Transcript for Michael Gazzaniga uncut

 

Steve Paulson: Speaking with Michael Gazzaniga, whose new book is called "Who's in Charge: Free Will and the science of the Brain". Twenty or thirty years ago, it seemed that there was a great vogue and people talking about the left brain and the right brain, and that those distinctions were often dismissed by lots of brain scientists. And then, more recently, it seems there is renewed interest in the differences between the two hemispheres of the brain. Can you briefly outline this history, and sort of tell us how scientists have come to where they are now?

Michael Gazzaniga: Well, it's a moving target. It started through a large extent over research that I was part of back in 1960. What we were doing was studying patients who'd had their hemispheres separated in order to control their epilepsy, and we could study the special functions of each side without the other interfering. And so, one of the things we made obvious note of, is that the left hemisphere is the language and speech side of the brain, and the right hemisphere is specialized for other things that involved perceptual, motor, sort of coordination. And so, that quickly, that quickly became left brain right brain analytical versus synthetic, intuitive and so forth. It was picked up, sort of, by lots of people, including the advertising industry, and it got sort of out of hand. Then, it was put in perspective, but people still, now I think it's just become a term that people use to reflect the different cogent of styles of people we know.

Paulson: Right, the short-hand is that the left brain is the analytical side of the brain, the right brain is intuitive. Is that basically accurate, or not?

Gazzaniga: No, it's basically half-accurate. The left brain is the analytical, language-based system, but intuition comes about through processes that are A, unknown, and B, probably involve many similar neural structures that are involved in language and higher-order thinking on the left side, so it's overstated.

Paulson: So, it sounds like scientists are refining some of those early ideas, I mean, there's a much more complete idea of how these two hemispheres work together, more complete than even, say, twenty years ago.

Gazzaniga: Oh yeah, and it's changing all the time because, now, with brain imaging technology, one can study which parts of the brain are active in a whole variety of cognitive and social, even, activities, and one finds different parts of the right brain involved in all kinds of activities that heretofore had not been thought of. A lot of social processes, a lot of... For instance, the rules that we use and judging whether something is fair seems to be heavily involve the right frontal lobe processes and so forth. So, the story's become much more complex as these things always do, and the, on the other hand, we're much more informed about how it all works too.

Paulson: You are one of the scientists who created the field of cognitive neuroscience, and I know your early studies of people with the split brains really launched you into this field, and... First of all, can you take us back to these? Why did some people have these split brains?

Gazzaniga: Well, again, they were patients who suffered from epilepsy, and it was the kind of epilepsy that was not cured by drugs, by the pharmacological agents that were available. And so, the idea goes back to an old idea that if you maybe isolated where the seizure started, if you had a way of isolating it to a part of the brain, the other part of the brain wouldn't go into a seizure. And then it could maintain sort of conscious awareness during a seizure. So, very simply, if a seizure, say, started at a faux site, is the word they used, had started in the left hemisphere, maybe by splitting the brain it wouldn't spread to the right. And then, when the seizure did occur, only half the body would be affected and the other half would remain seizure-free. And, kind of what happens, they said, let's do these surgical procedures, and see if we can help some people. What can happen was that overall their seizures were just reduced, it wasn't that they became as frequent and were localized, it was just the overall level of seizure activity became actually dramatically reduced, and then the surgeries took hold, and was done on a number of cases throughout the world and the United States in particular, but that's now sort of given a way to the fact that the drugs for controlling seizures are better and the surgery isn't done that frequently any more.

Paulson: The thing that was remarkable about some of those early patients who had the surgery was, it seemed they could go ahead and have their brain severed in half, and they wouldn't have any side effects. And then you came along, and tested that hypothesis.

Gazzaniga: Yeah, so there had been a series of patients done in the 1940's at the University of Rochester, a very famous series of patients, and it seemed there were no effects at all, and in some sense, there are no effects in the sense that, if someone had a split brain, you wouldn't know it. It only becomes evident about these information transfer problems, if you'd test them in a special way. In everyday life, everything seems utterly natural and integrated. So, anyway, we did the experimental testing that showed the fact that there was a dramatic change in the sense that one side didn't know what the other was doing and then we could study these specialized functions. So that was a big breakthrough that came in the early 60's.

Paulson: Can you tell me about one of those early studies, how you actually figured this out?

