WEBVTT - Ep30 "What does it mean to know thyself in the age of neuroscience?" Part 2 0:00:05.080 --> 0:00:08.600 Can we explain our consciousness just by looking at the 0:00:08.720 --> 0:00:12.360 molecules in our brain? How is the color of your 0:00:12.520 --> 0:00:17.840 passport related to whether you get schizophrenia? Males are more 0:00:17.880 --> 0:00:22.080 predisposed to commit crime, so why don't all males commit crime? 0:00:22.520 --> 0:00:24.000 And what does any of this have to do with 0:00:24.160 --> 0:00:28.160 traffic jams, or why Seinfeld is funny? Or how we're 0:00:28.200 --> 0:00:33.000 ever going to come to know ourselves from studying our biology. 0:00:36.400 --> 0:00:40.080 Welcome to the Inner Cosmos with me David Eagleman. I'm 0:00:40.120 --> 0:00:43.680 a neuroscientist and an author at Stanford and in these 0:00:43.720 --> 0:00:47.519 episodes we sail deeply into our three pound universe to 0:00:47.680 --> 0:00:59.960 examine the intersection of our brains in our lives. Today 0:01:00.200 --> 0:01:04.760 episode is part two of the question of knowing Thyself. 0:01:05.160 --> 0:01:07.959 So last week we talked about how we know with 0:01:08.120 --> 0:01:13.040 certainty that our consciousness our essence is tied to our 0:01:13.080 --> 0:01:17.800 biology and the possibility that we are nothing but our biology. 0:01:18.520 --> 0:01:22.240 In this episode, I want us to expand our imagination 0:01:22.480 --> 0:01:27.000 even more and consider ourselves in the context of people 0:01:27.440 --> 0:01:30.640 not at the conclusion of science's journey, but instead is 0:01:30.720 --> 0:01:34.480 people just some distance along the path who are facing 0:01:34.640 --> 0:01:37.800 hundreds or thousands of years of research ahead. Of us, 0:01:38.480 --> 0:01:41.840 and specifically, I want to be clear eyed about the 0:01:42.040 --> 0:01:47.440 challenges and possibly the impossibility of trying to explain our 0:01:47.520 --> 0:01:52.480 experience of life in terms of the interaction of molecules. 0:01:53.120 --> 0:01:56.440 So in this episode, we're going to talk about levels 0:01:56.480 --> 0:02:05.360 of understanding and what a meaningful explanation would look like. Okay, 0:02:05.440 --> 0:02:09.160 so you remember the Human Genome project, in which our 0:02:09.240 --> 0:02:15.080 species successfully decoded the billions of letters long sequence in 0:02:15.160 --> 0:02:19.760 our own genetic cookbook. Now, that project was a massive 0:02:19.919 --> 0:02:24.160 landmark achievement for us, and almost everyone has heard of 0:02:24.200 --> 0:02:27.880 the Human Genome project, but not everyone knows that in 0:02:28.000 --> 0:02:32.560 some ways the project was a failure because we sequenced 0:02:32.639 --> 0:02:36.400 the whole code, but once we got there, we didn't 0:02:36.560 --> 0:02:41.720 find the hoped for breakthrough answers about the genes that 0:02:41.760 --> 0:02:46.080 are unique to humankind. Instead, what we discovered was a 0:02:46.240 --> 0:02:50.000 massive recipe book for building the nuts and bolts of 0:02:50.040 --> 0:02:55.320 biological organisms. We found that other animals have essentially the 0:02:55.360 --> 0:02:58.160 same genome that we do, and this is because they 0:02:58.160 --> 0:03:00.800 are made of the same nuts and bolts, only in 0:03:00.919 --> 0:03:06.120 slightly different configurations. The human genome is not terribly different 0:03:06.160 --> 0:03:10.280 from the squirrel genome or the tunafish genome, even though 0:03:10.400 --> 0:03:14.680 humans are terribly different from squirrels and tunafish. At least, 0:03:14.960 --> 0:03:18.400 humans and these other animals seem quite different at first, 0:03:18.760 --> 0:03:22.160 but keep in mind that all of them require the 0:03:22.280 --> 0:03:27.160 recipes to build eyeballs and spleens and skin and bones 0:03:27.200 --> 0:03:30.840 and hearts and so on, so as a result, the 0:03:30.960 --> 0:03:36.280 genomes are not so dissimilar. Imagine going to different factories 0:03:36.320 --> 0:03:40.000 and examining the pitches and lengths of the screws that 0:03:40.040 --> 0:03:42.920 are used. This would tell you very little about the 0:03:43.000 --> 0:03:46.320 function of the final product. Say if it's a toaster 0:03:46.560 --> 0:03:51.520 versus a blow dryer, both assemble similar elements