WEBVTT - Ep70 Re Broadcast "Why do our memories drift? Part 1: The War of the Ghosts" 0:00:05.040 --> 0:00:08.760 When you look at medieval European art, why do the 0:00:08.840 --> 0:00:13.440 people look fine but the lions look so strange? And 0:00:13.480 --> 0:00:16.720 what does this have to do with Native American folklore 0:00:17.200 --> 0:00:20.959 or I witness memory of a car accident, or what 0:00:21.079 --> 0:00:25.720 a person remembers three years after watching the nine to 0:00:25.760 --> 0:00:28.680 eleven attack on the World Trade Center, And what does 0:00:28.720 --> 0:00:32.239 any of this have to do with flashbulb memories or 0:00:32.320 --> 0:00:37.320 misinformation or the telephone game that you played as a child. 0:00:40.720 --> 0:00:43.760 Welcome to Inner Cosmos with me, David Eagleman. I'm a 0:00:43.800 --> 0:00:47.320 neuroscientist and an author at Stanford, and in these episodes 0:00:47.440 --> 0:00:50.960 we sail deeply into our three pound universe to understand 0:00:51.120 --> 0:00:54.520 why and how our lives look the way they do. 0:00:55.120 --> 0:00:58.400 Today's episode is part one of a two parter about 0:00:58.600 --> 0:01:05.080 memory and why it rifts. So I want to start 0:01:05.120 --> 0:01:08.200 with this fascinating observation that you can notice if you 0:01:08.319 --> 0:01:12.760 look across visual painting in Europe all through the Middle Ages. 0:01:13.440 --> 0:01:17.840 Painters got better and better through time at painting architecture 0:01:18.200 --> 0:01:22.320 and the human form and mountain scapes, but they were 0:01:22.400 --> 0:01:27.160 absolutely terrible at painting lions. If you look at lions 0:01:27.319 --> 0:01:30.720 in these medieval paintings, you'll see that they generally look 0:01:30.959 --> 0:01:36.240 quite different from their real life counterparts. They have exaggerated 0:01:36.319 --> 0:01:40.679 features like overly large heads and bodies that are too long, 0:01:41.319 --> 0:01:45.720 and tufted tails that aren't really like actual lion tails, 0:01:46.160 --> 0:01:49.240 and they often look more like large, fierce dogs or 0:01:49.280 --> 0:01:53.200 mythical creatures. I'll put some pictures on eagleman dot com 0:01:53.200 --> 0:01:57.080 slash podcasts so you can see how strange these lions are. 0:01:57.480 --> 0:02:02.160 But why is this? The answer is the medieval European 0:02:02.240 --> 0:02:06.080 painters spent a lot of time with architecture and with 0:02:06.400 --> 0:02:09.839 people and with mountainscapes, but almost none of them had 0:02:09.919 --> 0:02:14.040 ever been to Africa and therefore seen a real lion, 0:02:14.480 --> 0:02:16.400 or for that matter, had been to India and seen 0:02:16.400 --> 0:02:21.440 an asiatic lion. So they had the extremely tough challenge 0:02:21.480 --> 0:02:26.080 of painting something they had never actually seen. Now, to 0:02:26.160 --> 0:02:29.160 be clear, it's not that they had never seen a lion, 0:02:29.200 --> 0:02:32.160 it's that they had never seen a real lion. All 0:02:32.200 --> 0:02:35.920 they had ever seen were versions of lions painted by 0:02:36.000 --> 0:02:40.320 other medieval painters, who presumably had seen pictures of lions 0:02:40.320 --> 0:02:43.400 painted by other medieval painters, and so on back to 0:02:43.919 --> 0:02:47.840 someone who had at some point seen a real lion, 0:02:48.280 --> 0:02:51.320 and so This notion of what a lion looks like 0:02:51.800 --> 0:02:56.160 gives us a visual example of the operator game. This 0:02:56.280 --> 0:02:59.880 is also known as the telephone game or Russian scandal 0:03:00.320 --> 0:03:02.800 or pass the secret. So you remember doing this as 0:03:02.840 --> 0:03:05.880 a kid. One person whispers, let's say a word or 0:03:05.919 --> 0:03:08.720 a little phrase in your ear, and then you whisper 0:03:08.800 --> 0:03:11.080 it to the next person, and they whisper it to 0:03:11.160 --> 0:03:13.360 the next person, and so on, and by the time 0:03:13.440 --> 0:03:16.120 it gets to the last person, she shouts it out 0:03:16.360 --> 0:03:18.600 and you all get to see if it's the same 0:03:18.720 --> 0:03:22.000 word or phrase that the first person said. And the 0:03:22.120 --> 0:03:24.720 joy of the game, of course, is that the message 0:03:24.760 --> 0:03:28.079 gets distorted in transmission, and by the time it ends 0:03:28.160 --> 0:03:31.320 up somewhere it can be very different from how it began. 