WEBVTT - Before You Could Remember, Part 2 0:00:02.960 --> 0:00:13.000 Welcome to Stuff to Blow Your Mind, the production of iHeartRadio. Hey, 0:00:13.039 --> 0:00:14.880 You're welcome to Stuff to Blow your Mind. My name 0:00:14.880 --> 0:00:17.959 is Robert Lamb, and I'm Joe McCormick, and we're back 0:00:18.000 --> 0:00:23.000 with part two of our series on childhood amnesia, which 0:00:23.079 --> 0:00:26.880 is the name for the fact that most adults and 0:00:27.000 --> 0:00:30.560 even most older children don't really seem to have any 0:00:30.640 --> 0:00:34.400 memories from before about the age of three or four. 0:00:34.520 --> 0:00:38.559 And that number is slightly different depending on the culture 0:00:38.600 --> 0:00:40.760 you grow up in and some other factors that we 0:00:40.800 --> 0:00:45.080 may continue to explore in this series, but generally, on average, 0:00:45.120 --> 0:00:48.360 around three or four is when the memories start kicking in, 0:00:48.800 --> 0:00:51.600 and even then people don't seem to have as many 0:00:51.720 --> 0:00:54.200 memories as they will for later years in life. That 0:00:54.280 --> 0:00:56.600 the number of memories people seem to be able to 0:00:56.600 --> 0:00:59.600 recall sort of goes up each year after that. More 0:00:59.680 --> 0:01:02.800 from You or five, more from six, More from seven. Now, 0:01:02.840 --> 0:01:04.759 if you haven't heard part one yet, you should probably 0:01:04.800 --> 0:01:07.319 go back and check that one out first. It is 0:01:07.360 --> 0:01:10.680 where it is where we learned that that Rob here 0:01:10.880 --> 0:01:14.200 was indeed once a very naughty boy and smashed a 0:01:14.319 --> 0:01:16.600 jar of cherries on the floor or something. What is 0:01:16.680 --> 0:01:18.920 it you do. Well. I mean, I guess the naughty 0:01:18.920 --> 0:01:21.080 part was going into the refridgerator to get them anyway, 0:01:21.080 --> 0:01:23.399 because I don't think I was supposed to have them. Yeah, 0:01:23.560 --> 0:01:26.600 were you explicitly forbidden cherries or I guess it's just 0:01:26.640 --> 0:01:28.720 a general understanding. If you're a child, you should not 0:01:28.800 --> 0:01:32.039 climb into the fridge to serve yourself anything. Well, you know, 0:01:32.120 --> 0:01:35.520 I don't know. I guess looking back on it. As 0:01:35.560 --> 0:01:37.720 a child, you're often sort of testing the boundaries of 0:01:37.760 --> 0:01:42.080 your world, and part of a memory like that is 0:01:42.080 --> 0:01:44.640 when you realize you're not supposed to Apparently I was 0:01:44.680 --> 0:01:46.400 not supposed to go back and get cherries for a 0:01:46.480 --> 0:01:49.840 number of reasons, some practical, uh, some maybe you know, 0:01:49.960 --> 0:01:54.400 arguable from from my standpoint. But yeah, that's that's kind 0:01:54.440 --> 0:01:55.920 of a There's a lot of stuff going on in 0:01:55.960 --> 0:01:58.640 those early years, which I think is something we tried 0:01:58.640 --> 0:02:02.480 to get across and all is that, Um, the brain 0:02:02.640 --> 0:02:06.280 of an infant or a small child is not inert. 0:02:06.480 --> 0:02:10.320 It is it is extremely busy, but the brain remembers 0:02:10.320 --> 0:02:13.120 what it needs to remember. And uh, and so we're 0:02:13.160 --> 0:02:15.240 going to continue with that in mind in this episode. 0:02:15.600 --> 0:02:18.320 That is a scary and kind of thrilling headspace to 0:02:18.320 --> 0:02:22.560 get back into the moment when you're like a child 0:02:22.600 --> 0:02:25.280 and you're doing something where you you really don't know 0:02:25.320 --> 0:02:27.320 if you are allowed to do this or not, and 0:02:27.400 --> 0:02:30.680 you suspect that you might not be, but you it's 0:02:30.680 --> 0:02:33.760 never been said outright, you know, or you just suspect 0:02:33.760 --> 0:02:36.760 that you are, you know. I mean, there's there's so 0:02:36.840 --> 0:02:39.120 much that that comes up in raising a child on 0:02:39.160 --> 0:02:41.120 this end where you're like, oh, yeah, I can't really 0:02:41.120 --> 0:02:43.840 be mad at him for thinking this or acting in 0:02:43.919 --> 0:02:48.400 this way because we've never said don't approach whatever the 0:02:48.440 --> 0:02:53.120 topic is this way. It's this is the learning experience. Yeah. 0:02:53.160 --> 0:02:56.280 So to start us off today, I just wanted to 0:02:56.280 --> 0:02:58.800 share something that I got to thinking about after the 0:02:58.880 --> 0:03:02.120 last episode. So this particular tangent is not something I 0:03:02.160 --> 0:03:04.680 have like direct scientific evidence for us, just something I 0:03:04.680 --> 0:03:07.720 started wondering about after the last part in the series. 