to achieve 0:03:51.720 --> 0:03:55.680 different functions. Now, the fact that we didn't learn what 0:03:55.760 --> 0:03:58.480 we thought we might is not a criticism of the 0:03:58.560 --> 0:04:02.640 human genome project. It was an enormously important first step. 0:04:02.960 --> 0:04:07.400 But what this does tell us is that successive levels 0:04:07.440 --> 0:04:11.120 of reduction are typically going to tell us very little 0:04:11.520 --> 0:04:16.920 about the questions important to humans. So in the last episode, 0:04:16.960 --> 0:04:21.440 we introduced this question of whether we can understand ourselves 0:04:21.520 --> 0:04:26.440 by an approach called reductionism. Reductionism is the idea that 0:04:26.480 --> 0:04:31.160 we can successively reduce the problems down to their small 0:04:31.360 --> 0:04:35.760 scale biological pieces and parts, and eventually come to explain 0:04:36.279 --> 0:04:43.120 complex phenomena like thinking and consciousness by understanding the molecules. Now, 0:04:43.160 --> 0:04:46.120 there's been a lot of excitement about this possibility for 0:04:46.160 --> 0:04:50.320 a long time in neuroscience. For example, in the last episode, 0:04:50.360 --> 0:04:54.479 I mentioned Huntington's disease, which is a disorder that's caused 0:04:54.480 --> 0:04:57.679 by a mutation in a single gene, and in fact 0:04:57.839 --> 0:05:01.160 it was the first gene pulled for a disease, which 0:05:01.160 --> 0:05:05.479 seemed like a great success story for reductionism. If you 0:05:05.600 --> 0:05:09.320 have this gene, you'll get this disease. But note that 0:05:09.520 --> 0:05:13.800 Huntington's is one of the very few examples that can 0:05:13.839 --> 0:05:17.400 be dredged up for this sort of one to one mapping. 0:05:17.880 --> 0:05:21.760 The reduction of a disease to a single mutation is 0:05:21.839 --> 0:05:28.839 extraordinarily rare. Most diseases are polygenetic, meaning that they result 0:05:29.000 --> 0:05:34.160 from subtle contributions of tens or hundreds of different genes, 0:05:34.839 --> 0:05:38.880 and as science develops better techniques, we're discovering that not 0:05:39.040 --> 0:05:42.440 just the coding regions of the genes matter, but also 0:05:42.520 --> 0:05:45.359 the areas in between what used to be thought of 0:05:45.400 --> 0:05:50.680 as junk DNA. Most diseases seem to result from a 0:05:51.000 --> 0:05:57.120 perfect storm of numerous minor changes that combine in dreadfully 0:05:57.320 --> 0:06:03.479 complex ways. The challenge to reductionism is far worse than 0:06:03.560 --> 0:06:08.040 just a multiple genes problem. The contributions from the genome 0:06:08.120 --> 0:06:13.159 can really be understood only in the context of interaction 0:06:13.360 --> 0:06:19.360 with the environment. So consider schizophrenia, a disease for which 0:06:19.520 --> 0:06:23.440 teams of researchers have been gene hunting for decades. Now 0:06:23.440 --> 0:06:27.279 have they found any genes that correlate with the disease? 0:06:27.880 --> 0:06:31.960 Sure they have hundreds. In fact, does the possession of 0:06:32.040 --> 0:06:35.040 any one of these genes offer much in the way 0:06:35.120 --> 0:06:39.120 of prediction about who will develop schizophrenia as a young adult. 0:06:39.920 --> 0:06:44.800 Very little. No single gene mutation is as predictive of 0:06:44.839 --> 0:06:49.960 schizophrenia as the color of your passport. What does your 0:06:49.960 --> 0:06:53.320 passport have to do with schizophrenia? It turns out that 0:06:53.440 --> 0:06:57.360 the social stress of being an immigrant to a new 0:06:57.440 --> 0:07:01.600 country is one of the critical factors in developing schizophrenia. 0:07:02.080 --> 0:07:06.679 In studies across countries, immigrant groups who differ the most 0:07:06.720 --> 0:07:10.880 in culture and appearance from the host population carry the 0:07:11.040 --> 0:07:15.360 highest risk of schizophrenia. In other words, a lower level 0:07:15.440 --> 0:07:20.240 of social acceptance into the majority correlates with a higher 0:07:20.360 --> 0:07:25.240 chance of a schizophrenic break in ways not fully understood. 