0:03:32.320 --> 0:03:35.560 So today and next week we're going to dive into 0:03:35.680 --> 0:03:40.960 a strange question, how your own memories are like the 0:03:41.040 --> 0:03:45.680 Operator game. In other words, we tend to erroneously believe 0:03:45.880 --> 0:03:49.200 that when something happens, we record that in the brain. 0:03:49.280 --> 0:03:53.240 It's written down in the brain as a memory, the 0:03:53.240 --> 0:03:56.080 way that a computer might hold a little file. And 0:03:56.080 --> 0:03:59.240 then every time we retrieve that memory, every time we 0:03:59.320 --> 0:04:02.600 pull that back up, we are viewing that little movie again. 0:04:03.240 --> 0:04:06.080 So it comes as a surprise that real human memory 0:04:06.120 --> 0:04:08.640 in the brain is nothing like a movie, but much 0:04:08.680 --> 0:04:14.640 more like the Operator game, wherein the message becomes increasingly distorted. 0:04:14.800 --> 0:04:17.800 For example, let's say I show you a picture of 0:04:17.839 --> 0:04:21.080 something that you're not super familiar with, like an old 0:04:21.480 --> 0:04:24.920 Polynesian war mass with a sort of strange shape in 0:04:24.960 --> 0:04:27.240 some different lines and circles on it, and then I 0:04:27.320 --> 0:04:32.120 ask you to draw it. Later, your drawing will probably 0:04:32.279 --> 0:04:35.159 drift from what you actually saw, and the next time 0:04:35.240 --> 0:04:37.560 after that, when I ask you to draw it again, 0:04:38.240 --> 0:04:41.880 your memory will presumably be influenced by what you drew 0:04:42.000 --> 0:04:44.440 the last time. And if I ask you to do 0:04:44.480 --> 0:04:46.920 this over and over again, let's say once a month, 0:04:47.000 --> 0:04:51.120 there will be something of a steady progression from drawing 0:04:51.200 --> 0:04:55.560 one to drawing ten, because you are playing the operator 0:04:55.640 --> 0:05:00.120 game with yourself. Each time you retrieve the memory, it 0:05:00.200 --> 0:05:03.239 is influenced by what you thought it was last time. 0:05:03.520 --> 0:05:06.160 So to dig into this, we're going to start today's 0:05:06.200 --> 0:05:10.160 episode with a short story. This is a Native American 0:05:10.440 --> 0:05:14.400 folk story called the War of the Ghosts, and it's 0:05:14.440 --> 0:05:16.480 read here by actor Sean Judge. 0:05:17.080 --> 0:05:21.560 War of the Ghosts. One night, two young men from 0:05:21.640 --> 0:05:24.760 Eguilak went down to the river to hunt seals, and 0:05:24.839 --> 0:05:28.960 while they were there it became foggy and calm. Then 0:05:29.400 --> 0:05:32.720 they heard war cries and they thought maybe this is 0:05:32.760 --> 0:05:35.920 a war party. They escaped to the shore and hid 0:05:35.960 --> 0:05:39.599 behind a log. Now canoes came up, and they heard 0:05:39.640 --> 0:05:42.440 the noise of paddles and saw one canoe coming up 0:05:42.520 --> 0:05:45.560 to them. There were five men in the canoe, and 0:05:45.640 --> 0:05:48.680 they said, what do you think we wish to take 0:05:48.720 --> 0:05:50.760 you along. We are going up the river to make 0:05:50.800 --> 0:05:53.880 war on the people. One of the young men said, 0:05:54.480 --> 0:05:58.160 I have no arrows. Arrows are in the canoe. They said, 0:05:59.120 --> 0:06:01.720 I will not go along. I might be killed. My 0:06:01.839 --> 0:06:04.520 relatives do not know where I have gone. But you, 0:06:04.880 --> 0:06:07.160 he said, turning to the other, may go with them. 0:06:08.279 --> 0:06:10.760 So one of the young men went, but the other 0:06:10.839 --> 0:06:14.800 returned home, and the warriors went on up the river 0:06:14.920 --> 0:06:17.760 to a town on the other side of Kalama. The 0:06:17.800 --> 0:06:20.119 people came down to the water and they began to fight, 0:06:20.320 --> 0:06:23.960 and many were killed. But presently the young man heard 0:06:24.000 --> 