kind of preliminary research that, like, fish can recognize themselves in mirrors. It\u2019s not clear where the line gets drawn.<\/p>\n
So all that to say your cat\u2019s probably conscious, in my opinion [Laughs] …<\/p>\n
Pierre-Louis: [Laughs.]<\/p>\n
Parshall: But what, what it will take for science to kind of prove it I think very much illustrates some of the limitations of proving consciousness in any case.<\/p>\n
Pierre-Louis: Where can we find your work?<\/p>\n
Parshall: You can find the feature article that this conversation was mostly based off of at ScientificAmerican.com. It\u2019s in the February 2026 issue of the magazine.<\/p>\n
Pierre-Louis: Thank you so much for your time today.<\/p>\n
Parshall: Of course. Thank you.<\/p>\n
Pierre-Louis: That\u2019s all for today. Join us on Friday, when we\u2019ll explore the mystery of long-lost DNA.<\/p>\n
Science Quickly is produced by me, Kendra Pierre-Louis, along with Fonda Mwangi, Sushmita Pathak and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.<\/p>\n
For Scientific American, this is Kendra Pierre-Louis. See you next time!<\/p>\n","protected":false},"excerpt":{"rendered":"
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