Gazzaniga: Yeah, I remember it like it was yesterday. We tested this one patient known in the literature as "WJ" and what would happen is that I first tested him preoperatively, so I would flash pictures to him... Either side of fixation point, so... Just for your listeners, if you fixate a point in space, everything to the left of the point is projected to your right brain, everything to the right of the point is projected to your left brain. That's how we're all wired up. So if I showed you an apple in one part, to one side of fixation, an orange to the other, you'd name both of them because the information's integrated because this great commissure that connects the two brains is intact in you and me. Once you split the brain, for the surgery, what happens is you can only name the one presented to the right visual field because that goes to your left, speaking hemisphere. So that's what we know now but at the... Rolling the camera back to 1960, the patient had his surgery and came back to CalTech where these studies were done with my mentor, Roger Sperry, and we put the patient in front of the screen and flashed a picture, and he named the one to the right because that goes to the left hemisphere, he said apple, and when the other one came up he didn't say anything. Nothing happened. So, anyway, to make a long story short, we then let switch from the speaking mode to letting his hand point to where the stimulus came up and sure, he'd do that and then, through a series of tests involved over years we found out that the right hemisphere understood quite a lot and could point to answers, but just couldn't speak about them. So that gave rise to the basic syndrome that was then studied and has been studied, continuing to be studied fifty years later.

Paulson: And you also did a study that did, sort of this remarkable conclusion, that involved a chicken claw and a shovel. Can you describe that study?

Gazzaniga: Yeah, that study came twenty-five years later. So, the idea was, we were going to present each hemisphere with a simple task. They had to match a picture flashed with a set of options in front of them, and we wanted to see, can each hemisphere respond simultaneously, and then ask them about it. So what we did was we showed a chicken claw to the right visual field, that means it went to the left hemisphere, and there were four pictures in front of the right hand, one of which was a chicken. Chicken claw would go with the chicken. And then to the left of fixation point, we showed a snow scene, a nice New England snow scene, and then there were four choices for the left hand, one of which was a shovel. So we flashed the pictures and instead of asking the patient what they see, it took us twenty-five years to figure out why don't you just say it, let them point to objects and then ask them why they did that. And so, that's what happened, and the patient repeatedly pointed to the chicken and to the shovel as the most related, which were the correct answers, but then we asked, so why'd you do that? And the patient quickly just snapped and says, and this is the left hemisphere talking, the patient says, oh, the chicken claw goes with the chicken, and then you need a shovel to clean out the chicken shed, I emphasize that, shed. And there was this left hemisphere process which, a special system it has which we've dubbed, called the interpreter. Making a story up to fit the actions that we're pouring out from all these systems, in this case it was this very controlled experiment, but it became the storyline for the fact that we're full of these separate, unconscious modules that are producing behaviors in us and once they're out on the table, we then think about them or are asked about them and reflect on them, we cook up a theory as to why we did what we did.

Paulson: So this person had this image of a shovel, but hadn't actually seen the snow with the left hemisphere, and so came up with an entirely different explanation: oh, you need the shovel to clean the chicken shed.

Gazzaniga: That's right, that's right.

Paulson: So you, the take-away here is that the left hemisphere, what you called the interpreter, makes up all kinds of stories, basically creates a narrative that often isn't really there?

Gazzaniga: Well, I think, yes, that's the idea. Except I think it usually is the narrative. This is you and me talking now. I mean, we have these things, the same applies to us. And so, we are constantly trying to figure out why we behave in a particular way, why we have a thought of a particular kind, why our emotions are particular, in a particular mood state, and we apply a narrative to that state, and this goes on constantly in us all day long, and this is an explanation for how that narrative, how that, as some people call it, a story-telling mind of ours, keeps us living under the illusion that we're this wonderful unified person with a single self that's in control of all of us.

Paulson: This raises a huge philosophical question, I mean, this is something that philosophers have debated about for centuries, but it seems that it's now basically in the realm of science, which is, how do we come up with this sense of the unified self, because, there's no particular part of the brain that actually creates this unified self, is there?

Gazzaniga: Well, there's a lot of work done on that, and there's dimensions through self and other relationships that apparently use all kinds of different regions of the brain, modern studies hold up, but there is this one system in the left hemisphere, this interpreter, this module if you will, this processor, which ties all the events and changes in behavior that are produces by these separate modules into a narrative, into a storyline. And that, I think, gives rise to the illusion of a unified self, yes.