0:06:26.840 one of the warriors say, quick, let us go home. 0:06:27.160 --> 0:06:31.960 That Indian has been hit. Now he thought, oh, they 0:06:32.000 --> 0:06:36.080 are ghosts. He did not feel sick, but they said 0:06:36.160 --> 0:06:40.120 he had been shot. So the canoes went back to Aguilak, 0:06:40.279 --> 0:06:42.400 and the young man went ashore to his house and 0:06:42.440 --> 0:06:46.400 made a fire, and he told everybody and said, behold, 0:06:46.839 --> 0:06:49.960 I accompanied the ghosts, and we went to fight. Many 0:06:50.040 --> 0:06:52.160 of our fellows were killed, and many of those who 0:06:52.200 --> 0:06:55.279 attacked us were killed. They said, I was hit, but 0:06:55.360 --> 0:06:58.760 I did not feel sick. He told it all, and 0:06:58.800 --> 0:07:03.320 then he became quiet. When the sun rose, he fell down. 0:07:04.279 --> 0:07:08.640 Something black came out of his mouth, his face became contorted. 0:07:09.360 --> 0:07:12.840 The people jumped up and cried he was dead. 0:07:13.640 --> 0:07:16.400 This probably seems to you like a bit of a 0:07:16.440 --> 0:07:20.760 weird story. It seems like it's not particularly well told 0:07:20.840 --> 0:07:25.120 or clear. So given the strangeness of the story, why 0:07:25.120 --> 0:07:29.000 did it become quite famous in the psychology community almost 0:07:29.040 --> 0:07:32.120 a century ago in nineteen thirty two. It's because of 0:07:32.160 --> 0:07:36.560 a researcher named Frederick Bartlett, who was a psychologist at 0:07:36.600 --> 0:07:40.640 Cambridge University. He chose this story, the War of the Ghosts, 0:07:41.080 --> 0:07:45.960 to examine the way that our memories change with time. Now, 0:07:46.000 --> 0:07:49.000 he chose this particular folk tale because he wanted something 0:07:49.040 --> 0:07:52.560 that wasn't crystal clear, so that it might be slightly 0:07:52.640 --> 0:07:57.440 more susceptible to changes in the retelling. That way, he 0:07:57.480 --> 0:08:01.520 could examine the way in which it changed in the retelling, 0:08:01.880 --> 0:08:04.760 and the retelling after that, and so on into the future. 0:08:04.880 --> 0:08:08.000 In other words, he used this story to see if 0:08:08.000 --> 0:08:12.920 he could really shine a light on the constructive character 0:08:13.000 --> 0:08:15.800 of memory. In other words, the way that recalling a 0:08:15.840 --> 0:08:22.360 memory is something like reconstructing what happened your brain rebuilding 0:08:22.360 --> 0:08:25.320 its best guess at a memory, rather than the way 0:08:25.400 --> 0:08:29.000 a computer simply retrieves a file of zeros and ones 0:08:29.040 --> 0:08:33.439 without loss. So in Bartlett's study, he had participants read 0:08:33.640 --> 0:08:36.600 the War of the Ghosts. Then they were instructed to 0:08:36.679 --> 0:08:40.280 recall and write down the story as perfectly as they could. 0:08:41.160 --> 0:08:43.559 Now it's only been about a minute since you heard 0:08:43.640 --> 0:08:47.400 the story, Think about how you would retell it now, 0:08:47.480 --> 0:08:51.160 what details you would remember from that story. Not surprisingly, 0:08:51.240 --> 0:08:55.480 Bartlett found that the story drifted from the original upon 0:08:55.600 --> 0:08:59.000 the retelling. Here, for example, is a person who is 0:08:59.080 --> 0:09:03.120 asked to remember and reproduce the story, and he did 0:09:03.120 --> 0:09:07.199 this multiple times. Here he is on his tenth reproduction. 0:09:07.080 --> 0:09:10.440 War of the Ghosts. Two Indians were out fishing for 0:09:10.520 --> 0:09:13.760 seals in the Bay of Manpapan when along came five 0:09:13.840 --> 0:09:17.360 other Indians in a war canoe. They were going fighting. 0:09:18.120 --> 0:09:20.520 Come with us, said five of the two, and fight. 0:09:21.440 --> 0:09:23.760 I cannot come, was the answer of the one, for 0:09:23.880 --> 0:09:25.760 I have an old mother at home who has dependent 0:09:25.840 --> 0:09:28.560 on me. The other also said he could not come 0:09:28.640 --> 0:09:31.880 because he had no arms. That is no difficulty. The 0:09:31.920 --> 0:09:34.800 others replied, for we have plenty in the canoe with us. 0:09:35.640 --> 0:09:38.840 So he got into the canoe and went with them 0:09:39.120 --> 0:09:42.760 in a fight. Soon afterwards, this Indian received a mortal wound. 