Introduction

The term explicit memory refers to knowledge you consciously know. You can think it in words or images, and state it out loud. In this chapter, we’ll  discuss different types of explicit memory, as well as some common ways in which these memories can be inaccurate.

Episodic and Semantic Memory

We divide episodic memory into a few different categories. One such category is episodic memory —your memory of events. This includes things like your memory of a social gathering you attended, a sporting event you participated in, or a show you watched. Most of these memories are going to have you in them, since you’re the one remembering them, but we sometimes refer to specific episodic memories that are about you as autobiographical memory.

Episodic memory is your memory of things that happen, but what about your memory of the facts and details that fill in those events? That is your semantic memory—your memory of things—facts, pieces of information, and concepts. One can actually represent your semantic memory as a web or network of concepts, connected by association…Surprise! We actually spent a large chunk of the first part of this book already discussing semantic memory, we just didn’t call it that.

While your memory of your sixteenth birthday party might be an episodic memory, your knowledge of your age and the name of the town you were in at the time are pieces of semantic memory. There can be overlap between the two; don’t worry too much about trying to draw a clear line between semantic and episodic memory. For now, let’s dig a little deeper into semantic memory. We already know a good way to represent how it’s organized in your brain. But how do we access it? What is it like to use it?

A really simple way to examine your semantic memory is to test your ability to memorize a list of words. For this exercise, you’ll need something to write on, and something to cover up the list once you’ve finished looking at it.

Got them? Good! Here are your instructions:

• Next, you’ll see a list of 20 random words, and your goal is to memorize them.
• Read them aloud, slowly, one at a time, once all the way through.
• Then, do it again!
• When you are done reading the list twice, cover them up, and count backwards from 10 to 0!
• Finally, write down as many words as you can recall.

Ready to go? Here is your list!

• Income
• Office
• Drawing
• Anxiety
• Medicine
• Studio
• Candidate
• Family
• Wife
• Growth
• Grocery
• Height
• Indication
• Contract
• Two
• Orange
• Hat
• Obligation
• Importance
• Drama

Congratulations! In the spirit of fairness, I did the exercise as well. Here’s what I came up with:

• Income
• Orange
• Hat
• Drama
• Obligation
• Science

I remembered 5 words from the list (and one that snuck in there that wasn’t on the list at all). Consider how you did! Specifically, consider the following questions:

• Did you remember income (the first word?)
• Did you remember drama (the last word?)

If you remembered the first or last word, you did something most humans do! In fact, you can graph the general pattern of how people tend to remember items from lists like this:

There are a few things going on here, and they’re all part of an umbrella of phenomena called serial position effects. First, we often remember the first word in a list. This is called the primacy effect. We also tend to remember things that just happened. This is called the recency effect. As for things in the middle of the list…they often get neglected.

Do our brains really care about beginnings and ends? Is it a meaningless artifact of how neurons work? There are many models out there that try to explain how or why these effects occur, but the important thing for us to know is that they happen consistently: all semantic memory is not equal! How you take in the information matters.

False Memories

Arguably, one of the most important things to know about semantic memories is that many of them are false! False memories are extremely common and a natural side-effect of how memories are formed, stored, and remembered.

The War of the Ghosts

In the early 1900s, a British psychologist named Frederic Bartlett performed a very influential experiment illuminating how memories change as they are stored in our brains. This study is known by the title of the story that Bartlett asked subjects to read and remember: The War of the Ghosts. Now, The War of the Ghosts is allegedly an Indigenous American story and the fact that it had a cultural context that was unfamiliar to the subjects of the experiment was important. However, I can find no evidence that it came from anywhere except Bartlett himself, so I’m a little concerned that it has nothing at all to do with any specific Indigenous people, and that Barlett just made it up. So, let’s set that aside and work through an example story that I generated using AI, with a few of my own tweaks. Don’t worry, it will serve the same purpose.

We’ll call this one The Man in the Mansion. Please read it now:

Perhaps it is not a classic of modern literature, but it should do for our purposes.

Now that you’ve been distracted for a few seconds, please recall every detail in the story that you can, to the best of your ability – as if you were telling it to a friend.

Done? Great! Here are some things that might be true regarding your recollection of the story:

• Your recollection is shorter than the original story
• Your recollection might not be 100% accurate
• Your recollection is unique to you

The Man in the Mansion was 305 words. Your recollection may or may not have been less than that, but odds are that even if you’re a particularly wordy person, you omitted a few details from the original. And that is by design.