Paulson: And there's another question, perhaps even a deeper philosophical question, which is: what is consciousness? And I know there are a lot of scientists and philosophers who say we will never understand consciousness, the age-old mind-brain problem, I mean, to put it bluntly, how do the physical mechanics of the brain, the neurons, the neurotransmitters, the synaptic connections, how do they somehow create mental experience? Have you come up with any answer here?

Gazzaniga: I can tell you that it's not unpaged or whatever. That is the sixty-four dollar question and to have the view that it'll never be understood, I think, is a strong claim because, if you just look back sixty years, we had a pretty measly understanding of what a gene is, and in fact, in the last sixty years we produced this phenomenal body of molecular, biological and genetics that is responsible for all our modern medicine and actually, we still don't know what a gene is because it has become so much more complicated to think about. So, we have this situation where just because we can't fully define something, people think, well, it'll never be defined and we shouldn't work on it till we get it defined. I don't agree with that, I think that we have plenty of examples in science where something's not really nailed down in full definition, but yet advances are made on it and understanding is gained, and that the same is going to be true for the problem of consciousness.

Paulson: What is your working definition of consciousness?

Gazzaniga: Well, I have, I mean, the system that allows for phenomenal awareness on a moment-to-moment basis. Whatever that thing is. Now, what is that? Saying it is easy. It's thinking, at what level do you want to understand it? Whether there's going to be a neurophysiological level, whether it's going to be an interaction of the neural level and the mental level, using some new vocabulary that we don't quite yet understand, I kind of think that's where it's going to go, and I think that is the challenge of modern neuroscience, figure out how these layers interact, because I think there are layers and they interact and the secret to the mind-brain/consciousness problem comes from that. I don't think consciousness is a single process for which something is passed through and it becomes conscious, that you become conscious of it. I think whatever is enabling the phenomenon of conscious experience is widely distributed in the brain and associated with each domain, with each cognitive, perceptual thing  that you're currently conscious of. It's associated with that specific problem and enables it to your consciousness. So it's a parallel distributed system, the cellular, physiological basis of which I have no idea, and no one else does either.

Paulson: Okay, well, let me ask the question in perhaps a more pointed way, will we ever able to figure out why a particular thought pops into our head by looking at the physical mechanics of the brain, you know, the neurons, the transmitters, all of that.

Gazzaniga: Well, it will be a difficult assignment. The question is the level of analysis that will be applicable to that question. As a colleague put it to me, if you had a computer large enough to store all the biophysical events and processes ongoing in the brain, and you wanted, so you had all the information possible on it, and you put a cookie and a glass of milk in front of a hungry football player, and you wanted to use that information to predict what will happen, the computer isn't big enough, and you don't have enough time in life to have it compute the answer, whereas if you just use folk psychology, you probably get a hundred percent right, instantly. So, this notion that we're going to understand everything by applying all these modern techniques and knowledge and quantifications to a simple question like that is, I think, not the way to think about it.

Paulson: But yet, it would seem that, until you can answer that question, you know, what causes a particular thought, I mean, why do we have that particular thought, until you can answer that, you're not solving the consciousness problem.

Gazzaniga: Well, you know, this gets back to the question that, solving the consciousness problem is an easy thing to say we want to claim to be able to do, but if the answer were available now to you in a book, you wouldn't recognize it, because we haven't brought ourselves along far enough to know what the question is yet. We're studying all the time phenomena that grab our attention because them seem related to consciousness. A patient has a funny behavior because of a lesion here, there's brain activity before this event over there, and you, by piecing all this information together you're kind of getting closer to knowing more about consciousness, without still having defined the problem accurately or without knowing all the details on how our particular decision is made. I think you have to live with that, just sort of reality, that's how it goes.

Paulson: And your larger point, in terms of how the brain works, especially the human brain, is that there's not one overarching system here, there are actually millions of little modules within the brain, each making its own decision and somehow, they come together and create this sense of consciousness that we have.

Gazzaniga: That's right. That is, there's activities going on on different timescales and there's, using the word emergent on a simple level, where the processes going on on one level create the next level, our next layer, without that layer being able, without the lower layer being able to predict exactly how the upper layer works, and all of that is going on in this massive piece of tissue, through all these layers, how does that work? That is just a massive, massive problem, but we're working on it, as they say.