0:03:07.840 --> 0:03:13.600 So I was thinking about childhood amnesia in the context 0:03:13.680 --> 0:03:17.560 of another subject we covered, I guess sometime last year 0:03:18.360 --> 0:03:20.880 it was the Hot Cold empathy Gap. Do you remember 0:03:20.919 --> 0:03:25.520 this episode, Rob, I do, Yes. This is an observed 0:03:25.560 --> 0:03:32.160 psychological phenomenon where we not only sometimes fail to understand 0:03:32.560 --> 0:03:37.400 accurately model and predict the thoughts and behaviors of other people. 0:03:37.480 --> 0:03:42.720 We not only have interpersonal failures of empathy, we also 0:03:42.880 --> 0:03:48.480 sometimes fail to accurately model ourselves in different affective states, 0:03:48.600 --> 0:03:52.800 so we have intra personal failures of empathy. So a 0:03:52.800 --> 0:03:54.839 simple way to put this is that people who are 0:03:54.960 --> 0:03:59.320 not currently in an affective state, so not currently angry 0:03:59.480 --> 0:04:04.440 or not currently hungry or not currently sad, are actually 0:04:04.520 --> 0:04:09.960 somewhat bad at at predicting how they themselves would react 0:04:10.040 --> 0:04:13.040 in a situation if they were actually in one of 0:04:13.080 --> 0:04:16.520 those states, and vice versa. If you are currently hungry, 0:04:17.040 --> 0:04:20.400 you're not very good at predicting how you would behave 0:04:20.400 --> 0:04:23.480 and react if you were not hungry. Yeah, like the 0:04:24.200 --> 0:04:27.200 fear area, for example. I mean it's it's easy to 0:04:27.240 --> 0:04:29.080 sort of rehearse what you're going to do in a 0:04:29.080 --> 0:04:33.000 certain situation, but then when the frightening thing occurs, you're 0:04:33.000 --> 0:04:35.280 in a different frame of mind and you may behave 0:04:35.400 --> 0:04:38.719 entirely differently. I reminded of there's a great scene in 0:04:38.760 --> 0:04:41.400 Congo with Ernie Hudson. Do you remember this scene where 0:04:41.480 --> 0:04:44.359 he's he's a very cool cucumber. His character the whole movie, 0:04:44.680 --> 0:04:48.080 there's a part where he's he's putting up a brave front, 0:04:48.080 --> 0:04:50.520 but then when the scary thing happens involving a gorilla 0:04:50.960 --> 0:04:53.760 like you, you turn back to him and he's he's 0:04:53.800 --> 0:04:56.039 a he's moved away, and or he's run away just 0:04:56.080 --> 0:04:57.960 a little bit, and asking what happened, he's like, I 0:04:58.040 --> 0:05:01.000 ran away. Yeah. He had just given a speech about 0:05:01.000 --> 0:05:03.320 how you can't run away because that will show Yeah, 0:05:03.360 --> 0:05:05.840 then the gorilla will chase you, so you can't stand 0:05:05.839 --> 0:05:10.520 your ground. But then I run away. Yes. So when 0:05:10.520 --> 0:05:13.719 we're not in these affective states, we actually can't relate 0:05:13.920 --> 0:05:16.200 very well to the person we are when we're in them, 0:05:16.240 --> 0:05:18.600 and vice versa. When we're in them, we can't really 0:05:18.600 --> 0:05:20.600 relate very well to the person we are when we're 0:05:20.640 --> 0:05:24.080 not in them. And so the hot cold empathy gap 0:05:24.120 --> 0:05:27.359 can be demonstrated over a span of only a few minutes. 