How Our Memory Makes Mistakes—and How We Can Improve It

Memory is a funny thing. Most of us have plenty of memories (plural), both good and bad, those we wish we could remember better and in more detail—and those memories we wish we could forget, or at least ask them to stop popping unwanted into our head.

Our memories can be crystal clear about some events, hazy with others. Other memories are lost forever. Our memory may even seem like it’s playing tricks on us, when we can’t recall the details of a conversation, a person’s face or where in the world we put our car keys.

BrainWise recently interviewed memory expert Daniel L. Schacter, PhD, about how memory works—and doesn’t work—and what he has learned about how memory can enhance our imagination about the future and even boost our creativity.

“Our research challenges the notion that memory is only about the past—or that memory is like a tape recorder. Memory is a much more dynamic, constructive process than many people may think,” Dr. Schacter said.

Dr. Schacter is the William R. Kenan Jr. Professor of Psychology at Harvard University. He is the author of the books “Searching for Memory” and “The Seven Sins of Memory” and co-author of the introductory text “Psychology.” Dr. Schacter’s research has explored the relation between explicit and implicit forms of memory, the nature of memory distortions, how individuals use memory to imagine future events, the relation between creative thinking and remembering, and the effects of aging on memory.

Dr. Schacter will be a keynote speaker at this year’s annual conference of the National Academy of Neuropsychology—which produces BrainWise. His presentation will be “Creativity, Imagination and Memory: A Cognitive Neuroscience Approach.”

This Q&A has been edited for length and clarity.

BrainWise: Let’s start with a short, but possibly very big question: What is memory?

Daniel L. Schacter, PhD: The traditional definition of memory is a capacity of the mind that has three primary components: encoding, storage and retrieval. Encoding refers to how we initially process information, how we get it into the memory system. How we think about information when we encode it has a huge impact on the likelihood that we’ll later remember or forget that information.

Next, the storage stage. The idea here is that if we encode an experience or fact, information has to be retained over time. Fortunately, memory has a large storage capacity.

Finally, retrieval is the last stage. We can encode something, and it can persist over time in storage, but it’s not of very much use to us unless we can retrieve that information in some manner.

What is the purpose of memory?

There’s probably not just one. Certainly preserving information about past experiences is a critical function of memory. We know what happens when there’s damage to the brain that prevents people from retaining information over time. If they have a significant memory disorder, it has a big impact on everyday life.

What we’ve been focusing on in my research is the idea that memory is not just about the past or a capacity that allows us to reflect on our past experiences. That’s certainly a big part of it, but it also allows us to use our past experiences to think about the future—to imagine, based on past experiences, how future experiences will play out.

Memory is a multi-faceted function, something that allows us to preserve information over time, allows us to revisit the past, and also allows us to look forward into the future and to plan and problem-solve based on our past experiences.

You first wrote your book “The Seven Sins of Memory” in 2001 and updated it in 2021. What are these seven aspects of memory—and why call them “sins”?

I first proposed the seven sins idea about 25 years ago, when I was surveying [the research] on memory errors—forgetting and distortion in memory. The conclusion I came to was that there were these seven basic categories of memory error, so I called them “sins” as an analogy with the seven ancient deadly sins. Three are sins of omission, which have to do with different kinds of forgetting. Then we get into the sins of commission, in which memory is present but either wrong or unwanted. (See sidebar below to read about the seven sins of memory in detail.)

Why are there so many problems with memory, and is our memory out to trick us?

It’s a good question. I don’t think memory is trying to fool us or trick us. It’s just that the way that memory works—and generally does a good job for us—ends up feeling like we’re being tricked by memory. Let’s take the memory “sin” of misattribution. Misattribution occurs when we remember some aspect of an event correctly but we get the source wrong. An example of this that I used when I first wrote “The Seven Sins of Memory” goes all the way back to 1995 and the Oklahoma City bombing. We know that Timothy McVeigh was ultimately convicted and executed for his role in the bombing. But what some people who are old enough might remember is that in the days after the event, there was a manhunt for two individuals. They were called John Doe No. 1 and John Doe No. 2.