Paulson: You've talked about the mind as an emergent phenomenon in some way, that somehow there are these different layers of organization and one feeds into the other. Can you spell that out a little bit? What would these different layers be?

Gazzaniga: You know, let's take the physical model that, we thought we had our laws of physics with Newton and determined it was the answer and we understood how billiard balls worked precisely and we can put rockets on the moon, and everything's working fine, and then, you know, in the 30's, late 20's - 30's along came quantum physics that says, yeah, but those Newtonian laws don't seem to explain the behaviour of these molecules, so you had the Heisenberg uncertainty principle. Therefore, there's wiggle room and yet, all that indeterminacy that was discovered in quantum mechanics can produce something that is very determined, that works on very deterministic rules, which is to say that all those molecules bumping around with indeterminacy produce billiard balls and those follow very strict Newtonian laws. So, in some sense, that's an emergent property that the underlying quantum-mechanical atoms produce this thing that's there and follows these strict laws. You could say that's an emergent thing.

Paulson: Okay, so how does that apply to the brain then?

Gazzaniga: Neurons interact in a way to produce a mental state that we all enjoy. That mental state can, and in fact, interacts with the layers that produce it and constrain the layer that produces it, namely the neurons themselves. An example that's related can be explained like this: if you take depressed people and give them a clinical trial of just talk therapy, there's an improvement to a certain degree, and if you take another group and you give them pharmacological aids, they improve to a certain degree, and then you put them both together, with all the proper controls and so forth, there's a far, far greater extent, there's some sort of interaction between the talk, the mental, the top and the bottom up, the pharmacological come together in some unique articulation of those layers being coordinated, and that is an example of an emergent mental state coming, being manipulated and being somehow effective in the cure. Now, with the bottom-up processes. Now, how that works is not known. We know phenomenologically all kinds of events like this, but we don't know how it works.

Paulson: And I guess the other question then is, is there some way that if we achieve a certain mental state, if we think a certain way, does that actually rewire the brain?

Gazzaniga: Well, I don't think you have to talk about rewiring, although many people do, I would think you could simply say that by having a developing, a new belief about something, would have a brain state that is influencing lower systems and that sort of activity is, maybe it's another way saying what you're saying as I think about it, but that is a real thing. Let me give an example from neurosurgery. So you can have a patient awake, as you know, during neurosurgical procedures, and you can place an electrode in the olfactory bulb, the part of the brain responsible for smell, and then you can be talking to the patient and you can get them on a positive topic, something pleasant, and you stimulate the olfactory bulb unbeknownst to the patient, and the patient will suddenly say: "oh, who brought in the roses to the room", or something like that. Then, later on, same patient, same electrode, same stimulus parameters and all the rest of it, you can be moving on to an unpleasant topic, and then you stimulate the same kind of stimulus, and the patient all of a sudden interrupts their thoughts, says "oh, who brought the rotten eggs into the room?". So you have these fascinating mental states influencing what, you know, crudely, but seemingly seems to be an identical bottom-up stimulus. So it's those kinds of things that really get you thinking about how these two layers interact, and why that's the question.

Paulson: I know when people talk about emergence, or the mind as an emergent phenomenon, sometimes the talk about the whole being greater than the sum of the parts. In other words, if you just sort of try to add up, you know, all the different neurons, the neural connections, you're not going to explain something at a higher level of organization.

Gazzaniga: Right. And, that is an idea that's been widely discussed and talked about, you cannot predict the properties of the layer above you by a full analysis of the elements that produce it, that's generally what is meant by an emergent property. There's examples of that through all of biology, and many areas of science and, you know, analysis of how processes work.

Paulson: Do we know what makes the human brain different from brains of the rest of the animal world? I guess another way of putting this would be, is the human brain qualitatively different or is it just a little different from, let's say, the brains of our closest relatives, the chimpanzee?