0:05:27.440 --> 0:05:32.719 But it got me thinking about a similar self reflective 0:05:32.720 --> 0:05:37.400 empathy gap that applies not across different affective states, but 0:05:37.520 --> 0:05:40.920 different stages of life. So what I'm talking about here 0:05:41.720 --> 0:05:46.080 is when I think back on a memory of doing 0:05:46.160 --> 0:05:50.400 something or saying something, or dressing a certain way or 0:05:50.560 --> 0:05:54.799 liking a certain thing, When I was young, and especially 0:05:54.839 --> 0:05:57.719 if I pick something embarrassing, but not just with embarrassing things, 0:05:57.720 --> 0:06:02.000 with all kinds of things, I can often find myself 0:06:02.240 --> 0:06:07.320 totally unable to relate to that person. I say that 0:06:07.400 --> 0:06:10.679 thing that you've probably heard people say of similar similar 0:06:10.680 --> 0:06:14.760 reactions to their own past. What was I thinking? And 0:06:14.880 --> 0:06:17.960 at least when I say this, I truly often do 0:06:18.040 --> 0:06:23.040 not know. It's like I cannot internally simulate the mindset 0:06:23.120 --> 0:06:25.680 that led me to wear that T shirt, even though 0:06:25.720 --> 0:06:28.920 it was me. I can't relate to that person, and 0:06:29.000 --> 0:06:32.200 I can't even really remember or imagine what it was 0:06:32.240 --> 0:06:34.719 like to be them, even though again it was me. 0:06:35.720 --> 0:06:38.320 From what I gathered, this is a common experience. It's 0:06:38.360 --> 0:06:41.240 it's I'm not alone here, right Oh yeah, yeah, I 0:06:41.240 --> 0:06:43.520 mean it's like basically comes down to the reality that 0:06:43.560 --> 0:06:49.000 we are not consistently the same across a small lengths 0:06:49.000 --> 0:06:51.880 of time, much less across the course of a lifetime. 0:06:52.440 --> 0:06:54.760 And yeah, I mean it's it's a you know, a 0:06:54.760 --> 0:06:58.400 turn of phrase, what was I thinking? Sometimes we can 0:06:58.480 --> 0:07:00.440 piece together some of what our thought press us as 0:07:00.440 --> 0:07:02.480 were you know, you'd be like, well, I was a 0:07:02.520 --> 0:07:04.800 teenager and I thought this band was cool, so of 0:07:04.800 --> 0:07:07.160 course I wore that T shirt even if I would 0:07:07.200 --> 0:07:10.200 not be into that band. And now as as as 0:07:10.240 --> 0:07:12.240 a grown person or what have you, or with you know, 0:07:12.800 --> 0:07:15.520 you know, it's a certain amount of of clarity based 0:07:15.560 --> 0:07:18.560 on where you are now in life. But other times, yeah, 0:07:18.600 --> 0:07:20.240 you may genuinely look back and you're like, I just 0:07:20.280 --> 0:07:22.280 don't know what was going through my mind. I'm not 0:07:22.320 --> 0:07:25.360 sure what the thought process was. I seem to have 0:07:25.400 --> 0:07:28.080 a different thought process going on now. Yeah, And so 0:07:28.120 --> 0:07:32.160 obviously it's not this way with all memories from different 0:07:32.200 --> 0:07:34.960 stages of life. Like I have a feeling that I 0:07:35.000 --> 0:07:38.840 can re experience or relate to lots of memories from 0:07:38.920 --> 0:07:43.120 childhood but not other ones, And so I don't always 0:07:43.120 --> 0:07:46.000 know what makes the difference. But I wonder if the 0:07:46.320 --> 0:07:51.480 proportion of memories for behaviors and experiences we can no 0:07:51.720 --> 0:07:56.720 longer empathize with tends to increase the farther back you 0:07:56.760 --> 0:07:59.040 go into childhood. I don't know this is the case. 0:07:59.080 --> 0:08:02.320 I'm wondering if it does, or if say it actually 0:08:02.320 --> 0:08:04.480 doesn't go up in a linear fashion. You could imagine 0:08:04.520 --> 0:08:07.720 it also like pequing in teenage years or something like that. 0:08:08.920 --> 0:08:11.160 But so that's one question I was wondering about, and 0:08:11.200 --> 0:08:13.520 then I was also wondering if there's any kind of 0:08:13.560 --> 0:08:19.640 relationship between our current ability to empathize with our feelings 0:08:19.680 --> 0:08:23.440 and behavior in a past event and our tendency to 0:08:23.600 --> 0:08:27.440 actually remember that event in the first place. So, in 0:08:27.480 --> 0:08:30.800 other words, are we more likely to remember doing or 0:08:30.840 --> 0:08:33.800 feeling or saying something when we can empathize with it, 0:08:33.840 --> 0:08:35.880 like when we can get back in that mind space, 0:08:36.160 --> 0:08:39.000 and less likely to remember it when we can no 0:08:39.080 --> 0:08:44.320 longer empathize with it. And I asked this specifically because Rob, 0:08:44.480 --> 0:08:46.520 I wonder if you have the same experience. I feel 0:08:46.520 --> 0:08:50.200 