0:09:43.679 --> 0:09:46.240 Finding that his hour was come, he cried out that 0:09:46.280 --> 0:09:49.440 he was about to die. Nonsense, said one of the others. 0:09:49.720 --> 0:09:53.079 You will not die, But he did now. 0:09:53.160 --> 0:09:56.400 Bartlett also had other participants read the story and then 0:09:56.480 --> 0:09:59.960 reproduce it at intervals very far apart. In some cases 0:10:00.000 --> 0:10:03.760 this is over years. So here's another participant. This is 0:10:03.920 --> 0:10:07.720 subject p on his first reproduction. 0:10:07.679 --> 0:10:11.560 War of the Ghosts. Two youths were standing by a 0:10:11.640 --> 0:10:14.560 river about to start seal catching when a boat appeared 0:10:14.559 --> 0:10:17.960 with five men in it. They were all armed for war. 0:10:18.880 --> 0:10:21.760 The youths were at first frightened, but they were asked 0:10:21.800 --> 0:10:23.720 by the men to come and help them fight some 0:10:23.880 --> 0:10:26.720 enemies on the other bank. One youth said that he 0:10:26.720 --> 0:10:29.320 could not come, as his relations would be anxious about him. 0:10:29.840 --> 0:10:32.360 The other said he would go and entered the boat. 0:10:33.320 --> 0:10:35.880 In the evening, he returned to his hut and told 0:10:35.920 --> 0:10:38.800 his friends that he had been in a battle. A 0:10:38.880 --> 0:10:41.800 great many had been slain, and he had been wounded 0:10:41.840 --> 0:10:44.959 by an arrow. He had not felt any pain, he said. 0:10:45.640 --> 0:10:47.440 They told him that he must have been fighting a 0:10:47.480 --> 0:10:51.920 battle of ghosts. Then he remembered that it had been queer, 0:10:52.240 --> 0:10:56.439 and he was very excited. In the morning, however, he 0:10:56.480 --> 0:11:00.720 became ill, and his friends gathered round. He fell down 0:11:00.840 --> 0:11:05.880 and his face became very pale. Then he writhed and shrieked, 0:11:06.240 --> 0:11:09.920 and his friends were filled with terror. At last he 0:11:10.000 --> 0:11:14.679 became calm. Something hard and black came out of his mouth, 0:11:15.480 --> 0:11:17.839 and he lay contorted and dead. 0:11:18.360 --> 0:11:21.760 And here he is again when he's asked to reproduce 0:11:21.840 --> 0:11:24.160 the story. After thirty months. 0:11:24.520 --> 0:11:28.600 War of the ghosts, some warriors went to wage war 0:11:28.679 --> 0:11:31.760 against the ghosts. They fought all day, and one of 0:11:31.800 --> 0:11:35.280 their number was wounded. They returned home in the evening 0:11:35.600 --> 0:11:39.240 bearing their sick comrade. As the day drew to a close, 0:11:39.400 --> 0:11:42.520 he became rapidly worse, and the villagers came round him. 0:11:43.520 --> 0:11:47.480 As sunset, he sighed something black came out of his mouth. 0:11:48.880 --> 0:12:00.280 He was dead. 0:12:05.320 --> 0:12:08.120 So what he generally found is that the story became 0:12:08.600 --> 0:12:12.200 shorter with each reproduction. But here was the key. He 0:12:12.320 --> 0:12:15.640 realized that this was more than just the telephone game, 0:12:15.920 --> 0:12:21.040 where a signal just becomes noisier each time it's repeated. Instead, 0:12:21.080 --> 0:12:23.720 with the War of the Ghosts, he found there was 0:12:23.800 --> 0:12:27.840 a pattern to the way the story changed. First of all, 0:12:28.240 --> 0:12:33.920 it typically became more coherent to the speaker, as Bartlett wrote, 0:12:34.200 --> 0:12:39.000 quote no trace of an odd or supernatural element is left. 0:12:39.240 --> 0:12:43.440 We have a perfectly straightforward story of a fight and 0:12:43.559 --> 0:12:47.880 a death end quote. So Bartlett studied the character of 0:12:47.920 --> 0:12:52.640 the changes, and he found that these happened by transforming 0:12:52.800 --> 0:12:57.120 details into things that are more familiar and conventional to 0:12:57.280 --> 0:13:01.400 the person doing the remembering. Sometimes the order of events 0:13:01.440 --> 0:13:05.640 would change, and things would commonly get omitted, like the 0:13:05.679 --> 0:13:08.480 ghosts getting sliced out of the story pretty early on, 0:13:09.120 --> 0:13:13.040 or the wound becoming a matter of flesh not spirit. 