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DAVE DAVIES, Host:

This is FRESH AIR. I'm Dave Davies, filling in for Terry Gross, who has the week off.

Our guest, neuroscientist Dean Buonomano, says the human brain is a pretty amazing piece of technology: 90 billion neurons connected by 100 trillion synapses. But he says while it's capable of extraordinary things, like analyzing the features of a human face for instant recognition or doing the calculations necessary to catch a fly ball on the run, it can be pretty dumb in other ways.

We're not naturally good at quantitative thinking, for example, Buonomano says many of these weaknesses are a product of our evolution. Our ancestors needed to recognize a dangerous animal quickly but didn't need to know whether there were 12 or 13 of them.

Buonomano's new book looks at some of the ways our brains' peculiar adaptations affect our behavior in a world very different from that of our prehistoric ancestors. He thinks they help explain why we invent false memories, fall prey to advertising tricks and make irrational financial decisions. His book is called "Brain Bugs: How the Brain's Flaws Shape Our Lives."

Well, Dean Buonomano, welcome to FRESH AIR. You make the point in this book that our brains evolved to adapt to a time that's very, very different from the days that we live in, and therefore in some respects our brains don't function as well as we'd like for modern times. Just give us a simple example.

DEAN BUONOMANO: Well, the basic point here is precisely as you said, that we evolved for a different place, one in which we no longer live in. Perhaps I could give an example from another animal, and that would be a skunk, for example.

Skunks have a very powerful defense mechanism, in which when they're attacked, they turn around, lift their tails and spray, and this has suited them well throughout evolution.

Today, however, that's not that good of an idea if they're facing an oncoming car because they didn't evolve to deal with that circumstance. And humans suffered some of the same consequences of living in a time and place we didn't evolve to live in.

One example is in relationship to numerical calculations, numbers. Evolutionarily speaking, of course there wasn't much pressure to manipulate numbers, to calculate logarithms.

DAVIES: Now, you say that our brains evolved in an era when there wasn't much need for, you know, mathematical computation, for a sharp sense of quantitative thinking. Why? Give us an example.

BUONOMANO: The brain is very good at pattern recognition. And the fact that we currently use numbers in order to quantify anything from baseball scores or our salaries, there wasn't many situations in which that was required in the past. People weren't negotiating. They weren't making transactions.

They were judging whether something was dangerous or not. There wasn't a need or the ability to manipulate symbols. So I think in the case of numerical calculations, there wasn't that many circumstances in which animals will benefit from manipulating numbers, from doing long division and so forth.

But even if there had been pressure, the building blocks of the brain probably weren't very well-suited for that function.

DAVIES: You note that we don't have a sense of what numbers really mean intuitively. We don't have a sense of fourness or fiveness in the same way that we can look at a friend and gather a lot of information about, you know, the shape of their eyes and nose and smile and immediately kind of integrate this and recognize a face.

And you say this is related to the associative architecture of the brain. Explain what that means.

BUONOMANO: When we recognize a pattern, and I look at your face, part of the task is to grasp the whole from the sum of the parts. And because neurons are very social, and they're communicating with our neurons near and far, that allows them to communicate with each other and provide a picture of the whole and provide a context.

So perhaps it's a bit easier to understand in distinguishing the brain's ability to pick up context and the computer's ability to pick up context.

If you hear somebody say Johnny fell off the wagon, if you hear that sentence in a playground or in the bar, it means very, very different things, yet your ability to pick out those different meanings is totally automatic because your visual system is communicating with your language centers. Your visual system is providing the context precisely because neurons are well-suited to share that information, unlike the transistors on the computer.

DAVIES: And I was fascinated in the explanation that you give of how this association of information works in the brain. There are billions of neurons, right?

BUONOMANO: Absolutely.

DAVIES: And neurons connect to other neurons through these connections called synapses and that when we have a concept, this is a node which consists of connections among many, many neurons.

And like for example, my son told me about a terrific new ice cream when we went on vacation recently, I'd never known it, chocolate pretzel ice cream. And so probably now in my brain - stop me if I'm making an idiot of myself or getting this wrong - but there's this node now for chocolate pretzel ice cream in which it connects a lot of neurons which already exist.

I already knew about chocolate. I already knew about pretzel, but now this is associated with chocolate with pretzel with terrific memories and tastes in my mind and chocolate fudge and vanilla. And when I think about this, these neurons, the connections between these neurons fire, and the connections is thereby strengthened, and just by talking to you now about it, these connections among these neurons that amount to chocolate pretzel ice cream are being strengthened.