like a lot of these what was I thinking memories 0:08:50.559 --> 0:08:55.960 are prompted by external intrusions, like seeing a photo of 0:08:56.000 --> 0:09:00.120 yourself that you didn't expect to see, or having somebody say, hey, 0:09:00.120 --> 0:09:02.360 do you remember when we did this or when you 0:09:02.400 --> 0:09:05.280 said that yeah, yeah, And it does make me I 0:09:05.320 --> 0:09:08.440 was thinking about this in terms of like childhood versus say, 0:09:08.520 --> 0:09:11.319 like junior high teen years sort of reflections, or even 0:09:11.360 --> 0:09:13.960 like early or really all of one's twenties. I guess, 0:09:14.960 --> 0:09:16.720 depending on where you are in life, how from fire 0:09:16.720 --> 0:09:20.160 removed you are from particular time period. But like for 0:09:20.280 --> 0:09:22.720 very young children, it seems like so much of what 0:09:22.760 --> 0:09:26.640 you end up doing and wearing, etc. Is almost entirely 0:09:26.640 --> 0:09:30.360 shaped by your parents anyway. Yeah, yeah, so like what 0:09:30.400 --> 0:09:32.319 was I thinking is not really a question because it's 0:09:32.320 --> 0:09:35.560 like you weren't thinking, you were just doing or you 0:09:35.559 --> 0:09:38.640 were just you wore this because it was provided to 0:09:38.760 --> 0:09:40.920 you and everyone else in your family liked it, so 0:09:40.920 --> 0:09:42.520 it seemed like you liked it. That sort of thing. 0:09:42.840 --> 0:09:44.920 Not all the time, but like I feel like maybe 0:09:44.920 --> 0:09:46.679 like eighty percent of the time that is something that 0:09:47.040 --> 0:09:49.160 may be the case. But then it's when you're getting 0:09:49.200 --> 0:09:52.240 into that area where you are willfully setting out on 0:09:52.280 --> 0:09:56.840 your own, choosing things for yourself, that might be the 0:09:56.880 --> 0:10:00.520 area where I mean, you're you're legitimately asking what was thinking? 0:10:00.600 --> 0:10:02.920 What was my intention in all of that? That is 0:10:02.920 --> 0:10:06.360 a good point, like what role agency or self control 0:10:06.440 --> 0:10:10.319 has in the event that you're remembering? So yeah, I 0:10:10.640 --> 0:10:14.040 don't know if our empathy gap with our past self 0:10:14.080 --> 0:10:17.400 actually does just increase the farther back you go. I 0:10:17.440 --> 0:10:20.439 wonder if that could be measured. But if it does, 0:10:20.559 --> 0:10:23.600 I wonder how does that also relate to the relative 0:10:23.640 --> 0:10:27.480 paucity of memories from early childhood and the foremost people 0:10:27.880 --> 0:10:32.520 complete lack of memories from four ages three or four. Yeah, Now, 0:10:32.600 --> 0:10:36.559 I this is interesting to think about. And one possible 0:10:37.000 --> 0:10:39.880 answer to this might be, well, the reason that you 0:10:40.000 --> 0:10:43.640 have trouble knowing or understand what you were thinking about 0:10:43.679 --> 0:10:47.439 in a particular time might be because you have completely 0:10:47.440 --> 0:10:50.920 blocked it out because their thought process was so traumatic 0:10:52.360 --> 0:10:55.840 that you just had to erase it from like easy 0:10:55.880 --> 0:10:59.600 access of the conscious mind. Ah, speaking of what we're rethinking, 0:11:00.640 --> 0:11:04.440 I guess, as with many topics in psychology, unfortunately, if 0:11:04.440 --> 0:11:07.600 you want to trace the history of how we understood 0:11:07.600 --> 0:11:09.520 this over the past one hundred years, you really you 0:11:09.559 --> 0:11:12.840 have to go back to Freud. Not because the Freudian 0:11:12.920 --> 0:11:18.280 explanations carry any scientific currency today they almost never do. Instead, 0:11:18.280 --> 0:11:21.839 it's just because you got to understand how influential Freudian 0:11:21.880 --> 0:11:25.000 theories were in the history of how people thought about 0:11:25.040 --> 0:11:27.920 this exactly. Yeah, yeah, and of course, yeah, we're talking 0:11:27.920 --> 0:11:32.600 about Sigmund Freud here, Austrian neurologist and founder of psychoanalysis, 0:11:33.160 --> 0:11:37.360 and he too explored the topic of quote unquote infantile amnesia, 0:11:37.880 --> 0:11:43.520 postulating that these lost