0:13:13.559 --> 0:13:16.240 All in all, he was interested in the way that people, 0:13:16.760 --> 0:13:21.199 through time made the parts grow more coherent for themselves. 0:13:21.200 --> 0:13:26.280 In other words, the distortions were driven by a person's schema. Now, 0:13:26.280 --> 0:13:28.520 what does that mean. It means that people morphed the 0:13:28.559 --> 0:13:32.160 story to make it consistent with what's going on in 0:13:32.200 --> 0:13:35.240 their heads. In other words, the changes you make to 0:13:35.280 --> 0:13:38.520 the story are navigated by your internal model, or what 0:13:38.559 --> 0:13:44.559 psychologists call your schema, your mental framework for organizing knowledge 0:13:44.720 --> 0:13:49.439 and guiding perception. This is your brain's unique way of 0:13:49.559 --> 0:13:53.080 seeing the world. So the way the story was distorted 0:13:53.520 --> 0:13:56.440 in terms of the plot and characters and events is 0:13:56.559 --> 0:14:00.280 different in your brain versus someone else's brain. There's a 0:14:00.280 --> 0:14:04.800 lot of differences between individual schema, which is to say, 0:14:04.920 --> 0:14:07.920 if you read the story to someone who's really into boats, 0:14:07.960 --> 0:14:11.400 they might remember something differently than someone who's really into 0:14:11.800 --> 0:14:15.280 Native American history, or someone who's a physician and thinks 0:14:15.320 --> 0:14:18.640 about what causes a person to die. And by the way, 0:14:18.679 --> 0:14:22.680 it's not just individual differences, but also your culture plays 0:14:22.680 --> 0:14:26.200 a massive role in shaping the way that you interpret 0:14:26.240 --> 0:14:31.080 and remember information. So as you recall a story, you 0:14:31.520 --> 0:14:35.520 unconsciously mold it to align with your cultural background and 0:14:35.560 --> 0:14:39.120 your beliefs and your expectations. So this all has to 0:14:39.120 --> 0:14:43.120 do with the differences in internal models. Bartlet's study the 0:14:43.160 --> 0:14:47.480 way that people can't label something until it is recognizable, 0:14:47.840 --> 0:14:52.920 So transformations moved in the direction of the conventions in 0:14:52.960 --> 0:14:57.360 their head. So I think about Bartlett's study all the time, 0:14:57.480 --> 0:15:01.560 for example, and how we consume news. Any news story 0:15:01.600 --> 0:15:05.640 we read this month is remembered differently by you than 0:15:05.680 --> 0:15:09.600 by someone else who reads it through a different political lens. 0:15:10.240 --> 0:15:12.640 Watch anything on the news, and then talk to anyone 0:15:12.680 --> 0:15:15.480 you know who sees the world a little differently, and 0:15:15.520 --> 0:15:19.400 you'll find that it's not impossible that they remember different 0:15:19.440 --> 0:15:22.040 parts of the story than you did, and or they 0:15:22.080 --> 0:15:27.680 remembered them differently. Their distortions in the story are not accidental, 0:15:27.760 --> 0:15:31.480 and nor are yours. They are ways of making things 0:15:31.680 --> 0:15:36.320 internally consistent. Now, psychologists have a lot of ways of 0:15:36.440 --> 0:15:41.000 talking about this, like confirmation bias, which means we tend 0:15:41.040 --> 0:15:45.160 to seek out and remember information that is consistent with 0:15:45.280 --> 0:15:48.480 our internal models, and there are other ways of talking 0:15:48.480 --> 0:15:52.160 about this. I recently did an episode on conspiracy theories, 0:15:52.360 --> 0:15:55.120 and one of the things I highlighted is the way 0:15:55.120 --> 0:15:58.880 that we are attracted to theories that reduce our cognitive 0:15:58.920 --> 0:16:02.160 load or our cog of dissonance. In other words, we 0:16:02.320 --> 0:16:05.920 prefer a clear and easy story, and all this is 0:16:06.000 --> 0:16:10.080 consistent with what Bartlett found in nineteen thirty two. We 0:16:10.240 --> 0:16:13.400 don't remember the story as it is presented to us, 0:16:13.840 --> 0:16:17.840 but rather as our filters allow us to store it 0:16:17.960 --> 0:16:21.920 and recall it. And when I think about the driftiness 0:16:22.080 --> 0:16:25.560 of memory, there are other angles that need to be surfaced. 