DAVIES: So we have these associations all over the brain, right?

BUONOMANO: Correct, and so this is a good example. So you previously had some group of neurons in your brain representing chocolate and others representing pretzel. And perhaps you had no reason to link those in the past. And now that your son has pointed out this delicious new delicacy, maybe you do.

So the brain somehow manages to connect concepts that occur together, and typically this is referred to in the little axiom: Neurons that fire together wire together.

So if you hear that chocolate and pretzels make a good ice cream, and you now discuss that, you share that with your friends, those neurons are being activated at more or less the same time, and somehow the notion is, is that the neurons representing each one of those concepts comes to be connected to each other.

And that's how the brain stores information. So in the same way that websites that share similar topics are linked to each other, concepts within our memory that are somehow related to each other have links. The synapses between them share information.

DAVIES: So let's talk a little bit about how that pattern of association and connection affects our behavior. I mean, you have some interesting experiments in the book that demonstrate this.

BUONOMANO: So can I give an example first in memory? So can I ask three questions?

DAVIES: Sure.

BUONOMANO: So the three questions are - they're not trick questions. I'm just going to ask two of the questions, and just go ahead and answer, and the third one is a free association. You're just going to answer the first thing that pops into your head.

And the first question is: In what continent is Kenya?

DAVIES: Africa.

BUONOMANO: What are the two opposing colors in the game of chess?

DAVIES: Black and white - I almost said red and white. That was - I'm a checkers guy.

(SOUNDBITE OF LAUGHTER)

BUONOMANO: Fair enough. Think of any animal.

DAVIES: A zebra.

BUONOMANO: So here, many people will think of zebra. Of course not everybody will think of zebra, but by priming your memory towards Africa and black and white, I increased the likelihood people will think of zebra. So that's because nodes, these groups of neurons representing Africa and black and white, talk to each other. They contaminate each other's activity.

And as you said, this goes beyond what we're thinking. And it turns out that this can also affect our behavior. And because there's always cross-talk going on in the brain. And one of the examples from some investigators who were at NYU at the time, they performed a study in which they asked the subjects to do word puzzles, to make sentences with a lot of words that were biased towards being very polite or nice or kind and another group that used words that were biased towards being rude or impolite, impatient and so forth.

And the subjects in the study thought that that was the point of the study. After they finished this task, they were told to go over and talk to one of the assistants who was pretending to be on the phone. And the real measure was how long they waited before they interrupted the ongoing phone conversation.

And it turns out that the people who did word puzzles that were more heavily populated with rude words actually waited less to interrupt the ongoing conversation than those who were doing word puzzles with polite words. So this is sort of an example of behavioral priming in which the words have the ability sometimes to influence our thoughts.

Many other studies shared the similar findings in that if I asked people - if people are asked to think about the future, it turns out they lean imperceptibly forward a bit. If they're asked to think about the past, they lean imperceptibly backwards a bit because of the crosstalk that neurons provide.

And even our memories are somehow linked to our emotions and to our actions and our behaviors. The brain, unlike a computer, is not compartmentalized. Everything is talking to everything else.

DAVIES: Just by thinking about the words, say, courtesy and patience might make me a little more inclined to be courteous and patient in my conduct because these nodes are firing, and the words are connected with behavior.

BUONOMANO: When you think of the future, we normally think about that as forward, and forward is also associated with movement forward. So when you think about the future, maybe some of the neurons involved with motor control, because they've been linked in the past with movement forwards, are slightly tickled and drive people's movement a bit forward.

Now, I want to make it clear that these are subtle effects.

DAVIES: Right, but it is fascinating, though. One of the other examples I loved was that in some experiments, people were more inclined to describe someone's personality as warm if they had been holding a warm cup of coffee as opposed to a cold drink. Again, the association with warmth, it had connections.

I mean, a computer might think of warm as one discrete thing, but in our brains, it can mean a lot of things. It can mean a pleasing personality, as well as something which is hot to touch.

BUONOMANO: Absolutely.

DAVIES: We're speaking with neuroscientist Dean Buonomano. His new book is called "Brain Bugs." We'll talk more after a break. This is FRESH AIR.

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DAVIES: If you're just joining us, we're speaking with neuroscientist Dean Buonomano. He has a new book called "Brain Bugs: How the Brain's Flaws Shape Our Lives."

You have a fascinating discussion of memory and how it works or doesn't work so well. A lot of us struggle with inadequate memory at times. First of all, give us some examples of corrupted memory. And there were some cases here with, you know, quite serious consequences.

