1 00:00:05,400 --> 00:00:09,440 Speaker 1: Although every cell in your body changes such that you 2 00:00:09,520 --> 00:00:14,440 Speaker 1: are never again the same person physically, and your neural 3 00:00:14,480 --> 00:00:17,680 Speaker 1: networks change every hour of your life as you absorb 4 00:00:17,760 --> 00:00:23,240 Speaker 1: new experiences. Why do you have an illusion of consistency, 5 00:00:23,360 --> 00:00:26,880 Speaker 1: as though you're the same person you were a week 6 00:00:26,880 --> 00:00:29,800 Speaker 1: ago or a year ago. What does this have to 7 00:00:29,840 --> 00:00:34,640 Speaker 1: do with the mythical watercraft of the Greek demigod Theseus? 8 00:00:35,360 --> 00:00:39,360 Speaker 1: What is the end of history illusion? And why do 9 00:00:39,440 --> 00:00:43,000 Speaker 1: you go through so much trouble to make things comfortable 10 00:00:43,159 --> 00:00:46,879 Speaker 1: for your future self even though you don't know that 11 00:00:47,000 --> 00:00:50,159 Speaker 1: person and you can be guaranteed that that person is 12 00:00:50,200 --> 00:00:52,640 Speaker 1: not going to feel the same way you do now. 13 00:00:53,440 --> 00:00:57,400 Speaker 1: And if there were an afterlife, what age would your 14 00:00:57,480 --> 00:01:04,920 Speaker 1: deity dial you to for living out eternity? Welcome to 15 00:01:04,959 --> 00:01:08,360 Speaker 1: Inner Cosmos with me David Eagleman. I'm a neuroscientist and 16 00:01:08,400 --> 00:01:12,160 Speaker 1: an author at Stanford and in these episodes we dive 17 00:01:12,240 --> 00:01:15,600 Speaker 1: deeply into our three pound universe to uncover some of 18 00:01:15,640 --> 00:01:30,080 Speaker 1: the most surprising aspects of our lives. Today, we're going 19 00:01:30,120 --> 00:01:33,440 Speaker 1: to talk about the notion of having a self and 20 00:01:33,600 --> 00:01:36,520 Speaker 1: what that has to do with our memory. And this 21 00:01:36,600 --> 00:01:38,280 Speaker 1: is a big topic, so we're going to do this 22 00:01:38,400 --> 00:01:41,920 Speaker 1: in two parts. Today, we're going to talk about how 23 00:01:42,000 --> 00:01:45,680 Speaker 1: and why we think of ourselves as lasting through time 24 00:01:46,120 --> 00:01:48,560 Speaker 1: and what that has to do with our memories. And 25 00:01:48,800 --> 00:01:51,560 Speaker 1: in next week's episode, part two, I'm going to talk 26 00:01:51,600 --> 00:01:55,320 Speaker 1: with my colleague, neuroscientist Michael Levin, one of the most 27 00:01:55,520 --> 00:01:58,600 Speaker 1: energized and original thinkers in the field, and I'm going 28 00:01:58,640 --> 00:02:01,040 Speaker 1: to talk with him about the way which memories can 29 00:02:01,120 --> 00:02:04,440 Speaker 1: be thought of like little creatures of their own that 30 00:02:04,640 --> 00:02:08,440 Speaker 1: carry messages in a bottle from one version of you 31 00:02:08,720 --> 00:02:13,280 Speaker 1: to the next. So for today, let's start in ancient Greece, 32 00:02:13,440 --> 00:02:17,480 Speaker 1: where the historian Bluetarch wrote about a tough puzzle that 33 00:02:17,520 --> 00:02:20,960 Speaker 1: had been floating around in the Greek philosopher circles, and 34 00:02:21,000 --> 00:02:24,639 Speaker 1: they were all arguing about it. The puzzle was this, 35 00:02:25,320 --> 00:02:30,240 Speaker 1: imagine the ship of Theseus. Theseus was the hero in 36 00:02:30,280 --> 00:02:33,160 Speaker 1: Greek mythology who slayed the minotaur. The idea is that 37 00:02:33,360 --> 00:02:37,520 Speaker 1: Theseus and his crew of Athenians sail back from Crete 38 00:02:37,560 --> 00:02:41,760 Speaker 1: and dock his wonderful ship. But then the ship sits 39 00:02:41,800 --> 00:02:44,760 Speaker 1: in harbor for a long time and one of the 40 00:02:44,800 --> 00:02:48,919 Speaker 1: planks starts to rot, so it gets replaced with new 41 00:02:49,000 --> 00:02:52,359 Speaker 1: and stronger timber, and then that happens with another plank 42 00:02:52,440 --> 00:02:56,240 Speaker 1: on the ship, and another, and eventually, with enough time, 43 00:02:56,720 --> 00:03:01,280 Speaker 1: the entire ship gets replaced, meaning that a single plank 44 00:03:01,680 --> 00:03:04,079 Speaker 1: is the same as what it was when the ship 45 00:03:04,400 --> 00:03:08,000 Speaker 1: first docked. And the question is is it the same 46 00:03:08,400 --> 00:03:11,800 Speaker 1: ship of Theseus or is it not his ship anymore? 47 00:03:11,840 --> 00:03:16,560 Speaker 1: Because every single part has been replaced. Plutarch suggested that 48 00:03:16,800 --> 00:03:19,720 Speaker 1: half the philosophers in Greece argue the ship is still 49 00:03:19,760 --> 00:03:23,880 Speaker 1: the same ship because it retains its identity despite the 50 00:03:23,960 --> 00:03:27,160 Speaker 1: changes to its parts, and the other half of philosophers, 51 00:03:27,200 --> 00:03:30,320 Speaker 1: he suggested, argued that the ship is not the same 52 00:03:30,360 --> 00:03:33,360 Speaker 1: ship because no part of it is the same. So 53 00:03:33,960 --> 00:03:37,680 Speaker 1: for thousands of years, the Ship of Theseus has been 54 00:03:37,720 --> 00:03:42,640 Speaker 1: a thought experiment that surfaces these tough questions about identity 55 00:03:42,760 --> 00:03:46,160 Speaker 1: and change. By the way, there are lots of variants 56 00:03:46,200 --> 00:03:49,200 Speaker 1: on this. My father had an axe in the garage, 57 00:03:49,440 --> 00:03:51,160 Speaker 1: and he would always hold it up and tell me 58 00:03:51,760 --> 00:03:56,040 Speaker 1: this was actually George Washington's axe. Oh, but the handle 59 00:03:56,080 --> 00:03:58,920 Speaker 1: has been replaced twelve times and the axe head has 60 