0:07:25.320 --> 0:07:31.440 It appears that repeated social rejection perturbs the normal functioning 0:07:31.600 --> 0:07:35.680 of the dopamine systems. But even these generalizations don't tell 0:07:35.720 --> 0:07:40.000 the whole story, because within a single immigrant group, say 0:07:40.120 --> 0:07:45.160 Koreans in America, those who feel worse about their ethnic 0:07:45.240 --> 0:07:49.440 differences from the majority are more likely to become psychotic. 0:07:49.720 --> 0:07:53.000 Those who are proud and comfortable with their heritage are 0:07:53.080 --> 0:07:58.480 mentally safer. Now this news comes as a surprise to many. 0:07:59.000 --> 0:08:04.000 Isn't schizophrenia a genetic disorder? The answer is that genetics 0:08:04.200 --> 0:08:08.080 play a role. If the genetics make nuts and bolts 0:08:08.120 --> 0:08:11.440 that have a slightly altered shape, the whole system may 0:08:11.520 --> 0:08:16.760 run in an unusual manner when put in particular environments. 0:08:17.200 --> 0:08:20.280 In other environments, the shape of the nuts and bolts 0:08:20.360 --> 0:08:23.320 may not matter. When all is said and done, how 0:08:23.360 --> 0:08:27.360 a person turns out depends on much more than the 0:08:27.440 --> 0:08:32.080 molecular suggestions written down in the DNA. You may remember 0:08:32.120 --> 0:08:36.000 that in an earlier episode on neurolaw, I mentioned that 0:08:36.240 --> 0:08:39.360 some people have an eight hundred and twenty eight percent 0:08:39.679 --> 0:08:44.240 higher chance of committing a violent crime if they carry 0:08:44.280 --> 0:08:48.079 a certain set of genes. And those genes you may 0:08:48.120 --> 0:08:52.439 remember are summarized as the Y chromosome. If you are 0:08:52.520 --> 0:08:56.719 a carrier, we call you a male. Now that correlation 0:08:57.000 --> 0:09:00.640 between the Y chromosome and crime is fact, But the 0:09:00.720 --> 0:09:05.280 important question to ask is this, why aren't all males criminals? 0:09:05.320 --> 0:09:08.559 In fact, there's only one percent of males that get incarcerated. 0:09:09.000 --> 0:09:12.640 So what's going on the answer is that knowledge of 0:09:12.760 --> 0:09:16.640 the genes alone is not sufficient to tell you much 0:09:16.679 --> 0:09:21.920 about behavior. Consider the work of Stephen Swomy. He's a 0:09:22.040 --> 0:09:26.880 researcher who raises monkeys in natural environments in Maryland. Now, 0:09:26.920 --> 0:09:31.240 in his natural environment setting, he can observe the monkey's 0:09:31.480 --> 0:09:35.199 social behavior from their day of birth, and one of 0:09:35.240 --> 0:09:37.800 the first things he noticed was that monkeys begin to 0:09:38.360 --> 0:09:43.760 express different personalities from a surprisingly early age. He saw 0:09:43.800 --> 0:09:48.640 that virtually every social behavior was developed and practiced and 0:09:48.679 --> 0:09:53.000 perfected during the course of peer play by four to 0:09:53.080 --> 0:09:56.199 six months of age. Now this observation would have been 0:09:56.240 --> 0:09:59.440 interesting by itself, but Swomy was able to combine the 0:09:59.480 --> 0:10:04.720 behavior observations with regular blood testing of hormones and metabolites, 0:10:04.720 --> 0:10:08.520 as well as genetic analysis. What he found were that 0:10:08.679 --> 0:10:12.920 five percent of the baby monkeys were overly aggressive. They 0:10:13.000 --> 0:10:19.200 showed impulsive and inappropriately belligerent behavior. Those monkeys had low 0:10:19.280 --> 0:10:23.680 levels of a blood metabolite related to the neurotransmitter serotonin. 0:10:24.559 --> 0:10:28.240 Now here's the key. Swomi and his team found that 0:10:28.320 --> 0:10:31.440 there were two different flavors of genes. These are called 0:10:31.480 --> 0:10:36.439 alleles that one could possess for a protein that's involved 0:10:36.440 --> 0:10:39.600 in transporting serotonin. Let's just call these the short and 0:10:39.679 --> 0:10:44.360 the long forms. Now, the monkeys with the short form 0:10:44.559 --> 0:10:48.559 showed poor control of violence, while those with the long 0:10:48.679 --> 0:10:53.520 form displayed normal behavioral control. But that turned out to 0:10:53.559 --> 0:10:57.439 be only part of the story. How a monkey's personality 0:10:57.480 --> 0:11:02.160 developed depended on its environment as well. So there were 0:11:02.200 --> 0:11:06.360 two ways the monkeys could be reared, either with their mothers, 0:11:06.400 --> 0:11:09.920 which was a good environment, or with their peers, which 0:11:10.040 --> 0:11:15.480 was called an insecure attachment relationship environment. So the monkeys 0:11:15.559 --> 0:11:19.280 with the short form ended up as the aggressive type 0:11:19.360 --> 0:11:22.280 when they were raised with their peers, but they did 0:11:22.440 --> 0:11:26.160 much better when they were raised with their mothers. For 0:11:26.240 --> 0:11:29.439 those with the long form of the gene, the rearing 0:11:29.520 --> 0:11:32.400 environment didn't seem to matter much. They were well adjusted 0:11:32.440 --> 0:11:35.720 in either case. Now, there are at least two ways 0:11:35.760 --> 0:11:39.160 to interpret these results. The first is that the long 0:11:39.200 --> 0:11:43.400 allele is a good gene that gives resilience against a 0:11:43.520 --> 0:11:47.160 bad childhood environment. The second way you could interpret this 0:11:47.320 --> 0:11:49.600 is that you have some monkeys who would have turned 0:11:49.640 --> 0:11:52.600 out to be bad seeds, but they were rescued by 0:11:52.640 --> 0:11:56.480 good mothering. Now these two interpretations aren't exclusive, and we 0:11:56.520 --> 0:11:59.760 don't know which one is exactly correct, but they boiled 0:11:59.800 --> 0:12:05.280 down to the same important lesson. A combination of genetics 0:12:05.400 --> 0:12:11.120 and environment matters for the final outcome. So, following on 0:12:11.200 --> 0:12:15.599 from these monkey studies, people started to study gene environment 0:12:15.800 --> 0:12:20.199 interactions in humans. In two thousand and one, a researcher 0:12:20.280 --> 0:12:23.480 named av Shalom Caspi and his colleagues set out to 0:12:23.520 --> 0:12:28.400 ask whether there are genes for depression. When they went 0:12:28.480 --> 0:12:31.640 on the hunt, they found that the answer is sort of. 0:12:32.120 --> 0:12:36.200 They learned that there are genes that predispose you, but 0:12:36.280 --> 0:12:41.599 whether you actually suffer from depression depends on your life's events. 0:12:42.400 --> 0:12:46.440 The researchers discovered this by carefully interviewing dozens of people 0:12:46.480 --> 0:12:50.319 to find out what sort of major traumatic events had 0:12:50.320 --> 0:12:53.600 transpired in their lives. The loss of a loved one, 0:12:53.800 --> 0:12:57.280 a major car accident, and that sort of thing. So 0:12:57.360 --> 0:13:01.840 for each participant, they also analyzed the genetics, specifically the 0:13:01.880 --> 0:13:05.640 form of a gene involved in regulation of serotonin levels 0:13:05.640 --> 0:13:09.880 in the brain. Because people carry two copies of the gene, 0:13:09.920 --> 0:13:14.360 one from each parent, there are three possible combinations that 0:13:14.400 --> 0:13:18.520 someone might carry, a short short, a short long, or 0:13:18.559 --> 0:13:22.360 a long long. The amazing result they found was that 0:13:22.640 --> 0:13:28.960 the short short combination predisposed the participants to clinical depression, 0:13:29.360 --> 0:13:34.160 but only if they experienced an increasing number of bad 0:13:34.200 --> 0:13:37.040 life events. If they were lucky enough to have a 0:13:37.200 --> 0:13:41.320 good life, then carrying the short short combination made them 0:13:41.520 --> 0:13:44.559 no more likely than anyone else to become clinically depressed. 0:13:45.120 --> 0:13:48.360 But if they were unlucky enough to run into serious troubles, 0:13:48.800 --> 0:13:52.160 including events that were entirely out of their control, then 0:13:52.200 --> 0:13:55.400 they were more than twice as likely to become depressed 0:13:55.760 --> 0:13:59.720 as someone with the long long combination. So whether somebody 0:14:00.240 --> 0:14:04.240 sense with depression is a matter of their genes and 0:14:04.360 --> 0:14:24.400 their life circumstances. Now, Caspy's group then did an entirely 0:14:24.440 --> 0:14:29.560 different second study to address a deep societal concern. Do 0:14:30.160 --> 0:14:34.479 children who are abused grow up to become child abusers themselves? 0:14:35.280 --> 0:14:38.560 Many people believe this statement, but is it really true 0:14:39.200 --> 0:14:43.760 and does it matter what kind of genes the child carries. 