BUONOMANO: One type of memory error that we make, a memory bug, is really a product of the fact that in human memory, there's no distinct process or distinction between storage and retrieval.

So when a computer or a DVD writes something down, it has one laser that's used to store the memory, and it has another laser to retrieve the memory, and those are very distinct processes.

Now, in human memory, the distinction between storage and retrieval is not very clear, and this can have very dramatic consequences. So one of the cases I discuss in the book was in the situation of eyewitness testimony, and here there was a woman, her name is Jennifer Thompson(ph), who has actually written a book about her experience.

And she had been raped, and during her ordeal, she had made a conscious effort to try to memorize the face of her assailant. Later on that day, she identified a person as her assailant in the police station's photo lineup, and eventually that person was convicted of rape and sentenced to life in prison, and he ended up spending 11 years in prison.

It later became clear that she did not identify the correct person. She identified somebody who looked like him. And the reason this happened was probably because she had a partial image, a partial memory, of her true assailant. In looking at a series of pictures in which her true assailant was not present, she merged, she overwrote part of the original memory.

Because the operation of storage and retrieval are not totally independent, the act of retrieving a memory can also affect the storage.

DAVIES: So how is that related to the associative architecture of the brain the way that a subsequent encounter or experience can actually edit a memory that we have?

BUONOMANO: So this is - probably shouldn't be seen as directly related to the associative architecture of the brain. This should be seen as a consequence of the fact that memory is written down as we experience it. It's being continuously updated. And the synapses that undergo changes in strength - so as you alluded to earlier, one of the ways the brain writes does information is by making new synapses, making new connections or strengthening new ones or weakening old ones.

And that process uses these synapses that get strengthened, but the retrieval also uses those same synapses. So that can strengthen that pathway.

And this can be very useful, for example, if every time you see your cousin, and from - in six months intervals, he will look a bit different. You don't have a perfect memory of him five years and then four years ago and then three years ago. Your memory of him is always being updated every time you see him. It's being adjusted. It's being fine-tuned. So that's a very valuable characteristic of human memory because we update the dynamic images that we see in the world.

But this was very bad in Jennifer Thompson's case in that she didn't have a well-formed memory, and during the updating process, she apparently updated it to a different individual altogether.

DAVIES: Let's talk about time. How are our perceptions of time shaped by our evolutionary history?

BUONOMANO: When we're talking about time, it's very important to stress that time is absolutely critical for everything we do and over many scales. And it's well-illustrated by the conversation we're having right now in that we're using each other's pauses to - in order to tell when you've finished your question or when I can interrupt.

DAVIES: He gave her cat food. That will be interpreted differently if I say if I gave her cat food because that difference in meaning there was primarily transmitted in the pause. So your brain is implicitly paying - and automatically paying attention to this and has some sort of timer that allows it to figure this out.

But when we think of the perception of time, most people think of the subjective sense of time: How long have they been listening to this program, how long are they stuck in traffic? And the brain seems to have multiple different mechanisms, and that's one thing that we've learned about how the brain tells time is that unlike the clocks on our wrist that can be used to tell a few milliseconds or months and years, the brain has very fundamentally different mechanisms for telling very short periods of time and very long periods of time.

And that's a consequence of the evolutionary process, that it came up with redundant solutions and different solutions depending upon the adaptive needs of different animals.

And it turns out that we don't seem to have a very precise clock. Time is very much distorted when we are anticipating what's about to happen, when we're nervous, when we're stressed and when we have high-adrenaline moments. Our internal clock is not that accurate.

DAVIES: Our ancestors grew up in a world in which they didn't think about the future in the way that we do, right. I mean, nobody was preparing for their SATs or college when they were living in caves. Did that affect our sense of time in that are we more likely to focus on the immediate, the present, than to plan ahead?

BUONOMANO: Yes, the issue of long-term planning is a fascinating one, and we do have a very strong immediate bias or immediate gratification bias. As you said, primitive man probably wasn't planning for their SATs or their retirement pension plan.

This makes sense of the context of other animals, that we inherited much of our neural ware from. So this is typically exemplified if I give you a choice. You have one option, which is to receive $100 now, or in a month from now, you'll receive $120.

Here, most people choose the $100 now because that provides an immediate reward, of sorts, although economists would argue that the rational choice there is to wait the extra month for the $20.

Now this bias makes a lot of sense, of course, evolutionarily speaking. If I offer you an apple now and two apples in a month from now, and you're hungry now, it does not make any sense to wait the extra month because immediate survival is always the priority, and we see this in both ourselves and our animal ancestors.