memories constitute repressed memories repressed due 0:11:43.520 --> 0:11:47.800 to their psycho sexual nature. Here's a quote from Freud 0:11:47.920 --> 0:11:51.880 Obviously in translation quote, I believe that the infantile amnesia, 0:11:52.000 --> 0:11:55.480 which causes the individual to look upon his childhood as 0:11:55.480 --> 0:11:59.040 if it were a prehistoric time and conceals from him 0:11:59.080 --> 0:12:02.959 the beginning of his own sexual life. That this amnesia 0:12:03.120 --> 0:12:06.080 is responsible for the fact that one does not usually 0:12:06.120 --> 0:12:10.000 attribute any value to the infantile period in the development 0:12:10.240 --> 0:12:13.520 of the sexual life. Right. So, I think the common 0:12:13.600 --> 0:12:18.280 understanding of the Freudian view is that early childhood is 0:12:18.320 --> 0:12:23.760 a time of strange sexual fixations and realizations that we 0:12:24.320 --> 0:12:28.199 can't bear to think back about as adults, so we 0:12:28.280 --> 0:12:31.920 repress those memories as a type of trauma. I don't 0:12:31.920 --> 0:12:35.719 think there's any good empirical evidence for the Freudian psychosexual 0:12:35.960 --> 0:12:39.680 view of development today. Yeah. Yeah, It frankly doesn't gel 0:12:39.760 --> 0:12:42.200 with any of the science we've we've looked at in 0:12:42.240 --> 0:12:45.320 our research for these episodes, and it's mainly worth mentioning 0:12:45.320 --> 0:12:47.120 because of its place in the history of the topic 0:12:48.080 --> 0:12:51.959 and so forth. But it's also it's interesting to think about, 0:12:52.000 --> 0:12:56.280 like what's going on with this approach to infantile amnesia, 0:12:56.360 --> 0:13:00.800 to the seeming lack of real, congrete memories of early life, 0:13:01.000 --> 0:13:03.080 because you can think of them as sort of like 0:13:03.160 --> 0:13:07.200 blank spots upon which you can you can focus ideas 0:13:07.280 --> 0:13:11.199 like this, There's there's no possible memory there to contradict 0:13:11.280 --> 0:13:14.320 the backward looking explanation. You know. Well, Yet not only 0:13:14.400 --> 0:13:16.640 because it's a blank spot you can fill in with 0:13:16.679 --> 0:13:20.720 your explanations, but because of the particular characteristics of memory 0:13:21.320 --> 0:13:25.959 as a function of human brains, it's also actually not 0:13:26.120 --> 0:13:30.880 only possible, but quite trivial to place memories. There are 0:13:30.960 --> 0:13:33.840 things that feel like memories that do not reflect events 0:13:33.880 --> 0:13:36.320 that actually happened. Yeah, it brings to mind that the 0:13:36.400 --> 0:13:40.160 use of so called repressed memories not only in psychotherapy, 0:13:40.200 --> 0:13:43.320 but in the pursuit of paranormal experiences as well, such 0:13:43.360 --> 0:13:48.719 as alien abductions and ritual satanic abuse. Right, And this 0:13:48.760 --> 0:13:51.960 is a really dangerous area because, for one thing, I 0:13:52.000 --> 0:13:56.120 think it's important to acknowledge that it's impossible to rule 0:13:56.280 --> 0:14:01.520 out the idea that repressed memories exist. Right. It is 0:14:01.720 --> 0:14:06.760 possible that the brain somehow does retain memories that are 0:14:06.840 --> 0:14:11.720 not easily retrieved with you know, just regular conscious effort, 0:14:11.760 --> 0:14:14.920 but that could be retrieved by some other method. But 0:14:15.240 --> 0:14:19.200 while it's possible, one thing that research makes very clear 0:14:19.800 --> 0:14:24.119 is that it is incredibly easy to mistake false recovered 0:14:24.160 --> 0:14:29.680 memories for real ones, and the false memories feel completely convincing, 0:14:29.800 --> 0:14:32.600 just as real as actual memories. In fact, they are 0:14:32.640 --> 0:14:35.720 often even stronger and more vivid than real memories. And 0:14:35.760 --> 0:14:38.720 you can show this with experiments where you know, people 0:14:38.720 --> 0:14:41.760 will say, like, we consulted with your family and they 0:14:42.880 --> 0:14:45.320 they told us a story about a time, you know, 0:14:45.360 --> 0:14:47.680 that you got lost at the playground, but then you 0:14:47.720 --> 0:14:51.120 met this person and