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Do you remember what you did a week before today? And are you sure you actually did that instead of dreaming it up? Our memory can be tricked easily. But how? Hank explains how your memories can be tricked.

Hosted by: Hank Green
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It’s easy to assume that your memory works like a camera.

You know how camera works, so it’s like how memories work. You take snapshots of your life, and sometimes it’s hard to find a picture, or you accidentally delete one.

But the ones you keep are a good record of what actually happened. But psychologists who study memory actually think it works more like a Wikipedia page. You can trust it as a general reference, but every time you remember something, you can make changes to it – and so can other people.

In fact, there are lots of ways your mind can be tricked into thinking things happened that never actually did. One way is through suggestion – basically, dropping hints that something happened a certain way. A psychology study in the mid-1970s was one of the first to show the power of verbal suggestions.

In one experiment, the researchers played college students videos of a car crash, and then asked some questions about the crash. One group was asked how fast they thought the cars were going when they hit each other. And another was asked how fast the cars were going when they smashed each other.

And that word choice affected their memory! When the researchers said “smashed” instead of “hit”, people's estimates of the speed increased by about 3 miles per hour. Then, when the psychologists followed up a week later, they asked if the participants remembered seeing broken glass in the video – which, for the record, there wasn’t.

Of the 50 people who heard the word "smashed," 16 remembered seeing broken glass that wasn’t actually there, as opposed to 7 of the 50 people who heard the word "hit.” Even without the suggestion, a few people were remembering incorrectly – but not as many. Now, that wasn’t a huge study, but the power of suggestion has been replicated hundreds of times in different experiments, so it seems like we’re pretty prone to getting little details wrong. Turns out, we’re also bad at remembering where we heard something in the first place, or whether something actually happened to us instead of, like, dreaming it up.

This is what’s known as source misattribution. In one study, psychologists tested for this effect by inviting some 210 volunteers into a lab for a couple days and asking them to either do or imagine doing a bunch of different things. There were familiar tasks, like smelling a flower, plus some weird ones, like tapping a flower to their forehead.

Then, two weeks later, they were asked to remember what they did. It didn't matter if it was something normal like rolling dice, or strange like sitting on dice– over half the time, participants thought they actually did the things that they only imagined. And if they spent more time imagining an action, they were more likely to think they really did it.

Now, both of these memory flaws have been psychologists sorta messing with people. But, sometimes, we just unintentionally make stuff up. These are called spontaneous false memories, this is when all the knowledge and patterns you have swimming around in your brain can mess up what you remember.

Let me show you. Try to remember this list of words. Think you have them all memorized?

Good. Now, take a look at these words. How many of them were on that first list?

In case you were wondering – and didn’t just write them down – the answer is six. But, in controlled lab experiments where they do have a little more time to memorize, most people will falsely remember one word that wasn’t on the first list: "window." That’s because the first list was basically a bunch of window-related words , so it’s easy for your mind to make a goof. This example is called a DRM List, named after the psychologists who wrote and studied it:.

Deese, Roediger, and McDermott. But spontaneous false memories can happen in all kinds of situations. For instance, one study showed children between 5 and 12 years old different versions of a video where a teacher read a story to a class, and then got money stolen from her wallet in a cafeteria.

Then, they had to pick the thief out of a lineup. In one version of the video, there was a bystander next to the teacher while she was reading – someone who was about the same age, build, gender, and ethnicity as the thief. And after watching that version, the 11 to 12 year-olds were more likely to pick the innocent person out of the lineup than the actual thief.

This is called unconscious transference: when an innocent person gets mis-remembered as a criminal because of the way your mind categorizes things like how they look. Psychologists think we make up these patterns as we go through life, most of the time without thinking about it. They’ve also noticed that adults usually show unconscious transference and mix up DRM lists more than really young children do, because they just have more life experience and general knowledge.

So… memory is kind of scarily unreliable. And it’s probably worth taking your own memory with a grain of salt. But now that you know some of the ways it can trick you, maybe you can avoid being /too/ trusting.

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