John Doe No. 1 turned out to be McVeigh. John Doe No. 2 was never found—or never found to be someone who was involved in the bombing—even though there was a drawing of him that was circulated by the FBI. So what was going on? Well, the initial description included McVeigh and another man, given by an eyewitness who was present at the body shop where McVeigh bought the van that he used to carry out the bombing. The witness distinctly recalled McVeigh was there with this other guy, whom he described in great detail. But what eventually they figured out was that this person was present in that body shop—but he was there on a different day than McVeigh. The eyewitness had the information about the two people exactly right, but he got the context wrong. This led to pretty significant memory error.

How could this happen?

Part of the argument we’ve made through my research at Harvard has to do with the role of memory in imagining the future. Here’s one of our findings: We put people in a functional MRI scanner—which allows us to look at brain activity associated with memory. And we ask them to remember past events in response, for example, to a cue word, or to imagine future events that might occur. And what we see is that many of the same brain regions become more active when we remember the past and when we imagine the future.

There are a lot of other similarities between the two. For example, many people with severe amnesia who have difficulty remembering the past also have difficulty imagining the future. And what we have argued is that our episodic memories—those memories of our past personal experiences—allow us to take bits and pieces of different experiences and recombine them to imagine and anticipate totally novel situations in the future.

The future is rarely identical to the past. So, if we want to use our past experience to anticipate new situations in the future, we need a flexible memory system that allows us to recombine elements. And our argument is that misattribution memories, like in the case of the Oklahoma City bombing, might be kind of a side consequence of this otherwise adaptive feature of memory that is very flexible.

We can take bits and pieces of the past, recombine them, run simulations of novel events in the future based on those past experiences. But, sometimes that flexibility of memory is going to result in memory errors.

So, people with amnesia about the past have trouble imagining the future? How so?

My first foray into this idea was actually stimulated by an observation back in the 1980s when I was at the University of Toronto. We were studying this very interesting patient who had had a head injury and a very severe memory deficit as a result. His name was Kent Cochrane. I tested Kent many, many times on a variety of tasks, and it was clear he could not remember any specific episode from his past. One day, the late Endel Tulving—a very well-known memory researcher who was my PhD mentor and who I worked with at the University of Toronto—and I were testing Kent. Tulving asked him this very innocent question: “What do you think you’re going to be doing tomorrow?” And Kent just sat there and said his mind was blank when he tried to think about what he might be doing tomorrow.

It was almost the same response he would give if you asked him, “What did you do yesterday?” He would say, “Well, my mind is a blank.” If you pushed him about the future, he might give you some generic response like, “Well, I’ll have breakfast and then I’ll have lunch.” But he couldn’t conjure up in his mind any specific episode of what he might do tomorrow any more than he could remember what he did yesterday. That was a very striking observation.

Later, in the early 2000s, when Donna Rose Addis arrived as a post-doc in my lab, we used functional MRI to show very striking similarities between when people remember the past and imagine the future. We’ve also seen this in behavioral studies. When we looked at people in their mid-60s into their mid-80s, and compared them to young adults in their 20s and 30s, we asked them to remember a past experience related to a cue word, such as “vacation.” Now you have a couple of minutes to tell me about your memory of a past vacation. You can try to recall it and tell me where you went and what happened. Or I could give you that same “vacation” cue and ask you to imagine a vacation you might take in the next few years.

The striking finding was that older adults, compared to younger adults, recalled fewer episodic details from their past experiences. That was a replication of a previous finding from other researchers—but the interesting new finding from that study was that when older adults tried to imagine a vacation in the future, they showed the same reduction in episodic detail. When they imagined future events, there was less information about what might happen, where it might happen, who might be there.

How does all of this relate to a person’s creativity?

After studying future imagining and its relation to episodic memory for close to a decade, we started to explore whether some of the same things might be true in the domain of creativity.

Creativity involves coming up with novel ideas—and that bears at least a family resemblance to imagining the future, where you’re imagining novel situations. We started doing experiments to show that, in fact, the capacity for episodic memory impacts one’s ability to perform standard creativity tasks.