whatever, and this will be completely 0:14:51.160 --> 0:14:53.800 made up for the purpose of the experiment, but many 0:14:53.920 --> 0:14:56.960 people will start to believe that is a real memory 0:14:57.000 --> 0:15:00.960 they have in their head. Just vividly imagine a scenario 0:15:01.160 --> 0:15:04.800 proposed by someone else is often enough to make someone 0:15:04.880 --> 0:15:08.560 totally convinced of it as a memory. Yeah, then these 0:15:09.200 --> 0:15:11.920 alien abductions and ritual satanic abuses are both the topics 0:15:11.920 --> 0:15:15.160 we've discussed on the show before. But like very briefly, 0:15:15.320 --> 0:15:18.600 like just the the the idea is so heartbreaking that 0:15:18.680 --> 0:15:24.680 you could be manipulated into creating a memory of trauma 0:15:24.800 --> 0:15:27.840 and the memory would be traumatic like like once it 0:15:27.880 --> 0:15:31.960 has been sort of created and or augmented in your memory, 0:15:32.360 --> 0:15:34.560 like it's um you know, it's it's a thing that 0:15:34.680 --> 0:15:39.000 is that is real to you. So yeah, but heartbreaking 0:15:39.080 --> 0:15:41.040 is it as it is? It also just drives home 0:15:41.120 --> 0:15:44.160 something that is possible in all of our memories and 0:15:44.200 --> 0:15:46.840 really is going on at a less traumatic level with 0:15:46.960 --> 0:15:50.640 so many everyday memories in our lives. Yes, and while 0:15:50.640 --> 0:15:53.040 I would also point out that it seems especially easy 0:15:53.080 --> 0:15:55.520 to do this with the idea of early childhood memories, 0:15:55.560 --> 0:15:58.880 this also works for adults, like you can you can 0:15:58.960 --> 0:16:02.080 get adults to remember events that did not take place 0:16:02.200 --> 0:16:06.000 by by causing them to vividly imagine the event or 0:16:06.080 --> 0:16:18.960 something like that. All right, well, we'll getting away from 0:16:19.000 --> 0:16:23.240 from even the idea of alien abductions. Let's get back 0:16:23.280 --> 0:16:28.120 into what the actual research seems to illuminate about this topic. Well, 0:16:28.160 --> 0:16:29.600 one thing I think we should say at the beginning 0:16:29.720 --> 0:16:33.040 is that it's still somewhat an open question why childhood 0:16:33.040 --> 0:16:37.280 amnesia occurs, and there are competing theories that might that 0:16:37.320 --> 0:16:40.080 are to some degree competing, but they might also be complementary. 0:16:40.120 --> 0:16:43.760 There might be multiple factors contributing to this overall pattern 0:16:44.280 --> 0:16:48.800 where most adults can not really remember much of anything 0:16:48.840 --> 0:16:51.400 from before age about three or four, and then have 0:16:51.520 --> 0:16:56.120 this gradual accumulation of more memories to about seven or eight. 0:16:56.600 --> 0:16:59.680 We'll probably explore some hypotheses in this part and then 0:16:59.760 --> 0:17:02.040 more or in the next part in this series, But 0:17:02.080 --> 0:17:05.359 there was one I wanted to talk about because it 0:17:05.480 --> 0:17:10.879 seems like a pretty straightforward explanation based on neural development, 0:17:10.920 --> 0:17:14.399 the development of regions of the brain, especially a region 0:17:14.480 --> 0:17:17.760 known as the hippocampus. And so this was in a 0:17:17.800 --> 0:17:21.960 paper I was reading by Christina m. Alberini and Alessio 0:17:22.040 --> 0:17:26.040 Travaglia published in the Journal of Neuroscience in twenty seventeen 0:17:26.359 --> 0:17:30.400 called infantile amnesia a critical period of learning to learn 0:17:30.520 --> 0:17:34.840 and remember. And this paper highlights a seeming paradox. So 0:17:34.920 --> 0:17:37.280 on one hand, there's this phenomenon we've talked about at 0:17:37.359 --> 0:17:41.960 length now, early experiences seem to be forgotten very rapidly, 0:17:42.600 --> 0:17:48.240 and yet simultaneously, early experiences seem to be incredibly influential 0:17:48.440 --> 0:17:53.399 on adult behavior and adult brain development, to the extent 0:17:53.480 --> 0:17:56.640 that early childhood experience is a very well documented risk 0:17:56.720 --> 0:18:02.080 factor for various adult psychopathologies and disorders. Just to