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Transcript Provided by YouTube:
00:00
It was midnight when Bernice got off work.
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She was exhausted after a long and terrible day, and just wanted to get home to a hot
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bath.
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She was driving down the street, flipping through radio stations, when she pulled up
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to a stop sign, and saw something weird.
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A shadowy figure ran up to an idling fruit truck, pushed the delivery man down, grabbed
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a crate of bananas, and ran off around the corner.
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Bernice was pretty shaken up, but she made sure the driver was okay, and then called
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the police, describing the thief as a pale, lanky man, wearing a dark jacket and a baseball
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cap.
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She gave the cops her information, and then she went home.
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A couple days later the police asked her to come down to the station to identify a potential
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thief–a guy who more or less matched her description, and was found eating a banana
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early that morning, near the scene of the crime.
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Although the guy professed innocence, Bernice said it was him, and they locked him up.
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But at the trial, the defense called a memory expert to the stand, and soon after that,
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the suspect walked.
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Today’s lesson may not quite make you an expert worthy of the witness stand, but by
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the time we’re done, you’ll understand a lot more about how we retrieve memories
00:58
we think we’ve stored, and why the accused banana thief was set free.
01:05
[INTRO]
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We’re all constantly retrieving memories throughout the day– you’re remembering
01:15
where you parked your car, or if you fed the cat, or called your mom ‘cause it’s her
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birthday.
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You’ll remember from last week that while our implicit memories–like how to talk and
01:23
ride a bike–are dealt with on a mostly automatic and non-conscious level, our explicit memories–the
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chronicles of our personal experiences and general knowledge — often require conscious,
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effortful work.
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Bernice had to notice, encode, store, and later consciously retrieve details about the
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crime she witnessed–what color was the guy’s jacket, what did he look like, what did he
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steal, and where did he run?
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It takes a lot of work to retrieve memories from long-term storage, and the truth is,
01:49
a lot can go wrong along the way.
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In order to understand all of the many fascinating ways you forget things, we need to talk more
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about how we remember.
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Our memories are not like books in the library of your mind.
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You don’t just pluck a neatly-packaged memory — about where you left your phone or the
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hair color of a fruit thief.
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Instead your memories are more like the spider webs in the dank catacombs of your mind–a
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series of interconnected associations that link all sorts of diverse things, as bits
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of information get stuck to other bits of information.
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Like, maybe Bernice remembers that the night of the crime was chilly with a full moon,
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and that Beyonce was on the radio, and the fruit truck had plates from California, which
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is where her grandfather lives.
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All those bits of information in the web of memory–the weather, the song, the plates–can
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serve as retrieval cues, kind of like a trail of breadcrumbs leading back to a particular
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memory.
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The more retrieval cues you inadvertently, or intentionally, build along the way, the
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better you can backtrack and find the memory you’re looking for.
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This way of activating associations non-consciously is called priming, sometimes called “memoryless
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memory”.
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It’s how “invisible memories” that you didn’t know you had can awaken old associations.
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Priming is how you often jog your memory.
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This kind of recall is sometimes referred to as context-dependent memory.
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Say you’re reading in bed, and you want to underline a quote, but you don’t have
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a pen.
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You get up and go into the other room to find your special light-up Hello Kitty pen, but
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you get distracted and suddenly you find yourself in the kitchen; you’re like “Why?
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Why, mind?
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Why am I in the kitchen?
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What is here?
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Why am- there was a rea- and I don’t know but I’m here now and agh!”
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It’s only when you retrace your steps and return to bed, to the initial context where
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you read that quote and encoded that first thought of wanting that pen, that the memory
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comes back.
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And then you’re like ‘oh, I need to go get the pen.
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Ugh’ If some memories are context-dependent, others
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are state-dependent, and also mood-congruent.
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This just means that our states and our emotions can also serve as retrieval cues.
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If I had a throbbing headache and a super bad day, I’m more likely to start recalling
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bad memories, because I’m priming negative associations.
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But of course if I’m relaxed and jolly, I’m prone to remember happy times, which
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are prolonging my good mood.
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Another funny memory-retrieval quirk speaks not to our location or emotions, but to the
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order in which we receive new information.
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So, say you make a grocery list in the morning, but a few hours later, you’re at the store,
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you realize you left it at home.
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You’d be more likely to recall the first items on the list–bananas and bread–and
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the last items–pickles and cheese–than anything in the middle.
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This is known as the serial position effect.
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This might be because the early words benefitted from what’s known as the primacy effect,
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and made it into your long-term memory because they were rehearsed more.
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Meanwhile, the last words lingered in the working memory through the recency effect.
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But those poor middle words, they didn’t benefit from either effect and therefore escaped
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your brain, which is why you now have no toilet paper, dog food, toothpaste, or cookies.
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Who forgets cookies?
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But even with all these tricks and associations, things still go wrong–memory can fail or
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become distorted, and of course we forget things.
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Forgetfulness can be as minor as those frustrating moments where you’re like ‘Ah, it’s
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on the tip of my tongue.
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It’s the guy, the guy’s got hair, and a face, and, like, shoulders.’
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Or as major as Clive Wearing, whose neurological damage made it impossible for him to recall
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the past or create new memories.
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Of course, we all forget things, and typically we do it in one of three different ways: We
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fail to encode it, we fail to retrieve it, or we experience what psychologists call storage
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decay.