00:03:58,960 --> 00:04:02,600 Speaker 1: been replaced for times. It was obviously a joke, but 61 00:04:02,640 --> 00:04:05,440 Speaker 1: it got me thinking from a young age about the 62 00:04:05,520 --> 00:04:09,760 Speaker 1: nature of identity in the face of change. Does something 63 00:04:09,840 --> 00:04:14,400 Speaker 1: retain its identity if all departs change? Now, why would 64 00:04:14,440 --> 00:04:18,279 Speaker 1: a neuroscience podcast care about the Ship of Theseus or 65 00:04:18,480 --> 00:04:23,599 Speaker 1: George Washington's acts. It's because that kind of wholesale replacement 66 00:04:23,760 --> 00:04:28,279 Speaker 1: is precisely what's happening to your brain and your entire body. 67 00:04:28,960 --> 00:04:32,039 Speaker 1: A big part of the mystery of selfhood has to 68 00:04:32,080 --> 00:04:34,600 Speaker 1: do with the fact that all the pieces and parts 69 00:04:34,640 --> 00:04:40,360 Speaker 1: that make up you are constantly turning over. Your body 70 00:04:40,400 --> 00:04:43,880 Speaker 1: is built out of thirty trillion cells, and this is 71 00:04:43,960 --> 00:04:49,080 Speaker 1: just cellular stuff. Every bit of the cells has a lifetime. 72 00:04:49,560 --> 00:04:52,599 Speaker 1: Most of the cells die or subdivide at some point. 73 00:04:52,680 --> 00:04:55,440 Speaker 1: But even those cells that stick around your whole life 74 00:04:55,480 --> 00:04:59,280 Speaker 1: and don't divide, like your neurons, they're totally different every 75 00:04:59,320 --> 00:05:03,120 Speaker 1: few years. Why because brain cells aren't made out of 76 00:05:03,120 --> 00:05:06,960 Speaker 1: something stable like metal or cement. Instead, they're made out 77 00:05:07,000 --> 00:05:10,960 Speaker 1: of the basic proteins and lipids and other molecules that 78 00:05:11,080 --> 00:05:13,599 Speaker 1: make up any cell in the body, and those things 79 00:05:13,680 --> 00:05:18,360 Speaker 1: aren't particularly stable. So every single neuron and every cell 80 00:05:18,360 --> 00:05:22,320 Speaker 1: in your body is like the Ship of Theseus. Every 81 00:05:22,360 --> 00:05:25,600 Speaker 1: part of it is getting rebuilt all the time, one 82 00:05:25,720 --> 00:05:28,640 Speaker 1: planket a time, or in this case one molecule at 83 00:05:28,680 --> 00:05:32,359 Speaker 1: a time. The pieces and parts of the cell have 84 00:05:32,520 --> 00:05:36,200 Speaker 1: no meaningful stability, and so a big part of all 85 00:05:36,279 --> 00:05:41,200 Speaker 1: that cellular machinery is simply building and rebuilding and rebuilding, 86 00:05:41,760 --> 00:05:45,680 Speaker 1: and in this way everything gets replaced. So who you 87 00:05:45,839 --> 00:05:49,800 Speaker 1: are physically changes all the time, and the question is 88 00:05:50,240 --> 00:05:55,520 Speaker 1: how does your self stay intact over this changing substrate. 89 00:05:56,279 --> 00:06:00,720 Speaker 1: The answer is it's not clear that it does. But 90 00:06:00,880 --> 00:06:07,520 Speaker 1: cognitively you have this illusion of stability. You are one being. 91 00:06:07,680 --> 00:06:10,560 Speaker 1: You've spent your whole life with a fixed history, as in, 92 00:06:11,000 --> 00:06:14,680 Speaker 1: I grew up here, here's my name, this was my hometown, 93 00:06:14,839 --> 00:06:18,000 Speaker 1: these are my parents. This is how my trajectory in 94 00:06:18,040 --> 00:06:20,760 Speaker 1: life has unfolded, leading me from here to there to there. 95 00:06:20,800 --> 00:06:23,039 Speaker 1: And so we tend to hold the impression that our 96 00:06:23,440 --> 00:06:27,800 Speaker 1: identities are something very stable, but in fact who you 97 00:06:28,120 --> 00:06:31,680 Speaker 1: are drifts in this light. It's always struck me as 98 00:06:31,720 --> 00:06:34,520 Speaker 1: funny to think about the notion of an afterlife, because 99 00:06:34,880 --> 00:06:38,440 Speaker 1: what age would you be Depending on when you get there, 100 00:06:38,480 --> 00:06:41,240 Speaker 1: you might be a very different person than you were 101 00:06:41,360 --> 00:06:44,320 Speaker 1: even five years before that. And so all this inspired 102 00:06:44,360 --> 00:06:47,200 Speaker 1: me to write a short story that's published in my 103 00:06:47,240 --> 00:06:50,560 Speaker 1: book Some sum and I'm going to read that story 104 00:06:50,839 --> 00:06:54,640 Speaker 1: to illustrate the questions of this episode. The story is 105 00:06:54,680 --> 00:06:58,680 Speaker 1: called Prism. God resolved at the outset that he wanted 106 00:06:58,800 --> 00:07:02,680 Speaker 1: every human to partippaid in the afterlife, but the plans 107 00:07:03,040 --> 00:07:06,919 Speaker 1: weren't thought out to completion, and immediately he began to 108 00:07:07,000 --> 00:07:11,720 Speaker 1: run up against some confusion about age. How old should 109 00:07:11,760 --> 00:07:15,760 Speaker 1: each person be in the afterlife. Should this grandmother exist 110 00:07:15,800 --> 00:07:19,040 Speaker 1: here at her age of death, or should she be 111 00:07:19,080 --> 00:07:22,800 Speaker 1: allowed to live as a young woman, recognizable to her 112 00:07:22,840 --> 00:07:26,600 Speaker 1: first lover but not to her granddaughter. He decided it 113 00:07:26,680 --> 00:07:29,920 Speaker 1: was unfair to keep people the age they were at 114 00:07:29,920 --> 00:07:32,920 Speaker 1: the end of their lives, when much of their beauty 115 00:07:33,000 --> 00:07:36,840 Speaker 1: and alacrity had been worn down. Allowing everyone to live 116 00:07:36,880 --> 00:07:41,320 Speaker 1: as a young adult proved an unviable solution, because the 117 00:07:41,360 --> 00:07:46,560 Speaker 1: afterlife quickly degenerated into unbounded