0:14:44.440 --> 0:14:47.200 What caught the attention of the researchers was the fact 0:14:47.240 --> 0:14:52.200 that some abused children become violent as adults, but other 0:14:52.280 --> 0:14:56.520 abused children do not. When all the obvious factors were 0:14:56.520 --> 0:15:01.040 controlled for. The fact stood that childhood abuse by itself 0:15:01.240 --> 0:15:04.800 does not predict how an individual would turn out. So 0:15:05.040 --> 0:15:09.080 inspired to understand the difference between those who perpetrate the 0:15:09.160 --> 0:15:12.920 violence and those who don't, Caspian his colleagues discovered that 0:15:13.080 --> 0:15:17.120 a small change in the expression of a particular gene 0:15:17.680 --> 0:15:22.200 is what differentiated these two groups. Children with low expression 0:15:22.320 --> 0:15:26.440 of the gene were more likely to develop conduct disorders 0:15:26.480 --> 0:15:31.240 and become violent criminals as adults, but this bad outcome 0:15:31.360 --> 0:15:36.280 was much more likely if the children were abused. If 0:15:36.280 --> 0:15:38.880 they harbored the let's call it the bad forms of 0:15:38.920 --> 0:15:42.960 the gene, but had been spared childhood abuse, they were 0:15:43.040 --> 0:15:46.160 not likely to become abusers. And if they harbored the 0:15:46.560 --> 0:15:49.880 good form of the gene, then even a childhood of 0:15:49.920 --> 0:15:54.680 severe maltreatment would not necessarily drive them to continue the 0:15:54.800 --> 0:15:58.480 cycle of violence. And let me give a third example 0:15:58.600 --> 0:16:01.800 of the interaction of gene an environment, and this one 0:16:01.840 --> 0:16:06.160 comes from the observation that smoking cannabis marijuana as a 0:16:06.240 --> 0:16:12.120 teenager increases the probability of developing psychosis as an adult. 0:16:12.880 --> 0:16:16.320 But this connection is true only for some people and 0:16:16.400 --> 0:16:18.800 not for others. By this point you can guess the 0:16:18.840 --> 0:16:21.720 punch I'm going to say, which is that a genetic 0:16:21.880 --> 0:16:28.440 variation underlies one's susceptibility to this. With one combination of alleles, 0:16:28.760 --> 0:16:32.720 there's a strong link between cannabis use and adult psychosis. 0:16:33.000 --> 0:16:37.520 With a different combination, the link is weak. And here's 0:16:37.560 --> 0:16:42.480 another example. The psychologists Angelos Scarpa and Adrian Rain measure 0:16:42.640 --> 0:16:48.240 differences in brain function among people diagnosed with antisocial personality disorder, 0:16:48.960 --> 0:16:52.320 which is characterized by a total disregard for the feelings 0:16:52.360 --> 0:16:57.520 and rights of other people. And antisocial personality disorder, or ASPD, 0:16:58.080 --> 0:17:03.200 is highly prevalent among the criminal population. So the researchers 0:17:03.240 --> 0:17:07.480 found that ASPD had the highest likelihood of occurring when 0:17:07.600 --> 0:17:14.359 brain abnormalities were combined with a history of adverse environmental experiences. 0:17:14.600 --> 0:17:17.720 In other words, if you have certain problems with your brain, 0:17:17.800 --> 0:17:20.600 but you are raised in a good home, you might 0:17:20.640 --> 0:17:23.840 turn out fine. If your brain is fine and your 0:17:23.880 --> 0:17:26.919 home is terrible, you might still turn out fine. But 0:17:26.960 --> 0:17:30.040 if you have mild brain damage and end up in 0:17:30.119 --> 0:17:33.439 a bad home life, you're tossing the dice for a 0:17:33.680 --> 0:17:38.720 very unlucky synergy. All these examples demonstrate that it is 0:17:38.920 --> 0:17:44.400 neither biology alone nor your environment alone that determines the 0:17:44.440 --> 0:17:48.239 final product of a personality. When it comes to the 0:17:48.840 --> 0:17:54.320 nature versus nurture question, the answer almost always includes both. 0:17:55.200 --> 0:17:58.280 Now importantly, you don't choose your nature and you don't 0:17:58.400 --> 0:18:04.200 choose your nurture much less they're entangled interaction. You inherit 0:18:04.320 --> 0:18:07.880 a genetic blueprint, and you're born into a world over 0:18:07.920 --> 0:18:11.119 which you have no choice throughout your most formative years. 0:18:11.840 --> 0:18:14.240 This is the reason people come to the table with 0:18:14.400 --> 0:18:19.360 quite different ways of seeing the world, and dissimilar personalities 0:18:19.640 --> 0:18:24.560 and varied capacities for decision making. These are not choices. 