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Sometimes forgetting something just means it never really got through your encoding
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process in the first place.
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I mean, think of all the stuff that’s going around you at any given moment.
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We only actually notice a fraction of what we sense, and we can only consciously hold
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so many bits of information in our minds at any given time, so what we fail to notice,
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we tend to not encode, and thus don’t remember.
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Bernice noticed a dark jacket, Beyonce, and bananas, but she didn’t encode much about
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the driver, or the color of the thief’s shoes.
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Then again, even memories that have been encoded are still vulnerable to storage decay, or
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natural forgetting over time.
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Interestingly, even though we can forget things pretty quickly, the amount of data that we
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forget can actually levels off after a while.
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This means that Bernice would have forgotten about half of what she first noticed from
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the crime scene a couple days later, but what she still remembered, she’d likely hang
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on to, because the rate at which we forget tends to plateau.
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A lot of times forgetting doesn’t mean our memory just faded to black, it means we can’t
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call it up on demand because of retrieval failure.
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We all know the common tip-of-the-tongue phenomenon where you feel like you know the name of that
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weird-looking hard-backed animal that rolls up into ball.
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It’s kind of cute and weird and I think they get leprosy or something…what is it?!
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This is where retrieval cues can come in handy.
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If I say is starts with the letter A, you may suddenly unlock the information–Armadillo!
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Sometimes these retrieval problems stem from interference from other memories getting in
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the way, essentially cluttering the brain.
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Sometimes, old stuff that you’ve learned keeps you from recalling new stuff — like,
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if you change one of your passwords, but keep recalling your old one every time you try
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to log in.
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That’s called proactive, or forward-acting, interference.
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The flip side is retroactive, or backward-acting, interference, which happens when new learning
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gets in the way of recalling old information, like if you start studying Spanish, it may
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interfere with the French that you’ve already learned.
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There’s a lot of reconstruction and inferring involved when you try to flesh out a memory,
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and every time you replay it in your mind, or relate it to a friend, it changes, just
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a little.
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So in a way, we’re all sort of perpetually re-writing our pasts.
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While this is an inevitable part of human nature, it can prove dangerous at times.
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Misleading information can get incorporated into a memory, and twist the truth – and yes
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there is an effect for this; it’s called the misinformation effect.
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American psychologist and memory expert Elizabeth Loftus has spent decades showing how eyewitnesses
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inadvertently tweak and reconstruct their memories after accidents or crimes.
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In one experiment, two groups watched a film of a car accident.
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Those asked how fast the cars were going when they smashed into each other estimated much
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higher speeds than those who were asked about the cars hitting each other.
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Smash is the leading word that essentially altered the witnesses’ memories — so much
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so that a week later, when both groups were asked if they saw any broken glass, those
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who heard the word smash were twice as likely to report seeing bits of glass, when in fact,
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the original film didn’t show any.
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In Bernice’s case, chances are her memory of the robbery would be altered if the prosecution
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said the thief assaulted, rather than pushed the driver.
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This sort of interfering or misleading information may also manifest itself as source misattribution,
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like when we forget or misrecall the source of a memory.
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In the case of Bernice, when she saw the suspect in the courtroom, she thought she recognized
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him from the night of the crime, when in reality, he’d just served her coffee earlier that
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day.
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But her memory of the event had probably already been tweaked several times before she even
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made it into the courtroom.
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Like she re-lived the tale multiple times, in her own mind or when she told other people
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about it, and every time she introduced errors, filling in memory gaps with reasonable guesses.
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Not only that, but we know Bernice was already tired and stressed when she witnessed the
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event, and we know our emotions can influence both what we remember and what we forget.
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Because memory is both a reconstruction and a reproduction of past events, we can’t
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ever really be sure if a memory is real just because it feels real.
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Elizabeth Loftus knows this.
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She’s frequently called in to testify against the accuracy of eyewitnesses.
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In fact, of all the U.S. prisoners who have been exonerated based on DNA evidence presented
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by Innocence Project, a non-profit legal group, 75 percent of them were convicted by mistaken
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eyewitnesses.
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That is a lot of innocent people.
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Bernice meant well of course, she’s an honest enough lady, but all these factors–the emotion,
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the retelling, the suggestions of outside sources– combined with the darkness, the
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quick glimpse, the passing of time, maybe even the Beyonce, ended up leading to a mistake
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in the thief’s identification.
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Turns out the human memory is actually a very fragile thing.
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We’re all largely the product of the stories that we tell ourselves.
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If you haven’t forgotten already, today you learned about how our memories are stored
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in webs of association, aided by retrieval cues and priming, and influenced by context
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and mood.
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You also learned how we forget information, how our memories are susceptible to interference
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and misinformation, and why eyewitnesses are often not as reliable as you might think.
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Thanks for watching, especially to all of our Subbable subscribers, who make this whole
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channel possible.
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To learn how you can keep these lessons coming while earning awesome perks, just go to subbable.com.
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This episode was written by Kathleen Yale, edited by Blake de Pastino, and our consultant
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is Dr. Ranjit Bhagwat.
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Our director and editor is Nicholas Jenkins, the script supervisor is Michael Aranda, who’s
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also our sound designer, and the graphics team is Thought Café.
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This post was previously published on YouTube.
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Photo credit: Screenshot from video.
