Have you ever forgotten a lunch date and stood up a good friend? This can be embarrassing and disconcerting, a potential sign that your memory just isn’t what it used to be.

Woman smiling up at memory cloud on blackboard behind her

But, according to a new book by researcher Charan Ranganath, Why We Remember, this kind of gaffe is less about a faulty memory and more an artifact of how memory works.

“Although we tend to believe that we can and should remember anything we want, the reality is we are designed to forget,” he says.

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As Ranganath explains, our memory isn’t just a repository for everything that’s ever happened to us; it’s much more fluid than that, affected by the context of our past experiences as well as what’s happening in the present moment. Because our lives are full of incoming sensory information and our reactions to it, the laying down of a memory needs to be a competitive process, with priority given to more important, novel, or salient experiences at the expense of others. That’s why we might forget about our lunch date in the midst of a pressing work deadline.

Ranganath argues that if we understand how and why we remember things, we’ll be better prepared to use our memories wisely. And, he writes, this is important, as memory plays a pretty all-encompassing role in nearly every aspect of our lives.

“[Memories] are the driving force behind life-changing decisions, from what career to pursue and where to live to what causes you believe in, even how you raise your children and what sort of people you want around you,” he says.

How memory works

Because memory is so important, many parts of our brains are involved in creating memories—most notably, the hippocampus and prefrontal cortex—working together to help keep track of our lives and make future predictions.

The hippocampus is the primary center of memory, laying down “episodic memories,” based on specific experiences within particular contexts (such as when and where something occurred). Because it uses context to index a memory, the hippocampus plays a role in orienting us in time and space. This means people with damage to the hippocampus, such as those with Alzheimer’s, have trouble with getting lost and are often disoriented. However, even with an intact hippocampus, you might wake up in a strange hotel room and feel disoriented for a moment. The difference is that you can quickly draw on episodic memory to recall why you’re there.

Recalling episodic memories allows you to “time travel,” in a way, re-experiencing feelings and thoughts you had at different times in your life. Because they are context-driven, these memories can be triggered by putting yourself in a similar context to where an event occurred. For example, you might walk into your childhood home and smell your mother’s cooking and be transported to a powerful memory of eating dinner with your parents when you were a child (and the good or bad of that experience). Music is also a powerful way to stir up episodic memories, with songs from our teen to early adult years being particularly potent.

Current emotions affect memory, too, says Ranganath, so that feeling sad may lead to recalling sad memories. And you can affect your feelings in the present by recalling the past, such as when you think back nostalgically about a trip you took abroad and relive the happy memories. Research suggests that reminiscing can be good for your mood and sense of self, if you focus on positive memories (which, fortunately, are easier to recall). And, if we recall past experiences of being generous, for example, it can make us more generous in the present.

The prefrontal cortex is also important for memory, especially “semantic memory”—the consolidation of memories from the past that can be used to understand our present self and our circumstances and to make predictions. It’s implicated in learning and in directing our behavior, helping us to navigate our lives. So, while the hippocampus might contain memories of the many places we’ve left our house keys in the past, the prefrontal cortex might recognize a pattern in those memories and help us know where to look for a lost pair. It may also notice a pattern of memory lapses, signaling us to be more careful in the future.

In that way, the prefrontal cortex assists in weeding what we can let go of from what we most need to know, helping us make good choices.

“The human brain is not a memorization machine; it’s a thinking machine,” says Ranganath. “We organize our experiences in ways that allow us to make sense of the world we live in.”

How to improve memory for things we want to remember

The important thing isn’t to remember everything, writes Ranganath, but to remember what we most value. Luckily, there are many ways we can improve our memory for things that matter to us.

Why We Remember: Unlocking Memory's Power to Hold on to What Matters (Doubleday, 2024, 304 pages)

Taking good care of our physical bodies (getting enough food, exercise, and rest, for example) will improve our brain health generally, and so improve memory, says Ranganath. But we can also use the nature of memory to make certain memories stand out.

Events are more memorable when they are novel or surprising. So, if we want to draw on a memory later, we can focus more on unexpected things in an experience. For example, going to a new restaurant with your romantic partner will make the experience more memorable than going to a favorite hangout, where you often dine. And, since we tend to remember events imbued with stronger emotions—higher highs and lower lows—that can also play a role in creating a lasting memory.

When it comes to learning, we can use mnemonic devices to remember things that may otherwise be difficult to recall, such as using the phrase “King Philip came over for good spaghetti” to remember taxonomy categories (kingdom, phylum, class, order, family, genus, species). Chunking large bits of information into more manageable pieces—a trick often used by memory savants—can also be useful, says Ranganath. It’s the reason our phone numbers and social security numbers are broken up into three sections, to make them easier to remember.

However, memory isn’t just about recall; it’s about thinking through things and seeing connections between disparate elements. So, our brains are designed to organize memories into fuller narratives or schemas that help us make sense of the present and know what to do. This is why a seasoned basketball player can “read” their opponents’ positions on the court and instantly initiate the right play. Schemas formed through past experiences of thousands of plays on the court help them predict what will happen in the future if they make a particular move.

Memory also isn’t as objective and unchanging as we think, in part because our brains reconstruct a memory each time it’s recollected. While memories may be based on bits and pieces of what actually occurred in the past, they can also be embellished by our minds, based on what we think probably happened or what we imagine could have happened. This is why two people can remember something they experienced together so differently—something that can be both entertaining and exasperating.

“Each time we revisit the past in our minds, we bring with us information from the present that can subtly, and even profoundly, . . . alter the content of our memories,” says Ranganath. “Consequently, every time we recall an experience, what we remember is suffused with the residue of the last time we remembered it.”

Factors like how recently something happened, how much something is repeated, and how we are feeling at the time will change how well we recall a memory. Also, the people around us can affect our memory for an event, by either sharing their own memory (which may contradict ours) or by their expectations of how an event should be remembered. That’s why two people witnessing a street fight may see different things occurring, but eventually come to have similar memories about what happened. Their memories influence each other, more so if they talk it through after the fact.

Being able to update our memories when we get new information is not a bug but a feature of memory. Unfortunately, that means memory can be easily corrupted, too, says Ranganath. For example, eyewitness accounts of crimes can be influenced by the kinds of leading questions witnesses are asked by law enforcement and by their feelings of fear or stress in the moment. That can lead someone to mistake an innocent person for a criminal, with terrible consequences. Similarly, there are many cases of people who’ve confessed to a crime simply because they became convinced through coercion that they shouldn’t trust their own memory of what happened.

While we can (and do) use our memory to remember important lessons from life and make good decisions, we must also be humble when it comes to our memory. By understanding the way memory works, we can learn to strengthen it for the things we need to know and to avoid some of the pitfalls.

“When we get to know the remembering self, we can seize the opportunity to play an active role in our remembering, freeing ourselves from the shackles of the past, and instead using the past to guide us toward a better future,” says Ranganath.

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