sexual pursuits, and at middle 118 00:07:46,560 --> 00:07:50,119 Speaker 1: ages they talked only about their children and mortgages, making 119 00:07:50,160 --> 00:07:55,080 Speaker 1: conversations in the afterlife. Tedious God finally landed on an 120 00:07:55,280 --> 00:08:00,200 Speaker 1: ingenious solution while watching light diffract through a prism. So 121 00:08:00,240 --> 00:08:03,600 Speaker 1: when you arrive here, you are split into your multiple 122 00:08:03,680 --> 00:08:08,440 Speaker 1: selves at all possible ages. The you that existed as 123 00:08:08,480 --> 00:08:13,520 Speaker 1: a single identity is now all ages at once. These 124 00:08:13,680 --> 00:08:17,520 Speaker 1: pieces of you no longer get old, but remain ageless 125 00:08:17,600 --> 00:08:23,000 Speaker 1: into perpetuity. The ewes have transcended time. This takes them 126 00:08:23,000 --> 00:08:26,400 Speaker 1: getting used to The different beams of you might run 127 00:08:26,400 --> 00:08:29,240 Speaker 1: into each other at the grocery store, like separate people 128 00:08:29,280 --> 00:08:32,480 Speaker 1: do in earth life. Your seventy six year old self 129 00:08:32,840 --> 00:08:36,560 Speaker 1: may revisit his favorite creek and run into your eleven 130 00:08:36,640 --> 00:08:39,559 Speaker 1: year old self. Your twenty eight year old self may 131 00:08:39,559 --> 00:08:42,120 Speaker 1: break up with a lover and a diner and notice 132 00:08:42,160 --> 00:08:46,160 Speaker 1: your thirty five year old self visiting that spot, lingering 133 00:08:46,320 --> 00:08:50,720 Speaker 1: on the air of regret hanging over the empty seat. Typically, 134 00:08:51,120 --> 00:08:53,959 Speaker 1: the different youws are happy to see each other because 135 00:08:54,200 --> 00:08:57,320 Speaker 1: they possess the same name in a shared history. But 136 00:08:57,600 --> 00:09:00,480 Speaker 1: the ewes are more critical of yourselves than they are 137 00:09:00,480 --> 00:09:05,160 Speaker 1: of others, and so each you quickly identifies habits that 138 00:09:05,240 --> 00:09:08,559 Speaker 1: get under your skin. It's a fact of the afterlife. 139 00:09:09,040 --> 00:09:13,319 Speaker 1: Don't be surprised to discover that after decomposition into your 140 00:09:13,440 --> 00:09:18,960 Speaker 1: different ages, the different us tend to drift apart. You 141 00:09:19,080 --> 00:09:22,600 Speaker 1: discover that the you of eight years old has less 142 00:09:22,640 --> 00:09:25,320 Speaker 1: than common than expected with the U of thirty two 143 00:09:25,760 --> 00:09:28,840 Speaker 1: and the U of sixty four. The eighteen year old 144 00:09:28,880 --> 00:09:32,200 Speaker 1: you finds more in common with other eighteen year olds 145 00:09:32,480 --> 00:09:35,760 Speaker 1: than with your seventy three year old you. The seventy 146 00:09:35,800 --> 00:09:38,480 Speaker 1: three year old you doesn't mind a bit seeking out 147 00:09:38,520 --> 00:09:44,079 Speaker 1: meaningful conversations with others of the same generation. Beyond the name, 148 00:09:44,720 --> 00:09:48,920 Speaker 1: the us have little else in common, but don't lose hope. 149 00:09:49,320 --> 00:09:54,400 Speaker 1: The shared resume of life, parents, birthplace, hometown, school, years, 150 00:09:54,480 --> 00:09:58,839 Speaker 1: first kiss has a magnetic nostalgic pull. So once in 151 00:09:58,920 --> 00:10:02,800 Speaker 1: a while, the different yous organize a gathering like a 152 00:10:02,840 --> 00:10:07,800 Speaker 1: family reunion, bringing together all your ages into a single room. 153 00:10:08,120 --> 00:10:11,520 Speaker 1: At these reunions, the middle aged will delightedly pinch the 154 00:10:11,640 --> 00:10:15,160 Speaker 1: cheeks of the young, and the teenagers will politely listen 155 00:10:15,240 --> 00:10:18,960 Speaker 1: to the stories and advice of the elderly. These reunions 156 00:10:19,320 --> 00:10:23,960 Speaker 1: reveal a group of individuals touchingly searching for a common theme. 157 00:10:24,600 --> 00:10:27,960 Speaker 1: They appeal to your name as a unifying structure, but 158 00:10:28,040 --> 00:10:31,480 Speaker 1: they come to realize that the name that existed on earth, 159 00:10:31,960 --> 00:10:36,400 Speaker 1: the you that moved serially through these different identities, was 160 00:10:36,480 --> 00:10:40,400 Speaker 1: like a bundle of sticks from different trees. They come 161 00:10:40,440 --> 00:10:45,840 Speaker 1: to understand with awe the complexity of the compound identity 162 00:10:45,920 --> 00:10:49,360 Speaker 1: that existed on the earth. They conclude with a shudder, 163 00:10:49,840 --> 00:10:55,559 Speaker 1: that the earthly you is utterly lost, unpreserved in the afterlife. 164 00:10:55,600 --> 00:11:00,600 Speaker 1: You were all these ages, they concede, and you were none. 165 00:11:15,280 --> 00:11:18,040 Speaker 1: So we're changing all the time. But why is it 166 00:11:18,440 --> 00:11:21,960 Speaker 1: hard to keep track of these changes. Obviously it's because 167 00:11:22,280 --> 00:11:26,479 Speaker 1: everything in our lives and our biology changes so slowly. 