0:16:25.600 --> 0:16:27.400 And here's the main thing that we're going to talk 0:16:27.400 --> 0:16:32.760 about today. Rather than memory being an accurate video recording 0:16:32.920 --> 0:16:35.880 of a moment in your life, it is a fragile 0:16:36.200 --> 0:16:39.760 brain state from a bygone time that has to be 0:16:40.240 --> 0:16:45.280 resurrected for you to remember. So here's an example. You're 0:16:45.360 --> 0:16:48.720 at a restaurant with a couple that you know who 0:16:48.840 --> 0:16:54.160 are visiting town, and everything you experience triggers particular patterns 0:16:54.200 --> 0:16:57.760 of activity in your brain. For example, there's a particular 0:16:58.000 --> 0:17:02.040 pattern of activity sparked into life by the conversation between 0:17:02.080 --> 0:17:05.680 you and your friends. Another pattern is activated by the 0:17:05.720 --> 0:17:09.680 smell of the coffee. Another pattern is activated by the 0:17:09.760 --> 0:17:13.479 taste of a madeleine cookie. The fact that the waiter 0:17:13.720 --> 0:17:16.560 is limping with a cast on his leg is another 0:17:17.080 --> 0:17:21.119 memorable detail, and that's represented by a different configuration of 0:17:21.160 --> 0:17:25.879 neurons firing. All of these constellations become linked with one another, 0:17:26.280 --> 0:17:31.440 in a vast network of neurons that the hippocampus replays 0:17:31.560 --> 0:17:36.399 over and over until the associations between these scattered neurons, 0:17:36.440 --> 0:17:40.479 these distant points of light, this all becomes fixed into place. 0:17:41.280 --> 0:17:44.640 The neurons that are active at the same time will 0:17:44.720 --> 0:17:50.320 establish stronger connections between them. Sells that fire together wire together. 0:17:50.880 --> 0:17:55.680 The resulting network is the unique signature of that event, 0:17:55.840 --> 0:18:00.919 and it represents your memory of the dinner with them. Now, 0:18:01.320 --> 0:18:04.600 let's imagine that six months later, you taste one of 0:18:04.640 --> 0:18:07.840 those Madeleine cookies just like the one you tasted at 0:18:07.880 --> 0:18:12.240 the dinner with the couple. This very specific key can 0:18:12.400 --> 0:18:18.280 unlock the whole web of associations. The original constellation lights 0:18:18.400 --> 0:18:21.719 up like the lights of a city coming online, and 0:18:21.880 --> 0:18:27.120 suddenly your back in that memory. But although we don't 0:18:27.160 --> 0:18:30.840 always realize it, the memory is not as rich as 0:18:30.880 --> 0:18:34.119 you might have expected. You know that your two friends 0:18:34.119 --> 0:18:36.600 were there, and he must have been wearing a button 0:18:36.680 --> 0:18:38.919 up shirt because he always wears a button up shirt, 0:18:39.400 --> 0:18:42.919 and she was wearing a blue dress, or maybe it 0:18:42.960 --> 0:18:46.879 was purple, might have been green. If you really probe 0:18:46.920 --> 0:18:50.360 the memory, you'll realize that you can't remember the details 0:18:50.359 --> 0:18:52.520 of any of the other diners at the restaurant, even 0:18:52.560 --> 0:18:56.240 though the place was full. So your memory of their 0:18:56.240 --> 0:19:01.240 dinner visit has started to fade. Why well, you have 0:19:01.320 --> 0:19:05.000 a finite number of neurons and they are each required 0:19:05.040 --> 0:19:09.680 to multitask. Every neuron in your head participates in different 0:19:09.800 --> 0:19:15.440 constellations at different times. Your neurons operate in a dynamic 0:19:15.720 --> 0:19:20.320 matrix of shifting relationships, and heavy demand is always placed 0:19:20.320 --> 0:19:23.840 on them to wire with others. So your memory of 0:19:23.880 --> 0:19:27.960 the dinner has become muddied as the neurons involved have 0:19:28.080 --> 0:19:33.199 become co opted to participate in other memory constellations. The 0:19:33.560 --> 0:19:39.320 enemy of memory isn't time, it's other memories. Each new 0:19:39.320 --> 0:19:44.359 event needs to establish new relationships among a finite number 0:19:44.400 --> 0:19:48.840 of neurons. Now, the surprise is that a faded memory 0:19:49.280 --> 0:19:53.640 doesn't feel faded to you. You assume, or at least 0:19:53.720 --> 0:19:57.320 you into it, that the full picture is there. And 0:19:57.400 --> 0:20:00.640 the situation is even worse than this, because because it's 0:20:00.680 --> 0:20:04.919 not just that the memory is fading, it's actually drifting. 