0:18:24.840 --> 0:18:28.280 These are the hand of cards that you're dealt. The 0:18:28.359 --> 0:18:32.439 point of episode fifteen about neurolaw was to highlight the 0:18:32.600 --> 0:18:38.120 difficulty of assigning culpability under this circumstance of you choosing 0:18:38.240 --> 0:18:41.520 neither your genes or your environment. The point of this 0:18:41.640 --> 0:18:45.280 episode is to highlight the fact that the machinery that 0:18:45.400 --> 0:18:49.199 makes us who we are is not simple, and that 0:18:49.440 --> 0:18:54.240 science is not perched on the verge of understanding who 0:18:54.320 --> 0:18:57.960 you are and exactly how you came to be that way. 0:18:58.520 --> 0:19:01.760 So where we are is this weird place where we 0:19:01.880 --> 0:19:06.119 know without a doubt that minds and biology are connected, 0:19:06.560 --> 0:19:09.440 but we're not going to have any hope of understanding 0:19:09.520 --> 0:19:15.959 that connection with a purely reductionist approach. Reductionism is misleading 0:19:16.520 --> 0:19:21.080 for two reasons. First, as we've just seen, the unfathomable 0:19:21.280 --> 0:19:25.680 complexity of gene environment interactions puts us a long way 0:19:25.680 --> 0:19:30.880 from understanding how any individual person, with her lifetime of 0:19:30.960 --> 0:19:37.399 experiences and conversations and abuses and joys and foods she's eaten, 0:19:37.760 --> 0:19:43.200 and recreational drugs and prescribed medications and pesticides and educational 0:19:43.240 --> 0:19:46.040 experience and so on, we have no idea how she's 0:19:46.200 --> 0:19:50.280 going to develop as an individual. It is simply too complex, 0:19:50.640 --> 0:19:54.960 and presumably it is going to remain too complex. The 0:19:55.080 --> 0:19:59.440 second reason reductionism is misleading is that even while it's 0:19:59.560 --> 0:20:02.800 true that we are tied to our molecules and proteins 0:20:02.800 --> 0:20:07.359 and neurons, as strokes and hormones and drugs and microorganisms 0:20:07.440 --> 0:20:12.440 indisputably tell us, it doesn't logically follow that humans are 0:20:12.560 --> 0:20:16.919 best described only as pieces and parts. Like that, the 0:20:17.040 --> 0:20:20.360 extreme reductionist idea that we are no more than the 0:20:20.400 --> 0:20:23.919 cells of which we are composed is a non starter 0:20:24.320 --> 0:20:28.480 for anyone trying to understand human behavior. Just because a 0:20:28.560 --> 0:20:32.040 system is made of pieces and parts, and just because 0:20:32.119 --> 0:20:34.919 those pieces and parts are critical to the working of 0:20:34.960 --> 0:20:37.760 the system, that does not mean that the pieces and 0:20:37.840 --> 0:20:42.440 parts are the correct level of description. And I'll give 0:20:42.480 --> 0:20:46.080 a few examples of that in a moment. So, given 0:20:46.119 --> 0:20:49.520 these shortcomings of reductionism, why did it catch on in 0:20:49.560 --> 0:20:52.280 the first place. To understand this, we just need to 0:20:52.320 --> 0:20:57.240 look at the historical roots. Over recent centuries, thinking people 0:20:57.680 --> 0:21:01.520 watched the growth of deterministic science around them in the 0:21:01.560 --> 0:21:05.320 form of the equations of Galileo and Newton and others. 0:21:05.720 --> 0:21:10.080 These scientists pulled springs and rolled balls and dropped weights, 0:21:10.119 --> 0:21:13.400 and increasingly they were able to predict what the objects 0:21:13.440 --> 0:21:17.119 were going to do with simple equations. So by the 0:21:17.240 --> 0:21:22.240 nineteenth century, Pierre Simon Laplace had proposed that if one 0:21:22.280 --> 0:21:25.000 could know the position of every particle in the universe, 0:21:25.520 --> 0:21:29.280 then one could compute forward to know the entire future 0:21:29.760 --> 0:21:31.960 and crank the equations the other way to know everything 0:21:32.000 --> 0:21:36.320 in the past, this deterministic approach was massively successful. It 0:21:36.400 --> 0:21:40.320 predicted the flight of cannon balls and the movement of planets, 0:21:40.880 --> 0:21:44.920 and that success was at the heart of biological reductionism. 