168 00:11:27,000 --> 00:11:30,160 Speaker 1: It's like the hour hand of a clock. You can 169 00:11:30,160 --> 00:11:32,720 Speaker 1: see that it's moved, but you can't see it move. 170 00:11:33,440 --> 00:11:36,440 Speaker 1: In general, we can see change most readily in the 171 00:11:36,480 --> 00:11:39,839 Speaker 1: growth of our children. You look back at photographs from 172 00:11:39,880 --> 00:11:42,240 Speaker 1: a year ago on your phone and you can't believe 173 00:11:42,280 --> 00:11:44,800 Speaker 1: how much things have changed. But it's hard to keep 174 00:11:44,880 --> 00:11:48,800 Speaker 1: track of the changes in yourself. A friend of my 175 00:11:48,920 --> 00:11:52,080 Speaker 1: parents went to his high school reunion, which was taking 176 00:11:52,120 --> 00:11:54,400 Speaker 1: place at a hotel, and he went around looking at 177 00:11:54,440 --> 00:11:57,440 Speaker 1: the different conference rooms to figure out which one was 178 00:11:57,480 --> 00:12:00,160 Speaker 1: the correct class, because they were divided up by decades, 179 00:12:00,559 --> 00:12:02,280 Speaker 1: And he thought he found the right room, but he 180 00:12:02,320 --> 00:12:05,640 Speaker 1: popped his head in and he realized that's completely not 181 00:12:05,720 --> 00:12:07,880 Speaker 1: the right room. All of those are very old people. 182 00:12:08,200 --> 00:12:10,360 Speaker 1: And then he stepped back and looked at the sign 183 00:12:10,760 --> 00:12:13,880 Speaker 1: and realized that indeed this was the correct room, and 184 00:12:14,000 --> 00:12:17,800 Speaker 1: he too must presumably look that old to others, even 185 00:12:17,880 --> 00:12:21,119 Speaker 1: if he still thought of himself as young on the inside. 186 00:12:21,840 --> 00:12:24,120 Speaker 1: So it's hard to keep track of our own changes 187 00:12:24,120 --> 00:12:29,640 Speaker 1: because they happen slowly. But maybe the thing that binds 188 00:12:29,679 --> 00:12:34,760 Speaker 1: your self together across the ever changing physical substrate is 189 00:12:34,800 --> 00:12:38,560 Speaker 1: the one thing you have that remains constant, your memory. 190 00:12:39,240 --> 00:12:43,040 Speaker 1: Memory ties all these versions of you together. Memory serves 191 00:12:43,080 --> 00:12:47,560 Speaker 1: as the thread that weaves through all these transformations, anchoring 192 00:12:48,120 --> 00:12:50,599 Speaker 1: a sense of self. So that sounds very nice, but 193 00:12:50,640 --> 00:12:53,880 Speaker 1: there's a fundamental problem with this, which is that memory 194 00:12:53,960 --> 00:12:58,440 Speaker 1: itself is not stable. It drifts, and I've talked about 195 00:12:58,440 --> 00:13:03,760 Speaker 1: this in several episodes. Memory is not a faithful, unchanging 196 00:13:03,840 --> 00:13:07,920 Speaker 1: record of the past. It's instead a fragile brain state, 197 00:13:08,000 --> 00:13:11,760 Speaker 1: and it needs to be reactivated and reconstructed each time 198 00:13:11,880 --> 00:13:17,120 Speaker 1: you recall it. And in this process, memories morph, So 199 00:13:17,120 --> 00:13:19,600 Speaker 1: we can't really think of them as an archive. They're 200 00:13:19,600 --> 00:13:24,560 Speaker 1: more of a story which we continually rewrite. And that 201 00:13:24,600 --> 00:13:27,320 Speaker 1: would be fine to keep rewriting a story, except that 202 00:13:27,320 --> 00:13:30,440 Speaker 1: we assume at all times that our memories form the 203 00:13:30,600 --> 00:13:34,120 Speaker 1: core of a stable identity. So let me give an 204 00:13:34,160 --> 00:13:37,720 Speaker 1: example of how memories change Imagine that you and two 205 00:13:37,800 --> 00:13:41,040 Speaker 1: friends were at some rooftop party and you were best 206 00:13:41,040 --> 00:13:43,760 Speaker 1: friends since college, and the night was full of jokes 207 00:13:43,760 --> 00:13:47,320 Speaker 1: and old stories, and you remember feeling grateful for this 208 00:13:47,440 --> 00:13:49,959 Speaker 1: bond that you shared, and you can still picture the 209 00:13:50,000 --> 00:13:53,360 Speaker 1: three of you by the fireplace, vowing to never let 210 00:13:53,400 --> 00:13:57,439 Speaker 1: life pull you apart. But now, a year later, everything 211 00:13:57,440 --> 00:14:00,720 Speaker 1: has changed. Those two guys are now enemies. It all 212 00:14:00,800 --> 00:14:02,920 Speaker 1: fell apart because one of them had an affair with 213 00:14:02,960 --> 00:14:05,920 Speaker 1: the other's girlfriend. So now when you think back on 214 00:14:05,960 --> 00:14:09,360 Speaker 1: that rooftop party, you wonder was there something in the 215 00:14:09,400 --> 00:14:13,880 Speaker 1: way he and the other guy's girlfriend exchanged glances across 216 00:14:13,920 --> 00:14:17,240 Speaker 1: the room? You now think you sort of remember there 217 00:14:17,280 --> 00:14:20,960 Speaker 1: were little stolen looks, there was some subtle tension in 218 00:14:21,000 --> 00:14:24,200 Speaker 1: the air. Did your other friends sense that something was funny? 219 00:14:24,400 --> 00:14:28,000 Speaker 1: Even then, the memory that once felt warm and comforting 220 00:14:28,040 --> 00:14:31,080 Speaker 1: now feels different, like a scene in a movie that 221 00:14:31,120 --> 00:14:34,520 Speaker 1: you're watching for the second time but noticing new things now. 222 00:14:34,640 --> 00:14:38,040 Speaker 1: The past hasn't changed, but your present knowledge of what 223 00:14:38,200 --> 00:14:42,640 Speaker 1: came after that party colors the memory and reshapes it, 224 00:14:42,680 --> 00:14:44,600 Speaker 1: and it makes you question what was really there and 225 00:14:44,640 --> 00:14:49,760 Speaker 1: what you've unconsciously added. Memory is slippery, like that, the 226 00:14:49,760 --> 00:14:53,440 Speaker 1: more you revisit it, the more it shifts and blurs, 227 00:14:53,960 --> 00:14:56,960 Speaker 1: which reminds me of a great quotation from Sigmund Freud 228 00:14:57,040 --> 00:14:59,600 Speaker 1: on this topic. In eighteen ninety six, he wrote a 229 00:14:59,640 --> 00:15:03,320 Speaker 1: letter to to a colleague about quote, the material present 230 00:15:03,480 --> 00:15:08,160 Speaker 1: in the form of memory traces being subjected from time 231 00:15:08,200 --> 00:15:13,120 Speaker 