cite 0:18:02.160 --> 0:18:06.800 one example, there is extensive evidence that neglect during early 0:18:06.880 --> 0:18:11.560 childhood development can lead to disorders, including depression and anxiety, 0:18:11.760 --> 0:18:15.520 as well as learning and cognitive disabilities in later life. 0:18:15.920 --> 0:18:19.439 And there are similar findings about childhood poverty leading to 0:18:19.560 --> 0:18:22.639 cognitive and learning deficits that persist into later life. A 0:18:22.680 --> 0:18:25.359 lot of these effects are thought to be at least 0:18:25.359 --> 0:18:29.040 in part related to chronic stress in early childhood, though 0:18:29.040 --> 0:18:32.320 the authors of this paper proposed that it might not 0:18:32.480 --> 0:18:35.400 just be the effects of stress leading to these outcomes, 0:18:35.400 --> 0:18:39.560 but also the absence of what they call quote enrichment 0:18:39.800 --> 0:18:45.880 in episodic or declarative experiences in early development. So we 0:18:46.000 --> 0:18:50.320 know that early childhood experiences have this profound impact on 0:18:51.200 --> 0:18:55.120 how your brain works later in life, and yet much 0:18:55.200 --> 0:18:58.320 of what we learn in this period cannot be recalled 0:18:58.440 --> 0:19:02.840 later in narrative or episodic form. So the authors say, quote, 0:19:03.080 --> 0:19:06.639 how then can memories that are rapidly forgotten and of 0:19:06.680 --> 0:19:10.359 which there is virtually no recollection in adulthood exert a 0:19:10.520 --> 0:19:14.960 lifelong effect on the brain and cognitive function. And the 0:19:15.040 --> 0:19:18.960 answer that the authors of this paper propose lies in 0:19:19.240 --> 0:19:24.720 the hippocampus. So the hippocampus is crucial for the formation 0:19:24.880 --> 0:19:28.399 and maintenance of episodic memories. It's thought to be necessary 0:19:28.440 --> 0:19:31.840 for certain kinds of learning for the encoding of long 0:19:31.920 --> 0:19:35.600 term memory and related brain functions like spatial memory and 0:19:35.720 --> 0:19:39.560 navigation of spaces. And an interesting fact is that this 0:19:39.600 --> 0:19:41.680 is not true just of humans, but it's true of 0:19:41.760 --> 0:19:45.399 humans and non human mammals. The hippocampus is part of 0:19:45.440 --> 0:19:48.600 the limbic system, so it is part of the brain 0:19:48.640 --> 0:19:52.800 that we share with other mammals, and the author is 0:19:52.960 --> 0:19:55.679 right that in both humans and non human mammals. But 0:19:55.720 --> 0:20:00.480 they call wwww memories, which I guess is more of 0:20:00.480 --> 0:20:02.320 a shorthand when you type it than you say it 0:20:02.359 --> 0:20:05.840 out loud. But that stands for who, what, when, and 0:20:05.920 --> 0:20:10.280 where memories. So these are explicit memories that require conscious recollections. 0:20:10.480 --> 0:20:13.280 That this would have some overlap with the idea of 0:20:13.280 --> 0:20:16.359 like episodic memories, memories of like events that happened that 0:20:16.440 --> 0:20:19.280 you can recall in detail. The authors say that these 0:20:19.320 --> 0:20:24.200 memories are processed by the hippocampus dependent learning and memory system, 0:20:24.240 --> 0:20:27.600 also known as the medial temporal lobe dependent learning and 0:20:27.720 --> 0:20:32.000 memory system. So based on comparing what we know about 0:20:32.119 --> 0:20:36.400 hippocampal development in humans with the results of studies based 0:20:36.520 --> 0:20:41.840 on learning in early development in rats, the authors actually 0:20:41.920 --> 0:20:46.960 argue that quote, the hippocampal memory system, like sensory functions 0:20:47.000 --> 0:20:52.200 and language matures through experience and undergoes what they call 0:20:52.280 --> 0:20:56.640 a developmental critical period. Now, they deal with a couple 0:20:56.680 --> 0:21:00.359 of pre existing hypotheses about what's going on here. They 0:21:00.400 --> 0:21:05.720 identify as the developmental hypothesis, which basically says that these 0:21:05.880 --> 0:21:10.160 wwww memories, they are not stored in the long term 0:21:10.240 --> 0:21:15.640 quote because the hippocampus is immature and therefore unable to process, consolidate, 0:21:15.680 --> 0:21:20.120 and store contextual and episodic representation. So it's just functionally 0:21:20.280 --> 0:21:23.439 not competent to do this yet. And then on the 0:21:23.480 --> 0:21:27.520 other hand, there's this hypothesis known as the retrieval hypothesis, 0:21:27.560 --> 0:21:31.240 which quote posits that infantile memories are not gone, but 0:21:31.320 --> 0:21:34.760 are instead stored in some form that cannot be expressed 0:21:35.160 --> 0:21:40.040 due to retrieval failure, and they essentially thread the needle. 