Gazzaniga: So this is a question that a lot of people have taken shots at, and thankfully, meanwhile science moves on and is collecting information, and there are clearly areas of the human brain that have a unique organization. You can spot them in, as early in the processing chain as in the visual cortex, there are areas in the frontal lobe that seem to be unique in the human, that are vanishingly small or not present in the chimp, and that kind of thing. There's this big size difference too, of course, and yet, whether the size is relevant or whether it's kind of a red herring because we humans do so many more things, we're so socially adapted, we control our lives through social rules and all the rest of it that, maybe, that just takes all this other space for all that processing and it's not, that's not the key thing that allows us to think beyond what is present in the environment, which is the big trick between humans and chimps, when we see, chimps understand and can think clearly about things that are in their immediate presence, and we humans can think, or try to think clearly about things that aren't, obviously, in our presence, they're out in the physical mental space.

Paulson: So, it's the capacity for abstract thought, is that what you're talking about?

Gazzaniga: Yeah, that's basically the capacity for abstract thought.
Paulson: And is there a particular part of the brain that has that function?

Gazzaniga: There are, there's lots of, you go into specific tests and have to look at each one, but basically, the abstraction ability seems to be a big feature of the left hemisphere.

Paulson: And it would seem that, as you were just implying, a big difference between human and chimpanzees is that people have a much greater capacity for social interaction with far more people, and somehow our brain seems wired to be very social.

Gazzaniga: That's right, I mean, when you think about it, we humans, what do we think about, ninety-nine percent of the time? It's social relations, right? You're thinking about the intentions of others, you're thinking about your family, you're thinking about what your boss, you're thinking about your girlfriend, your boyfriend, whatever it is. We're always thinking and calculating the social relations of a group, because we want to understand their intentions with respect to us, and all that. So that, the extent of being aware of the social world, and the social groupings you have, some people suggested that that correlates better with brain size than actual thought itself.

Paulson: Do you think that was the, sort of, evolutionary imperative for why we became human was to be able to have more sophisticated social relationships?

Gazzaniga: Oh, I wouldn't put it that way. I don't know if there's anybody in the driver's seat here trying to get to a point.

Paulson: But I mean, there are these fascinating questions about, so, you know, why did our early hominids develop such sophisticated brains and, to take that even one step further, why did Homo Sapiens survive, while the Neanderthals died out?

Gazzaniga: Yeah, those are all great questions. There's just a bunch of things to work through there, and the whole growth of us into a sedentary society, the forming of social groups which had a huge impact on food an fortification... There's just a huge story that's associated with the change of the hominid in... I don't know, I'm not thinking about it right now, I'm thinking about these other things, so...

Paulson: Well, okay, let me follow up on more of the topic of your new book. You've tackled the old question of free will, whether we actually have free will in what would seem to be, in many ways, a deterministic universe. So, how do you break that down, do we have free will?

Gazzaniga: I think it's an arcane concept that seems just out of place, given the modern knowledge of what we're discovering about how the brain works. It's not needed, it has no utility to our understanding of things. What the brain is is a great big information processing device that has with it many features, one of which is this interpreter that creates the illusion that we're in charge and acting freely of our own choice, right? I mean, that's just what it does, it does it in all of us and we all experience it, and that's that. But if you actually understand, begin to understand how the brain works, you find that that's just not what's at stake here, and we should move on to thinking about other issues, and for me, the importance of the concept of, that people thought was so important with the concept of free will is the question of personal responsibility. I say that, what I'm arguing is that the place to look for the answer to what responsibility is, is not in the brain, but it's in the social group. One way to kind of come at it is that if you're the only person in the world, the idea of personal responsibility doesn't mean much. You're responsible to others, and so, when we move into the social group, what we're doing is we're now having a relationship with other people and we have rules and laws and what-have-you. And so, that's where we look for responsibility, and people can follow rules in ninety-nine point nine nine nine percent of cases, so we look for responsibility there, we don't look for it in the brain.

Paulson: But there are real questions about whether if someone has had a damaged brain in some way, there's some part of the brain that's become impaired, and they seem to be naturally more aggressive, more violent, or, if there is retardation, should we hold those people as morally responsible if they commit some crime?

Gazzaniga: I think we hold them responsible, and then I think we move on to the question about what do we want to do about it. And that is a huge social question that we need to talk about, for instance, we should have a category of legal judgment where we say the person is guilty, responsible, and insane. We shouldn't have not guilty by reason of insanity. That's confusing the layers and levels of description here. So, I think that the task is to... You're on the safer side by saying we're all responsible, we all can follow rules, and then, once we decide he's the agent of the crime, he's the person that did the antisocial act, then we decide what we want to do about it. Do we want to treat, do we want retribution, punishment of some kind? Do we want just social isolation? What do we want to do? And that's a very intense and difficult but important debate to have, and I think we should focus on that as the question.