1: to time to a rearrangement in accordance with fresh circumstances, 232 00:15:13,160 --> 00:15:17,600 Speaker 1: to a retranscription. And there's another quotation that I cite 233 00:15:17,720 --> 00:15:21,080 Speaker 1: often from a writer named John Dufresny, who once wrote 234 00:15:21,120 --> 00:15:25,200 Speaker 1: that quote, Memory is a myth making machine. What we 235 00:15:25,280 --> 00:15:29,440 Speaker 1: do is keep revising our past to keep it consistent 236 00:15:29,880 --> 00:15:33,120 Speaker 1: with who we think we are. So here's where we 237 00:15:33,200 --> 00:15:36,320 Speaker 1: are so far. Our biology is always changing, and so 238 00:15:36,440 --> 00:15:39,600 Speaker 1: the thing that crosses time is our memory. But even 239 00:15:39,640 --> 00:15:43,600 Speaker 1: that changes all the time, drifting or warping or disintegrating altogether. 240 00:15:44,040 --> 00:15:47,560 Speaker 1: And as a result, who you are is always on 241 00:15:47,640 --> 00:15:50,800 Speaker 1: the move. Now, I've been speaking as though we're not 242 00:15:51,080 --> 00:15:54,320 Speaker 1: always aware of so much change happening over time, But 243 00:15:54,360 --> 00:15:56,080 Speaker 1: of course we can come to be aware of this 244 00:15:56,160 --> 00:15:59,280 Speaker 1: in some circumstances. For example, when you look back at 245 00:15:59,320 --> 00:16:02,320 Speaker 1: a diary entry that you wrote some years ago, it's 246 00:16:02,360 --> 00:16:06,240 Speaker 1: often surprising how much you've changed, how much the person 247 00:16:06,280 --> 00:16:09,640 Speaker 1: who held that pen is a bit different than who 248 00:16:09,720 --> 00:16:13,520 Speaker 1: you are now. So we do confront this sometimes. But 249 00:16:13,640 --> 00:16:17,280 Speaker 1: what's weird is despite the massive changes that happen in 250 00:16:17,320 --> 00:16:20,880 Speaker 1: our past, we always think that there will be little 251 00:16:21,000 --> 00:16:24,760 Speaker 1: change in the future. We've changed a lot up until now, 252 00:16:24,800 --> 00:16:27,720 Speaker 1: but now we've settled into place and there won't be 253 00:16:27,840 --> 00:16:31,560 Speaker 1: much change from here. And this is a cognitive illusion 254 00:16:31,720 --> 00:16:35,640 Speaker 1: known as the end of history illusion. In other words, 255 00:16:35,840 --> 00:16:39,160 Speaker 1: we can recognize significant changes in ourselves when we think 256 00:16:39,200 --> 00:16:42,440 Speaker 1: about our past, but we underestimate how much we're going 257 00:16:42,480 --> 00:16:46,120 Speaker 1: to change in the future. We acknowledge that we've grown 258 00:16:46,200 --> 00:16:50,040 Speaker 1: or evolved, but we incorrectly assume that who we are 259 00:16:50,160 --> 00:16:54,200 Speaker 1: right now is pretty close to our final or mature 260 00:16:54,400 --> 00:16:58,960 Speaker 1: version of ourselves. This end of history illusion was first 261 00:16:58,960 --> 00:17:02,160 Speaker 1: studied by psychology just like Daniel Gilbert and his colleagues, 262 00:17:02,400 --> 00:17:05,800 Speaker 1: and they surveyed people on their values and their preferences, 263 00:17:05,840 --> 00:17:09,159 Speaker 1: their personality traits, their life goals, and across the board. 264 00:17:09,200 --> 00:17:13,840 Speaker 1: They found that people consistently believe that they've undergone more 265 00:17:13,960 --> 00:17:15,919 Speaker 1: change in the past than they will in the future. 266 00:17:16,240 --> 00:17:20,359 Speaker 1: But of course it's an illusion because change is a 267 00:17:20,440 --> 00:17:24,280 Speaker 1: continuous process. In other words, if I ask you now 268 00:17:24,600 --> 00:17:28,000 Speaker 1: if you've essentially finished changing in life, if you're likes 269 00:17:28,000 --> 00:17:30,520 Speaker 1: and personality have settled, you'll say yeah. But if I 270 00:17:30,640 --> 00:17:33,719 Speaker 1: track you down and ask you again in five years, 271 00:17:33,800 --> 00:17:37,600 Speaker 1: you'll say, actually, the past five years did hold a 272 00:17:37,640 --> 00:17:41,080 Speaker 1: lot of change for me, but now I've finally arrived 273 00:17:41,080 --> 00:17:43,560 Speaker 1: at my stable self. And it's the same story if 274 00:17:43,560 --> 00:17:46,119 Speaker 1: I survey you five years after that. And this is 275 00:17:46,200 --> 00:17:50,440 Speaker 1: problematic because, for example, we're always trying to predict our 276 00:17:50,480 --> 00:17:54,360 Speaker 1: future emotions. You think, oh, if I get that job promotion, 277 00:17:54,680 --> 00:17:57,800 Speaker 1: or if I'm in this relationship, or if I have kids, 278 00:17:57,840 --> 00:18:00,520 Speaker 1: or if I don't have kids, this will make me happy. 279 00:18:00,600 --> 00:18:02,520 Speaker 1: Or if I lose this job and I have to 280 00:18:02,560 --> 00:18:04,440 Speaker 1: find a new one, that's going to make me miserable. 