Your brain is not a machine that makes copies of things. That is a good thing! It would be a huge waste of energy. Most of the time, we don’t need every detail of something. When you attend a baseball game, you don’t remember every single pitch; you just remember the exciting bits. When you see a movie, you remember the plot, and some specific things that stand out, but not every single second of the runtime.

Suppose you’ve saved a document on a computer. When you open the document, the words are exactly the same as they were when you left them—the computer saved the file with every detail intact. This is not what your brain does! When you “save” a memory in your brain, what is saved is a set of highlights, associations, and feelings. When you “re-open” the document to recall the memory, your brain brings up those flashes and fills in the rest on the spot.

In short, memory is what we call constructive. It does not mimic things; it creates them. The consequence of this is that every piece of information you’ve ever received from another human has a bit of them in it!

Creating False Memories

In the 2010 film Inception, the protagonists attempt to put ideas into the minds of others by travelling into their minds. The process is depicted as extremely risky and dangerous. However, “inception” is a lot easier in real life.

If a psychologist came up to you and told you that when you were six years old, you went on a hot air balloon ride with your family, would you believe them? Perhaps, but if you had no memory of this event, you likely won’t remember it. And you shouldn’t, because it never happened. The psychologist made it up.

But what if the psychologist had a picture of you and your family, there on the hot air balloon? What if they also reminded you of several stories that you do remember? What if you were asked to describe the memory to the best of your ability, repeatedly over several days?

Under those circumstances, people can sometimes generate false memories! Even if you never did go on a hot air balloon ride when you were six, you might come away from the interaction believing that you did.

This is a common format for a psychological experiment. In the table below, you can see several examples of psychology experiments that successfully convinced a portion of their subjects that they remembered something that in fact did not occur.

Experimenters convinced subjects…	By…	Citation
They took a kid on a hot air balloon ride	Showing them a doctored picture	Wade er al., 2002
They pranked a teacher	Telling them true stories alongside the fake story	Lindsay et al., 2004
They saw broken glass in a car crash scene	Asking them if they saw “the” broken glass	Loftus & Palmer, 1974
They spilled juice on someone at a wedding	Telling them true stories alongside the fake story	Hyman et al., 1995

All of these studies share a few important features. Many of these studies incorporated repetition. If you go up to someone and simply tell them “you went on a hot air balloon when you were six, don’t you remember?” it might not work. But if you go over the “memory” many times, over many different sessions, the person might start to form one.

Moreover, the studies above take advantage of subjects’ trust. Sometimes, they simply rely on the general faith people have in scientists, but often, they go even further. They provide subjects with falsified evidence of the event they are trying to convince them happened or hide the lie amongst truths and real details. Either way, it’s much easier to believe something when you assume the source is trustworthy and have legitimate evidence to back that up. In the following example, Dr. Gotcha fools Sunny by triggering real memories before probing for a false one and wearing his Science Goggles to appear more authoritative.

Can you imagine if I filled this textbook with lies? Don’t worry, I didn’t. But are you actually going to follow up on all my citations? What about everything I stated as fact but didn’t cite? Probably not —that would be a huge waste of time and defeat the point of the textbook. But if you don’t follow up on and fact-check every single thing I’ve said in this book, you’re taking a mental shortcut of sorts. You’re assuming that this is not a book of lies. Our brains are not wired to be constantly trying to catch lies. This makes life easier, but it also leaves our memories vulnerable.

Eyewitness Memory

Imagine you’re in a courtroom for a car mishap, and it matters whether you had been speeding or not. If someone asks a witness how fast they thought you were going, you’d hope their answer would be accurate. Now, we already know that memory isn’t always accurate, but what if on top of that, the way the lawyer asked the question actually influenced the witness’s answer?

In the 1970s, a psychologist named Elizabeth Loftus asked people to watch a video of a car accident. Afterwards, she asked them to tell her how fast they thought the car had been going. But there was a catch! Different subjects got slightly different worded questions. You can see the effect of these different words in Figure 6.3.

When deciding how fast the car was going when it contacted the mailbox, subjects reported its speed to be around 30 mph. When deciding how fast it was going when it smashed the mailbox, they reported its speed to be around 40 mph. The wording of the question alone was strong enough to influence the subjects’ memories! And we already know why—it’s because memory is constructive. When you think back to a thing you saw, you aren’t “replaying” it in your mind – you’re re-building it. And sometimes, irrelevant or noticeable information around you creeps into that reconstruction. If someone asks you to re-build a memory of a “smash,” you’re going to construct that memory with a little more intensity than you would if they asked you about a “contact.”