0:21:40.080 --> 0:21:43.560 They argue that both of these kind of get something right, 0:21:43.640 --> 0:21:46.919 but neither one is exactly right, and instead they end 0:21:47.000 --> 0:21:50.840 up arguing that the hippocampus and the hipocampal learning system 0:21:51.400 --> 0:21:55.600 are very active in early childhood and they are very 0:21:55.680 --> 0:22:01.879 much processing experiences during this early developmental period. But instead 0:22:02.040 --> 0:22:05.680 of storing memories exactly the same way it will once 0:22:05.720 --> 0:22:09.760 it is a mature organ it is learning how to learn. 0:22:11.520 --> 0:22:13.439 I also have to mention here, though, that it is 0:22:13.480 --> 0:22:17.960 interesting that the developmental hypothesis and the retrieval hypothesis, both 0:22:17.960 --> 0:22:22.920 of these in their own way reflect different former ideas 0:22:23.000 --> 0:22:26.920 about the minds of young children. Developmental being well, like, 0:22:26.960 --> 0:22:29.160 that's not a full blown human yet, of course, it's 0:22:29.200 --> 0:22:31.600 not gonna think the way we think or remember the 0:22:31.640 --> 0:22:34.600 way we think. And in the retrieval hypothesis, it's kind 0:22:34.600 --> 0:22:37.359 of in some you know, it's not exactly like Freud, 0:22:37.400 --> 0:22:39.160 but you know, it gets into that similar area, like, oh, 0:22:39.280 --> 0:22:41.320 those memories are there, They're just not in a way 0:22:41.320 --> 0:22:43.320 in there in a place that we can easily get 0:22:43.359 --> 0:22:46.160 to them, right. And I think these authors think that 0:22:46.200 --> 0:22:49.520 there is an element of truth to both of these views, 0:22:49.520 --> 0:22:53.040 but that neither one is exactly correct. That instead, it's 0:22:53.480 --> 0:22:58.360 that the hippocampus is working really hard to process experiences 0:22:58.440 --> 0:23:00.760 during this time, but the main thing it's doing with 0:23:00.760 --> 0:23:05.280 those experiences is learning how to learn. So the hippocampus 0:23:05.440 --> 0:23:09.480 does store memories, which can be maintained, they say, through 0:23:09.560 --> 0:23:13.399 frequent recalls, but they say without some form of ongoing 0:23:13.440 --> 0:23:18.280 recall or subsequent activation or modulation, those memories can tend 0:23:18.359 --> 0:23:21.679 to decay rather quickly. And so they say, quote the 0:23:21.720 --> 0:23:25.600 types of experience to which an individual is exposed during 0:23:25.680 --> 0:23:29.959 development shape learning abilities an important implication that highlights the 0:23:30.000 --> 0:23:34.640 fundamental roles of developmental environments. So this period is very important, 0:23:34.640 --> 0:23:37.480 and it does change the brain in a way that 0:23:37.520 --> 0:23:40.560 will affect the person throughout the rest of their life. 0:23:41.480 --> 0:23:44.800 But a lot of that, they argue, is through affecting 0:23:44.880 --> 0:23:48.399 how the hippocampus develops and thus how the brain learns 0:23:48.480 --> 0:23:51.280 to learn. And I'm not going to go into great 0:23:51.320 --> 0:23:55.840 granular detail on what the mechanisms are within this, but 0:23:56.000 --> 0:24:00.480 basically they propose a process by which there's sort of 0:24:00.480 --> 0:24:04.920 a sequence of different stages of development within critical periods 0:24:05.040 --> 0:24:07.480 for development in the brain. And this is true of 0:24:07.760 --> 0:24:11.919 not just learning and memory. It's true of like sensory functions, 0:24:11.920 --> 0:24:15.359 like certain sensory things come online and the development of 0:24:15.400 --> 0:24:18.840