281 00:18:04,560 --> 00:18:09,320 Speaker 1: This is what psychologists call affective forecasting, where we project 282 00:18:09,400 --> 00:18:11,960 Speaker 1: how we think we're going to feel, but it's based 283 00:18:11,960 --> 00:18:15,280 Speaker 1: on your current limited knowledge about the world, and that 284 00:18:15,359 --> 00:18:18,119 Speaker 1: might change. So why do we have an end of 285 00:18:18,200 --> 00:18:21,679 Speaker 1: history illusion. Well, presumably it's because it's easier for us 286 00:18:21,720 --> 00:18:25,040 Speaker 1: to see the past changes because we have memories and 287 00:18:25,080 --> 00:18:30,280 Speaker 1: experiences to draw from, but future changes are hidden in 288 00:18:30,320 --> 00:18:32,800 Speaker 1: the mists of the future. We don't know what they are, 289 00:18:33,280 --> 00:18:36,080 Speaker 1: so let me give you some concrete examples of this. 290 00:18:36,480 --> 00:18:40,160 Speaker 1: Think about the way we have our career goals. As 291 00:18:40,200 --> 00:18:42,399 Speaker 1: a thirty year old, you might look back and realize 292 00:18:42,440 --> 00:18:46,760 Speaker 1: your career aspirations have changed, maybe significantly, from the time 293 00:18:46,800 --> 00:18:49,480 Speaker 1: you were twenty, but you might assume that your current 294 00:18:49,560 --> 00:18:52,720 Speaker 1: career goals are unlikely to change much in the next 295 00:18:52,720 --> 00:18:55,440 Speaker 1: ten years, even though lots of people shift career paths 296 00:18:55,520 --> 00:18:58,800 Speaker 1: or professional interests throughout life. Or think about your music 297 00:18:58,960 --> 00:19:02,600 Speaker 1: preferences you are older. You may recognize that your taste 298 00:19:02,600 --> 00:19:06,080 Speaker 1: in music has evolved since your teenage years. Maybe you 299 00:19:06,119 --> 00:19:10,480 Speaker 1: went from popper rock to maybe jazz or classical. But 300 00:19:10,720 --> 00:19:13,480 Speaker 1: despite that, you're likely to believe that your current musical 301 00:19:13,520 --> 00:19:16,359 Speaker 1: preferences are going to remain stable for the rest of 302 00:19:16,400 --> 00:19:18,679 Speaker 1: your life, even though your musical tastes are going to 303 00:19:18,800 --> 00:19:23,280 Speaker 1: keep evolving with exposure to new genres and bands and 304 00:19:23,400 --> 00:19:27,000 Speaker 1: instruments that don't even exist yet. We're thinking about friendships. 305 00:19:27,520 --> 00:19:30,560 Speaker 1: In your early twenties, you might reflect on how your 306 00:19:30,600 --> 00:19:34,160 Speaker 1: circle of friends has changed from high school to college. 307 00:19:34,280 --> 00:19:36,880 Speaker 1: There's a big shift in relationships there, but you might 308 00:19:36,920 --> 00:19:40,280 Speaker 1: simultaneously feel certain that the college friends you have now 309 00:19:40,800 --> 00:19:43,800 Speaker 1: are going to be your closest companions for life. That's 310 00:19:43,840 --> 00:19:49,520 Speaker 1: a totally understandable position, but it underestimates how friendships shift 311 00:19:49,640 --> 00:19:52,600 Speaker 1: as you enter different life stages, like when you start 312 00:19:52,640 --> 00:19:54,919 Speaker 1: a family or you move to a new city. The 313 00:19:55,000 --> 00:19:58,600 Speaker 1: same reasoning applies to everything, So take hobbies and interest 314 00:19:58,680 --> 00:20:01,800 Speaker 1: When you're in your fish, you notice that you've taken 315 00:20:01,920 --> 00:20:04,720 Speaker 1: up new hobbies and given up old ones over the years, 316 00:20:04,720 --> 00:20:08,040 Speaker 1: but you'll generally believe that your current interests will remain 317 00:20:08,160 --> 00:20:11,800 Speaker 1: consistent for the coming decades, when in fact, new hobbies 318 00:20:11,800 --> 00:20:14,760 Speaker 1: and interests will still emerge. You just can't see that 319 00:20:14,880 --> 00:20:18,880 Speaker 1: because they're ensconced in the dark forest of the future. 320 00:20:19,440 --> 00:20:22,680 Speaker 1: Possibly there's some new technology that you're going to be 321 00:20:22,720 --> 00:20:26,600 Speaker 1: obsessed with that hasn't even been invented or named yet. Okay, 322 00:20:26,640 --> 00:20:29,280 Speaker 1: And the one that's really hard for us to admit 323 00:20:29,359 --> 00:20:35,120 Speaker 1: to is future changes in our political values and social beliefs, 324 00:20:35,160 --> 00:20:38,840 Speaker 1: and possibly religious beliefs. When you look back on any 325 00:20:38,880 --> 00:20:41,840 Speaker 1: of your beliefs from a decade ago, you can sometimes 326 00:20:41,880 --> 00:20:44,520 Speaker 1: see there have been some changes. But again, we tend 327 00:20:44,560 --> 00:20:46,960 Speaker 1: to assume that our current values are now locked into 328 00:20:46,960 --> 00:20:50,200 Speaker 1: place for the rest of our lives. We all fail 329 00:20:50,320 --> 00:20:54,119 Speaker 1: to anticipate that our worldview is going to continue to 330 00:20:54,160 --> 00:20:59,600 Speaker 1: get reshaped by life experiences, by new information, by changing 331 00:20:59,640 --> 00:21:04,520 Speaker 1: social contexts. In a decade, we might not be precisely 332 00:21:04,600 --> 00:21:23,520 Speaker 1: who we are right now. Now, this whole end of 333 00:21:23,600 --> 00:21:27,320 Speaker 1: history illusion wouldn't really matter for our lives, except that 334 00:21:27,359 --> 00:21:30,760 Speaker 1: it affects how we make decisions. Because so much of 335 00:21:30,760 --> 00:21:36,120 Speaker 1: what you do is in service to the assumed future you. 336 00:21:36,119 --> 00:21:40,280 Speaker 1: You suffer through courses and trainings now to make things 337 00:21:40,359 --> 00:21:44,440 Speaker 1: better for your future you. You sweat through a workout 338 00:21:44,520 --> 00:21:47,679 Speaker 1: so your future you will have a better body. You 339 00:21:47,720 --> 00:21:50,639 Speaker 1: put your money into retirement plans to make sure that 340 00:21:50,680 --> 00:21:54,919 Speaker 1: the future you has the resources that you predict that 341 00:21:54,960 --> 00:21:58,840 Speaker 1: stranger will need. The difficulty simply is that we're not 342 00:21:59,000 --> 00:22:02,040 Speaker 1: good predictors. You don't really know who that person is. 343 00:22:02,880 --> 00:22:06,320 Speaker 1: That person shares your name and your history, but the 344 00:22:06,400 --> 00:22:09,919 Speaker 1: fact is that person might be very different