0:21:44.960 --> 0:21:48.920 The idea is that big things can be understood by 0:21:48.960 --> 0:21:53.840 discerning smaller and smaller pieces. In this viewpoint, the eras 0:21:53.880 --> 0:21:57.840 of understanding all point to the smaller levels humans can 0:21:57.840 --> 0:22:02.520 be understood in terms of biology, biology, the language of chemistry, chemistry, 0:22:02.520 --> 0:22:06.640 and the equations of atomic physics. In many ways, reductionism 0:22:06.680 --> 0:22:09.280 has been the engine of science for the past four 0:22:09.359 --> 0:22:13.320 hundred years, and in most fields it has done a 0:22:13.520 --> 0:22:18.800 great job. But reductionism isn't the right viewpoint for everything, 0:22:18.920 --> 0:22:22.520 and it certainly won't explain the relationship between the brain 0:22:22.760 --> 0:22:26.120 and the mind. This is because of a feature known 0:22:26.160 --> 0:22:30.760 as emergence. When you put together large numbers of pieces 0:22:30.800 --> 0:22:35.480 and parts, the whole can become something greater than the sum. 0:22:36.080 --> 0:22:39.120 None of the individual hunks of an airplane have the 0:22:39.160 --> 0:22:42.800 property of flight, but when they are attached together in 0:22:42.840 --> 0:22:47.160 the right way, the result takes to the air. A 0:22:47.359 --> 0:22:50.360 thin metal bar won't do you much good if you're 0:22:50.359 --> 0:22:53.919 trying to control a jaguar, but several of them in 0:22:54.080 --> 0:22:59.880 parallel standing up have the property of containment. This concept 0:22:59.880 --> 0:23:04.480 of emergent properties means that something new can be introduced 0:23:04.600 --> 0:23:08.520 that is not inherent in any of the parts. As 0:23:08.600 --> 0:23:12.600 another example, imagine that you were an urban highway planner 0:23:12.880 --> 0:23:16.399 and you needed to understand your city's traffic flow. You 0:23:16.440 --> 0:23:18.760 need to understand where the cars tend to bunch up, 0:23:18.800 --> 0:23:23.080 where people speed, where the most dangerous attempts at passing occur. 0:23:23.520 --> 0:23:26.440 It won't take you long to realize that an understanding 0:23:26.480 --> 0:23:30.960 of these issues will require some model of the psychology 0:23:31.160 --> 0:23:35.119 of the drivers. You would lose your job if you 0:23:35.240 --> 0:23:38.880 propose to study the length of the screws and the engine, 0:23:39.119 --> 0:23:42.800 or the combustion efficiency of the spark plugs. Those are 0:23:42.840 --> 0:23:47.760 the wrong levels of description for understanding traffic jams. This 0:23:47.840 --> 0:23:50.720 is not to say that the small pieces don't matter. 0:23:50.840 --> 0:23:55.080 They do matter. As we saw with brains, adding narcotics, 0:23:55.160 --> 0:23:59.760 or changing neurotransmitter levels or mutating genes, this can radically 0:23:59.800 --> 0:24:03.680 all alter the essence of a person. And similarly, if 0:24:03.720 --> 0:24:08.400 you modify screws and spark plugs, the engines work differently, 0:24:08.680 --> 0:24:10.919 and the cars might speed up or slow down, and 0:24:10.960 --> 0:24:14.560 other cars might crash. Into them, so the conclusion is clear. 0:24:15.200 --> 0:24:18.880 While traffic flow depends on the integrity of the parts, 0:24:19.480 --> 0:24:23.520 it is not in any meaningful way equivalent to the parts. 0:24:24.400 --> 0:24:26.480 Or think of it this way. If you want to 0:24:26.560 --> 0:24:30.720 know why the TV show Seinfeld is funny, you won't 0:24:30.720 --> 0:24:34.399 get very far by studying the transistors and capacitors in 0:24:34.440 --> 0:24:36.840 the back of your TV. You might be able to 0:24:37.359 --> 0:24:40.560 list all the electronic parts in great detail, and you'll 0:24:40.560 --> 0:24:43.239 probably learn a thing or two about electricity, but that 0:24:43.440 --> 0:24:49.200 won't get you any closer to understanding hilarity. Enjoying Seinfeld 0:24:49.840 --> 0:24:54.199 depends entirely on the integrity of the transistors, but the 0:24:54.359 --> 0:24:59.240 parts are not themselves funny. And it's exactly the same 0:24:59.320 --> 0:25:03.399 with neuros science. While minds depend on the integrity of 0:25:03.440 --> 0:25:08.719 the neurons, neurons are not themselves thinking and feeling, and 0:25:08.840 --> 0:25:13.840 this forces a reconsideration of how to build a scientific 0:25:13.880 --> 0:25:17.160 account of the brain. If we were to work out 0:25:17.160 --> 0:25:20.560 a complete physics of neurons and their