DAVIES: Dean Buonomano is a professor in the Departments of Neurobiology and Psychology and the Brain Research Institute at UCLA. His new book is called "Brain Bugs." He'll be back in the second half of the show. I'm Dave Davies, and this is FRESH AIR.

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DAVIES: This is FRESH AIR. I'm Dave Davies in for Terry Gross. We're speaking with UCLA neuroscientist Dean Buonomano. He says our brains are adapted to a prehistoric world very different from our own, for generating blind spots and weaknesses that affect the way we think and behave. His book is called "Brain Bugs: How the Brain's Flaws Shape Our Lives."

You have a chapter called "The Fear Factor." Has evolution conditioned us to fear some threats more than others?

BUONOMANO: Yes. Our neuro-operating system, if you will, the set of rules were endowed in our genes that provide instructions on how to build the brain, what it should come preloaded with, the innate biases we should have, and most animals have innate biases to fear predator with big sharp teeth and to fear poisonous spiders and poisonous snakes. Because those innate fears increase survival. And you don't want to have to learn to fear snakes because you might not have a second chance. So we still carry that genetic baggage within our neuro-operating system.

It's safe to say that it's outdated. We currently live in a world in which in the United States, probably few people a year die or suffer severe consequences due to snake bites. But every year 44,000 people die of car accidents. So in the same way that evolution did not prepare say skunks to cope with the dangers of automobiles, evolution did not prepare humans to face the dangers of many of the things that surround us in our modern life, including automobiles, or an excess fluid for example of that we deal with problems due to obesity and too much cholesterol are all things that now have very dramatic effects on our lives, and we weren't prepared for those things by the evolutionary process.

DAVIES: Our ancestors would eat as much as they could as often as they could, because they didn't know when the next meal would be there.

BUONOMANO: It's very important to get as much fat as you could.

DAVIES: Your book cites a lot of cases where we're pretty bad at decision- making, and particularly in cases that involves relatively simple calculations of what the most favorable options would be. Give us an example of one of those and tell us what's going on.

BUONOMANO: A lots of our decisions are the product of two different systems interacting within the brain. And very loosely speaking, you can think of one of these as the automatic system, which is very unconscious and associative and emotional; and people can think of this as intuition. And then we have the reflective system, which is effortful, requires knowledge and careful deliberation. And people can get a quick feel for these two systems in operation with the following examples. The old trick question: what do cows drink? The part of your brain that just thought of milk was the automatic system. And then the reflective system comes in and says wait a minute. That's wrong. The answer is water.

DAVIES: I'm going to throw four coins up in the air what's the probability that two of them will be heads and two of them will be tail? Now, part of the brain that's just thinking of well, it sounds like it should be 50 percent, because I said half the coins tails, half the coins heads. That's again basically the automatic system. It would take the reflective system, some serious reflection, to work out the math and come up with an answer of six- sixteenths.

Now, in most cases we reach happy balances between both of these systems. And clearly, when we are understanding each other's speech and making rapid decisions, the automatic system provides great balance as to what the proper answer is. But when we need to engage our reflective system and ask questions, such as the probability question that I just asked, sometimes we are misled because we trust the automatic system too much and the reflective system doesn't really get through in some situations. And this can lead us, in the case for example, of the temporal discounting situation where I asked if you want $100 today or $120 in the future. So the automatic system, which is biased by immediate gratification, might get the edge in that situation.

DAVIES: Since you spent so much time studying and thinking about how the brain works and how it's, our intuitive or automatic responses might not be the best and we need to be more reflexive and rational, do you go around analyzing the way you react to things?

BUONOMANO: Probably a bit too much. Yes. I do and I certainly have been known to annoy the people around me, perhaps because I do that a bit too much. But as far as our own brain bugs go, there's an abundance of them and I certainly think that that is just one of the many that I tried to take into account when I'm making decisions, particularly important decisions, of course.

DAVIES: Do you have a good retirement account?

(SOUNDBITE OF LAUGHTER)

BUONOMANO: I hope so.

DAVIES: Well, Dean Buonomano, thanks so much for speaking with us.

BUONOMANO: Thank you very much. It's been a pleasure.

DAVIES: Dean Buonomano is a professor in the departments of neurobiology and psychology and the Brain Research Institute at UCLA. His new book is called "Brain Bugs: How the Brain's Flaws Shape Our Lives."

Coming up, Brian Chen talks about living in a world of smartphones. His book is called "Always On."

This is FRESH AIR.

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