0:20:05.400 --> 0:20:09.719 So imagine that in the intervening year since the dinner, 0:20:10.040 --> 0:20:14.119 your two friends have broken up. Thinking back on the dinner, 0:20:14.160 --> 0:20:20.280 you might now misremember sensing red flags. Wasn't he more 0:20:20.400 --> 0:20:24.120 quiet than usual that night? Weren't there moments of awkward 0:20:24.240 --> 0:20:27.399 silence between the two? Well, it'll be difficult to know 0:20:27.560 --> 0:20:31.200 for certain, because the knowledge that's in your network now, 0:20:31.600 --> 0:20:34.879 now that they've broken up, that changes the memory that 0:20:35.000 --> 0:20:40.160 corresponds to. Then you can't help but have your present 0:20:40.760 --> 0:20:46.040 color your past, so an event may be perceived somewhat 0:20:46.080 --> 0:20:50.080 differently by you at different moments in your life now. 0:20:50.200 --> 0:20:54.800 Psychologists have been studying the malleability of memory for many decades, 0:20:54.840 --> 0:20:58.000 and one of the pioneers in the field is Elizabeth 0:20:58.119 --> 0:21:02.199 Loftis at the University of California, Irvine. She transformed the 0:21:02.240 --> 0:21:07.000 field of memory research by showing how susceptible memories are. 0:21:07.280 --> 0:21:09.960 So one of her experiments goes like this. She has 0:21:10.040 --> 0:21:14.679 people watch films of car crashes and then she asks 0:21:14.720 --> 0:21:17.560 them a series of questions to test what they remembered. 0:21:17.880 --> 0:21:20.439 And what she found is that just the way she 0:21:20.800 --> 0:21:25.480 asks the question influences the answer she gets back. So 0:21:25.600 --> 0:21:28.920 if she asks how fast were the cars going when 0:21:28.920 --> 0:21:32.080 they hit each other, she gets an estimate of the speed. 0:21:32.440 --> 0:21:35.439 But if she asks how fast were the cars going 0:21:35.800 --> 0:21:40.439 when they smashed into each other, witnesses give a different estimate. 0:21:40.800 --> 0:21:45.000 Not surprisingly, they believe the cars were going faster when 0:21:45.040 --> 0:21:48.000 she uses the word smashed. Now, if you heard my 0:21:48.119 --> 0:21:51.760 episode on eyewitness testimony, you know that these sorts of 0:21:51.840 --> 0:21:54.479 problems are seen all the time in the legal system. 0:21:54.560 --> 0:21:59.679 For example, there's a related issue known as the misinformation 0:21:59.720 --> 0:22:03.120 of effect. If you witness an event, but then later 0:22:03.160 --> 0:22:05.520 you're told something about that event in terms of what 0:22:05.760 --> 0:22:08.359 happened at the scene, or who is there or what 0:22:08.400 --> 0:22:11.640 they look like, that will become part of your memory too, 0:22:12.000 --> 0:22:14.240 and you may not be able to distinguish what you've 0:22:14.280 --> 0:22:18.200 been told from what actually happened. So Loftus and her 0:22:18.240 --> 0:22:21.679 team study this, for example, by showing people a picture 0:22:21.720 --> 0:22:24.960 of a car at a stop sign, and then afterwards, 0:22:25.040 --> 0:22:28.639 after the picture is removed, they give a text description 0:22:28.760 --> 0:22:31.560 of the same picture, but in the text they say 0:22:31.640 --> 0:22:34.879 it was a yield sign. And then they have people 0:22:35.320 --> 0:22:38.840 draw the picture as they remember it, and people tend 0:22:38.880 --> 0:22:42.320 to draw the original scene with a yield sign. So 0:22:42.480 --> 0:22:46.920 even after an memory is encoded, new information coming in 0:22:47.440 --> 0:22:51.120 like that it was a yield sign will change the retrieval. 