than the 345 00:22:10,040 --> 00:22:14,280 Speaker 1: current you. So you're donating your retirement money for this 346 00:22:14,440 --> 00:22:18,919 Speaker 1: future person that you can essentially guarantee will be not 347 00:22:19,200 --> 00:22:22,960 Speaker 1: who you currently believe. That person might vote for the 348 00:22:23,160 --> 00:22:25,880 Speaker 1: other political party, the what you would never vote for 349 00:22:26,119 --> 00:22:29,320 Speaker 1: and yet you're slaving away and handing over all your 350 00:22:29,480 --> 00:22:33,080 Speaker 1: money to that maniac. And you also do stuff assuming 351 00:22:33,600 --> 00:22:36,679 Speaker 1: the best about your future self, but sometimes that's not 352 00:22:36,880 --> 00:22:39,680 Speaker 1: useful either. We tend to assume that our future self 353 00:22:39,720 --> 00:22:43,880 Speaker 1: will be more motivated or disciplined than we are today. 354 00:22:44,359 --> 00:22:47,000 Speaker 1: So because of that, you might sign up for an 355 00:22:47,040 --> 00:22:51,320 Speaker 1: expensive gym membership believing that you'll be more committed in 356 00:22:51,320 --> 00:22:54,320 Speaker 1: the future, but then you don't really follow through. Your 357 00:22:54,359 --> 00:22:58,040 Speaker 1: future self isn't as on board with the plan as 358 00:22:58,080 --> 00:23:02,200 Speaker 1: your past self believed it would be. As a related example, 359 00:23:02,440 --> 00:23:06,200 Speaker 1: I'm chronically over committed because at every moment I assume 360 00:23:06,600 --> 00:23:09,439 Speaker 1: that my future self is going to be less busy 361 00:23:09,520 --> 00:23:11,879 Speaker 1: than I am now, and so I say yes to 362 00:23:11,960 --> 00:23:16,720 Speaker 1: future invitations or obligations like taking on big new projects 363 00:23:16,800 --> 00:23:20,600 Speaker 1: or attending multiple social events, And when the time arrives, 364 00:23:21,080 --> 00:23:25,120 Speaker 1: my future me wishes that my past me hadn't over committed. 365 00:23:26,000 --> 00:23:30,760 Speaker 1: And more generally, we fall victim to lots of planning fallacies. 366 00:23:30,800 --> 00:23:33,800 Speaker 1: We underestimate how long it's going to take to complete 367 00:23:34,040 --> 00:23:37,159 Speaker 1: some task. You might think cool, I can knock that 368 00:23:37,200 --> 00:23:38,960 Speaker 1: thing out in a week, and then you find that 369 00:23:39,000 --> 00:23:42,200 Speaker 1: it takes twice as long now. That happens because we 370 00:23:42,560 --> 00:23:47,040 Speaker 1: typically fail to correctly predict all the possible setbacks and 371 00:23:47,119 --> 00:23:50,840 Speaker 1: complexities that will run into in the future. My favorite 372 00:23:50,880 --> 00:23:54,920 Speaker 1: example of a planning fallacy is with a gentleman named 373 00:23:55,000 --> 00:23:58,760 Speaker 1: James Murray who in eighteen seventy eight set out to 374 00:23:58,880 --> 00:24:02,679 Speaker 1: write the for the English Dictionary, and the idea was 375 00:24:02,720 --> 00:24:05,720 Speaker 1: to capture all the words in the English speaking world 376 00:24:06,040 --> 00:24:10,159 Speaker 1: and give definitions for all of their various shades of meaning. 377 00:24:10,760 --> 00:24:13,160 Speaker 1: And this seemed like a big undertaking, but not big 378 00:24:13,280 --> 00:24:15,479 Speaker 1: enough that he couldn't complete it in a few years. 379 00:24:16,200 --> 00:24:20,520 Speaker 1: So he worked on this for thirty six years until 380 00:24:20,560 --> 00:24:23,919 Speaker 1: he died, and then several editors took up the mantle 381 00:24:24,040 --> 00:24:27,560 Speaker 1: after him, and the first edition of the Oxford English 382 00:24:27,640 --> 00:24:33,720 Speaker 1: Dictionary was finally completed seventy years after he began. He 383 00:24:33,920 --> 00:24:38,439 Speaker 1: totally misapprehended the size of the project, and if I 384 00:24:38,520 --> 00:24:41,840 Speaker 1: were here, I presumably would have done the same. So 385 00:24:41,960 --> 00:24:45,560 Speaker 1: as a result of this sort of planning fallacy, we're 386 00:24:45,600 --> 00:24:50,399 Speaker 1: constantly making decisions that our future selves are going to 387 00:24:50,440 --> 00:24:54,440 Speaker 1: regret or disagree with. Why. It's not because we're idiots now, 388 00:24:54,840 --> 00:24:58,719 Speaker 1: but instead because our circumstances and our preferences and our 389 00:24:58,720 --> 00:25:02,879 Speaker 1: priorities are to change over time. Okay, so let me 390 00:25:03,000 --> 00:25:05,840 Speaker 1: zoom back out to the big picture. We are creatures 391 00:25:05,920 --> 00:25:09,600 Speaker 1: who live and change through time, but we're yoked with 392 00:25:09,680 --> 00:25:13,640 Speaker 1: this illusion that we are unchanging, and so we misremember 393 00:25:13,720 --> 00:25:17,200 Speaker 1: our past and we work hard for future versions of 394 00:25:17,240 --> 00:25:20,480 Speaker 1: ourselves who we assume will be like us, but they 395 00:25:20,520 --> 00:25:23,200 Speaker 1: may not be. And by the way, there are all 396 00:25:23,320 --> 00:25:26,560 Speaker 1: kinds of complex relationships between your future self and your 397 00:25:26,600 --> 00:25:29,680 Speaker 1: past self through time, so it gets pretty crowded. Your 398 00:25:29,720 --> 00:25:32,359 Speaker 1: past self says, oh, I'm not gonna worry about my 399 00:25:32,440 --> 00:25:35,159 Speaker 1: future self, and your future self looks back and says, 400 00:25:35,400 --> 00:25:38,239 Speaker 1: what a jerk like. When people make the decision in 401 00:25:38,320 --> 00:25:42,639 Speaker 1: the short term to postpone their education or splurge on 402 