For example, one of them is known as the “Alternate Uses” Task. So, I ask you to come up with novel uses of common objects like a coin or a brick. You get credit for being creative when you come up with a use that’s novel and also appropriate. And in several studies, we have provided evidence from cognitive manipulations that episodic memory seems to contribute to this performance on the Alternate Uses Task. We’ve reported that when we put people in the MRI and have them perform that task, we see activation in a couple of critical regions that are typically linked to memory, such as the hippocampus.

How can we improve our memory?

Remember, when we talked about encoding? Many studies have shown over the years that when you link up a new experience to things you already know—to try to relate this novel experience to what’s already in your memory—it boosts your ability to remember the information later on. So, make a conscious attempt to think about how this experience relates to past experiences. Think about how it changes your view of something that is familiar to you. Link it to people you know, places you know.

In cognitive psychology this is called elaborative processing, and it’s a big determinant of subsequent memory—carrying out that elaboration, rather than just letting an experience come and go and not doing much with it in terms of your internal cognitive processing.

Another way to improve memory is through the use of retrieval practice, sometimes referred to as the testing effect. That refers to the notion that retrieving information is a very good way to boost the subsequent recall of that information. So experiments have shown, for example, when you have people read stories and you test them on information from the story, they remember the information better compared to people who get a second shot at reading the story but weren’t tested on it.

That retrieval of information provides a basis for more enduring memory of that information over time. So, I think, trying to test yourself or frequently retrieve information is a very good way to boost the longevity of that information.

The 7 Sins of Memory

Three of the seven sins are sins of omission, which are different kinds of forgetting. They are called transience, absent-mindedness and blocking. Dr. Schacter explains:

Transience refers to the fact that all things being equal, we tend to have worse memory for things in the distant past than the recent past. Memories fade over time unless we retrieve them, rehearse them and think about them.

Absent-mindedness refers to a breakdown at the interface of attention and memory. We’re all familiar with this from everyday life: Where did I put my glasses? Where did I leave my phone? Because at the moment we took off our glasses or we put our phone down, we’re probably focusing on other things. The information is never really encoded into memory, and then we’re left with the frustrating episode of forgetting. But it’s forgetting that occurs for a very different reason than in the case of transience—information fading over time.

Blocking refers to cases where information hasn’t faded over time; it’s available in memory. You’re paying attention, you’re trying to remember, but you just cannot retrieve the information at the moment that you want it. Probably the most familiar example for most people would be blocking on the name of somebody you know: You know that you know the person; you know things about them. You just can’t come up with a name at the moment that you want it. Then it will pop into your mind at some later time, indicating that it’s there, but you just couldn’t get at it. That’s an “on the tip of my tongue” experience.

The other four sins of memory are sins of commission. These are cases where memory is present but either wrong or unwanted. Let’s go through them:

Misattribution occurs when we remember some aspect of an event but we get the source wrong. You might tell a friend that you just found out that your favorite band is playing a concert in your hometown. You might remember and tell your friend, “I heard it on the radio,” but in reality, somebody else personally told you about the concert. So you misattribute the source of the information (like the Oklahoma City bombing case explained above).

Suggestibility is a sin of commission that refers to cases in which some misinformation may be suggested to a person that becomes incorporated into their memory. For example, in a police investigation, a leading question about what happened in a past event might be asked based on an investigator’s hunch. They might suggest to the person something that then later is incorporated into that person’s memory, even though it didn’t actually happen. There’s been a lot of research on suggestion-induced false memories.

Bias refers to the fact that our recall of our past is skewed by our present knowledge, attitudes and beliefs. And that’s more of a subtle, but I think, pervasive aspect of memory—that what we currently know, believe and feel can skew our memory for what happened in the past.

Persistence refers to cases in which memory is present but unwanted. The best example of this would be an upsetting or traumatic experience that you witness or experience and you just can’t get it out of your mind. It might keep you up at night. In extreme cases of post-traumatic stress disorder (PTSD), it can actually lead to severe psychological dysfunction. One of the signatures of combat-related PTSD is persistent, intrusive memories.