0:22:51.680 --> 0:22:54.639 You'll believe that the whole time you saw a yield 0:22:54.680 --> 0:23:13.000 sign there instead of a stop sign. Now all the 0:23:13.119 --> 0:23:16.280 sounds surprising at first. You think I can distinguish my 0:23:16.440 --> 0:23:20.680 own memory from something someone else said, But it turns 0:23:20.680 --> 0:23:24.119 out we can't. And we'll dive more into this in 0:23:24.160 --> 0:23:27.919 a quite shocking way in next week's episode. But I 0:23:27.960 --> 0:23:29.840 want to give you a deeper sense of this now, 0:23:29.880 --> 0:23:34.760 about the changeability of memories. So here's another problem. It's 0:23:34.800 --> 0:23:39.280 a relative of the misinformation effect that psychologists and legal 0:23:39.320 --> 0:23:44.160 theorists have studied, and this is the issue of cowitness contamination. 0:23:44.359 --> 0:23:47.159 The idea is that if you see a crime and 0:23:47.240 --> 0:23:49.639 I'm standing there and I see it too, and then 0:23:49.680 --> 0:23:52.960 we start talking with one another about it, we can't 0:23:53.000 --> 0:23:57.720 help but influence each other's memories. If you remember that 0:23:58.200 --> 0:24:00.800 she had curly hair, but I say I'm pretty sure 0:24:00.840 --> 0:24:04.520 she had straight hair. Or if you think she was unathletic, 0:24:04.600 --> 0:24:07.119 but I say, no, she was really athletic, each of 0:24:07.160 --> 0:24:11.480 our statements become part of each other's memory, and we 0:24:11.600 --> 0:24:16.080 more and more come to believe things that we didn't originally. 0:24:16.680 --> 0:24:19.480 And we see these kinds of memory problems all the time. 0:24:19.640 --> 0:24:23.880 In police lineups. For starters, it's really difficult to remember 0:24:24.359 --> 0:24:27.679 the face of a perpetrator in a crime scene. So 0:24:27.880 --> 0:24:32.200 police and researchers have tried every which way for people 0:24:32.240 --> 0:24:36.159 to have an easier time reconstructing a face. You maybe 0:24:36.200 --> 0:24:39.800 describe it to an artist, or you reassemble the face 0:24:39.840 --> 0:24:42.880 from a selection of different possible eyes and nose shapes 0:24:42.920 --> 0:24:45.840 and mouths, and in the last decades you can do 0:24:45.880 --> 0:24:48.880 this with three D avatars on a computer. But whatever 0:24:48.960 --> 0:24:53.160 tech is introduced, it doesn't matter. People's performance is terrible. 0:24:53.359 --> 0:24:58.879 Why because memories are not like photographs. So one issue 0:24:58.920 --> 0:25:02.600 that researchers started noticing and studying in the nineteen sixties 0:25:03.320 --> 0:25:08.399 was police suggestibility. So imagine you're shown a lineup with 0:25:08.480 --> 0:25:11.560 several people and you have to decide which person you 0:25:11.720 --> 0:25:15.680 saw doing the crime. But imagine that the police already 0:25:15.720 --> 0:25:19.200 have their man in mind. They already think that it's Steve. 0:25:19.359 --> 0:25:22.119 Whether or not that's correct, they believe it's Steve, and 0:25:22.160 --> 0:25:24.119 they want you to say it's Steve. There are all 0:25:24.280 --> 0:25:26.399 kinds of ways that they can suggest that to you, 0:25:26.600 --> 0:25:29.400 even if it's unconscious on their part. So for example, 0:25:29.880 --> 0:25:34.280 positive feedback. If you say I think that's the guy, 0:25:34.400 --> 0:25:37.280 they say, yeah, good job, that's what we think. Also, 0:25:37.800 --> 0:25:42.400 it turns out that the positive feedback influences the confidence 0:25:42.560 --> 0:25:46.240 of the eyewitness, and then when the trial starts months later, 0:25:46.400 --> 0:25:50.159 the eyewitness says, I'm absolutely certain that it was Steve, 0:25:50.400 --> 0:25:53.919 even though he doesn't remember that. He was not certain 0:25:54.000 --> 0:25:57.159 at all, but because of the positive feedback, which can 0:25:57.200 --> 0:26:01.159 even be quite subtle, his confidence goes way up. And 0:26:01.320 --> 0:26:05.280 decades of psychology studies in the laboratory have verified the 0:26:05.440 --> 0:26:08.280 power of this kind of suggestibility. The main thing that 0:26:08.640 --> 0:26:13.560