00:25:42,680 --> 00:25:46,359 Speaker 1: some overpriced thing, and then your future self thinks, dang, 403 00:25:46,400 --> 00:25:49,240 Speaker 1: I wish I'd gone to that class or spent my 404 00:25:49,400 --> 00:25:53,800 Speaker 1: money on something more meaningful or necessary. This comes up 405 00:25:53,840 --> 00:25:56,760 Speaker 1: for many people. In terms of retirement savings. People will 406 00:25:56,840 --> 00:25:59,359 Speaker 1: make the decision to spend now rather than save for 407 00:25:59,400 --> 00:26:03,280 Speaker 1: their future self. They keep thinking, oh, I'll start saving later, 408 00:26:03,720 --> 00:26:07,520 Speaker 1: But then as retirement approaches, your future self feels mad 409 00:26:07,560 --> 00:26:09,479 Speaker 1: at your past self and wished as you had started 410 00:26:09,480 --> 00:26:12,840 Speaker 1: saving earlier, and I suspect this is true. Anytime we 411 00:26:12,960 --> 00:26:16,960 Speaker 1: choose instant gratification over long term goals, our future selves 412 00:26:17,000 --> 00:26:19,119 Speaker 1: look back and they're mad about it. And all this 413 00:26:19,280 --> 00:26:24,440 Speaker 1: highlights the challenge of balancing short term desires with long 414 00:26:24,560 --> 00:26:27,600 Speaker 1: term outcomes. In other words, your self in the moment 415 00:26:27,720 --> 00:26:31,840 Speaker 1: now versus yourself in the future. So let's wrap up. 416 00:26:32,359 --> 00:26:34,680 Speaker 1: In the next episode, Part two, we're going to dive 417 00:26:34,800 --> 00:26:38,200 Speaker 1: deeper into all these paradoxes of the self by talking 418 00:26:38,200 --> 00:26:42,119 Speaker 1: with my colleague neuroscientist Mike Levin, who wrote a recent 419 00:26:42,160 --> 00:26:45,199 Speaker 1: paper in which he pointed out that quote if we 420 00:26:45,440 --> 00:26:49,879 Speaker 1: do not change, learning and growth is impossible. If we 421 00:26:50,280 --> 00:26:54,359 Speaker 1: do change, does not the current self cease to exist 422 00:26:54,920 --> 00:26:58,920 Speaker 1: in an important sense end quote. So let's summarize where 423 00:26:58,920 --> 00:27:01,520 Speaker 1: we got in this episode. We began by looking at 424 00:27:01,560 --> 00:27:05,359 Speaker 1: the illusion of continuity, and we use the ancient thought 425 00:27:05,400 --> 00:27:08,560 Speaker 1: experiment of the ship of Theseus, where one plank of 426 00:27:08,600 --> 00:27:10,520 Speaker 1: the ship gets replaced at a time, and we can 427 00:27:10,560 --> 00:27:14,320 Speaker 1: ask is it still the ship of theseus after every 428 00:27:14,359 --> 00:27:17,880 Speaker 1: plank has been replaced. We looked at this question because 429 00:27:18,119 --> 00:27:22,000 Speaker 1: we are always surfing on top of constant physical changes, 430 00:27:22,400 --> 00:27:27,240 Speaker 1: and yet we perceive ourselves as consistent over time. The 431 00:27:27,280 --> 00:27:30,760 Speaker 1: planks and theseus's ship are the cells and molecules in 432 00:27:30,800 --> 00:27:34,600 Speaker 1: your body, and this foregrounds the question about what makes 433 00:27:34,680 --> 00:27:38,960 Speaker 1: you the same person over time. We asked the question 434 00:27:39,040 --> 00:27:41,520 Speaker 1: of whether we can really say that memory is the 435 00:27:41,680 --> 00:27:45,640 Speaker 1: thread holding identity together, because the truth is that memory 436 00:27:45,760 --> 00:27:51,719 Speaker 1: is far from reliable. It's constantly being rewritten. And finally, 437 00:27:51,760 --> 00:27:54,480 Speaker 1: we touched on a cognitive bias known as the end 438 00:27:54,480 --> 00:27:58,359 Speaker 1: of history illusion, which is where we massively underestimate how 439 00:27:58,440 --> 00:28:00,399 Speaker 1: much we're going to change in the future, even though 440 00:28:00,400 --> 00:28:03,400 Speaker 1: we're aware that we've changed in the past. We tend 441 00:28:03,440 --> 00:28:07,720 Speaker 1: to believe that our current tastes and values and personalities 442 00:28:07,720 --> 00:28:11,080 Speaker 1: are going to remain consistent from here on out, even 443 00:28:11,200 --> 00:28:16,199 Speaker 1: though we keep on changing throughout our lives. So you 444 00:28:16,240 --> 00:28:19,480 Speaker 1: can't actually be your past self. But as we'll see 445 00:28:19,680 --> 00:28:23,639 Speaker 1: in part two next week, we constantly try to reconstruct 446 00:28:23,640 --> 00:28:28,800 Speaker 1: that person. We constantly try to revivify that past self 447 00:28:28,880 --> 00:28:33,399 Speaker 1: based on the evidence provided by reinterpreting the clues that 448 00:28:33,440 --> 00:28:36,439 Speaker 1: are left by them. In other words, the memories that 449 00:28:36,480 --> 00:28:40,720 Speaker 1: are buried in the neural network. In this view, memories 450 00:28:40,800 --> 00:28:43,960 Speaker 1: are like a message in a bottle thrown from your 451 00:28:44,200 --> 00:28:48,479 Speaker 1: present self into the ocean for someone to find, and 452 00:28:48,520 --> 00:28:53,440 Speaker 1: that someone is a future you who you don't necessarily know. 453 00:28:57,480 --> 00:29:00,560 Speaker 1: Go to Eagleman dot com slash podcast for more information 454 00:29:00,800 --> 00:29:03,800 Speaker 1: and to find further reading. Send me an email at 455 00:29:03,840 --> 00:29:07,200 Speaker 1: podcasts at eagleman dot com with questions or discussion and 456 00:29:07,320 --> 00:29:10,520 Speaker 1: check out Subscribe to Inner Cosmos on YouTube for videos 457 00:29:10,520 --> 00:29:13,760 Speaker 1: of each episode and to leave comments until next time. 458 00:29:13,920 --> 00:29:18,800 Speaker 1: I'm David Eagleman and this is Inner at Cosmos.