Paulson: But I want to come back to this paradox that you have raised in the way you have put it in your book, you say: we are personally responsible agents and are to be held accountable for our actions, even though we live in a determined universe. Because it would seem that if we live in a determined universe, then we're in some way, we're not responsible anymore.

Gazzaniga: Yeah, and again, so we have, the metaphor I've used is, cars are determined devices and yet, understanding them helps us in no way to understand traffic, when they start to interact. That's a different level of organization and description of an event that 's going on. I would similarly say brains are automatic, but people are free. When brains start to interact, there's a level of relationships, there's a social ether that's created, and that ether can be, you can be held accountable to play by the rules of that new level of organization.

Paulson: It sounds like you're saying that everything's not determined then? We don't live in a deterministic world?

Gazzaniga: Well, I don't see it that way. The brain is determined, but people are to be held responsible for their actions, and that's to say, prize outcome that we humans want to have.

Paulson: Are these kinds of issues that we've been talking about, consciousness, free will, are these basically scientific questions now, or are they still ultimately philosophical questions?

Gazzaniga: Well, you know, I think as science moves on, and more knowledge is gained, science will have a lot to say about it. I mean, the full answer to all these questions of course is way off in the future, but to say that we now appreciate that the brain has mechanisms that work in particular ways, that produce so much of our mental and cognitive life, that's new and I think should give people a good feeling about understanding, about how we function, and it's going to get deeper and deeper and deeper, but where I see it, no matter how far we get into that, we're still going to have this fact that when you talk about responsibility, it's the social interaction.

Paulson: If you could pinpoint one question that you would most liked answered in the study of neuroscience, what would it be? What are the big question, or the big two questions that you are really trying to unpack?

Gazzaniga: Alright, so, this brings us right up to the present, right when I was spending the rest of my time thinking about. Traditional neuroscience thinks there's this linear causal chain. A produces B, which produces C, and so forth, right? What I'm suggesting is there is, really, how to think about it is there's this layered system, where it's not that A produces B, A and B are in a relationship with each other, one layer above the other. And so, when you want to think about the processes going on in the middle of it, you have to think of that interaction of A and B, not that A produces B and that's the end of the story. So, it's figuring out how those layers interact, which is a deep deep problem in science, working it all kinds of levels in science, how those layers interact, how those protocols are going to work between the layers, that's the scientific question of the next generation and the one after it, but I think that's where we're going to have to go if we're going to come to a more full understanding of how brain enables mind.

Paulson: One final question. Are there certain aspects of the mind that you think are just beyond the capacity of science ever to explain?

Gazzaniga: Oh, I'm a hopeless optimist. I want everything on the table.

Paulson: You want everything, but just you know looking into your crystal ball do you think at some point many generations from now science will totally explain how the mind works?

Gazzaniga: Totally explain? I don't know about totally explain but it will be incredibly more clear a hundred years from now than it is today.

Paulson: Okay we'll leave it there. Thank you.

Gazzaniga: Thank you!

Comments for this interview

meaning (falk burger, 11/18/2012 - 6:14pm)

Steve Paulson continues to demand religious answers from scientific minds. One after another, they evade his simplistic questions, many delivering gentle (remember, they're promoting books) rebukes that fall on Steve's science-deaf ears. He wants meaning, explanations! We are at an exciting juncture of science and philosophy, of subjective inquiry (meditation) and inductive inference through experimentation. Without illusion, no meaning, the lamas tell us. The self is illusion, they claim, and science agrees. What could be more marvelous? The paradox here is that in his insistence on a straight answer, Steve's thinking has become more linear and deterministic than the scientists he seems to be trying to ensnare with his clever Socratic queries. The scientists are fine with The Mystery, it does not bother them; it's reassuring in a way to know they will always have job security. Don't bother the bricklayer about the soul of the city, he has a job to do. On This American Life, there was an anecdote about a mathematician who spent 20 years' worth of Sundays, performing millions of calculations, each one a failure, until he performed the one that disproved the theorem. It's not all fireworks; The Mystery abides, poking and prodding it avail nothing, yet the soul of the city grows.