chemicals, would that 0:25:20.720 --> 0:25:25.080 explain the mind? Probably not. The brain presumably does not 0:25:25.280 --> 0:25:28.240 break any of the laws of physics, but that doesn't 0:25:28.280 --> 0:25:33.760 mean that equations describing biochemical interactions will amount to the 0:25:33.800 --> 0:25:39.160 correct level of description, as the complexity theorist Stuart Kaufman 0:25:39.320 --> 0:25:43.159 puts it, quote, a couple in love walking along the 0:25:43.200 --> 0:25:46.479 banks of the sin are in fact a couple in 0:25:46.560 --> 0:25:50.720 love walking along the banks of the sin, not mere 0:25:51.040 --> 0:25:55.679 particles in motion unquote. So in the same way, a 0:25:55.840 --> 0:26:00.960 meaningful theory of human biology can't be reduced to chemistry 0:26:01.000 --> 0:26:04.760 and physics. Instead, it has to be understood in its 0:26:04.800 --> 0:26:10.040 own vocabulary of evolution and competition and reward and desire 0:26:10.160 --> 0:26:14.480 and reputation and greed and friendship and trust and hunger 0:26:14.560 --> 0:26:18.440 and so on, in the same way that traffic flow 0:26:18.800 --> 0:26:21.040 is not going to be understood in the vocabulary of 0:26:21.160 --> 0:26:25.040 screws and spark plugs, but instead in terms of speed 0:26:25.040 --> 0:26:28.760 limits and rush hours and road rage and people wanting 0:26:28.800 --> 0:26:31.320 to get home to their families as soon as possible 0:26:31.560 --> 0:26:35.679 when their workday is over. And there's another reason why 0:26:35.760 --> 0:26:39.320 the neural pieces and parts won't be sufficient for a 0:26:39.680 --> 0:26:44.159 full understanding of human experience, and that is your brain 0:26:44.840 --> 0:26:47.520 is not the only biological player in the game of 0:26:47.600 --> 0:26:51.320 determining who you are. The brain is tied in constant 0:26:51.359 --> 0:26:55.560 two way communication with the endocrine and immune systems, which 0:26:55.600 --> 0:26:58.639 can be thought of as the greater nervous system. The 0:26:58.920 --> 0:27:03.240 greater nervous system is in turn inseparable from the chemical 0:27:03.320 --> 0:27:08.000 environments that influence its development, including nutrition and lead paint 0:27:08.040 --> 0:27:11.520 and air pollutants and so on and even more. You 0:27:11.600 --> 0:27:15.840 are part of a complex social network that changes your 0:27:15.880 --> 0:27:20.040 biology with every interaction, and which your actions can change 0:27:20.040 --> 0:27:25.040 in return. This makes the borders interesting to contemplate. How 0:27:25.119 --> 0:27:27.800 should we define you? Where do you begin and where 0:27:27.800 --> 0:27:31.399 do you end? The only solution, I think is to 0:27:31.480 --> 0:27:37.159 consider the brain the densest concentration of unice. It's the 0:27:37.240 --> 0:27:40.720 peak of the mountain, but it's not the whole mountain. 0:27:41.760 --> 0:27:44.199 When we look at behavior and we talk about the 0:27:44.280 --> 0:27:47.840 role of the brain, this is actually a shorthand label 0:27:47.880 --> 0:27:51.960 that includes contributions from a much broader system, what we 0:27:52.040 --> 0:27:57.159 often call a psychobiosocial system. The brain is not so 0:27:57.280 --> 0:28:00.240 much the seat of the mind as the hu ubb 0:28:00.720 --> 0:28:20.160 of the mind. So let's summarize where we are following 0:28:20.200 --> 0:28:22.760 a one way street in the direction of the very 0:28:22.880 --> 0:28:26.880 small is the mistake that reductionism can make, and it's 0:28:27.160 --> 0:28:29.960 a trap that we want to avoid. Whenever you see 0:28:30.000 --> 0:28:33.960 a shorthand statement such as you are your brain which 0:28:34.000 --> 0:28:37.400 I say sometimes don't take that to mean that neuroscience 0:28:37.440 --> 0:28:42.520 will understand minds only as massive constellations of atoms or 0:28:42.800 --> 0:28:46.640 vast jungles of neurons. Instead, the future of understanding the 0:28:46.720 --> 0:28:51.160 mind lies in deciphering the patterns of activity that live 0:28:51.240 --> 0:28:54.200 on top of the wetwear, and these patterns are directed 0:28:54.320 --> 0:28:58.600 both by the internal workings and by interactions from the 0:28:58.680 --> 0:29:03.960 surrounding world. So laboratories all over the world are working 0:29:04.040 --> 0:29:08.160