Wikipedia Deep Dive

Mental time travel

17 min read

Right now, as you read these words, you are doing something extraordinary. You are here, in this present moment—but you could, if you wished, close your eyes and return to your childhood bedroom. You could smell the particular scent of that space, hear the sounds that drifted through the window, feel the texture of the bedspread under your fingertips. Or you could leap forward instead, imagining yourself next week, next year, or in some distant future that hasn't yet arrived.

This ability—to unstick yourself from the present and wander through the corridors of your own personal timeline—is what psychologists call mental time travel. And it may be one of the most remarkable things your brain can do.

The Discovery of a Hidden Superpower

The term "mental time travel" was coined by two researchers, Thomas Suddendorf and Michael Corballis, who were building on earlier work by the cognitive psychologist Endel Tulving. Tulving had spent years studying something called episodic memory—our ability to remember specific events from our own lives—and he proposed an alternative name for this phenomenon: chronesthesia, from the Greek words for time and sensation. But "mental time travel" stuck, perhaps because it captures something essential about what the experience actually feels like.

We are, in a very real sense, time travelers. Not in the science fiction sense of physically moving through time, but in the mental sense of being able to project our consciousness backward and forward along our personal timeline.

What makes this ability so fascinating is that it operates in both directions. Most of us think of memory and imagination as completely different mental activities. Memory looks backward; imagination looks forward. But research over the past few decades has revealed something surprising: these two capacities are deeply intertwined. They share the same neural machinery, develop along the same trajectory in children, and break down in similar ways when the brain is damaged.

The past and the future, it turns out, are not as different as they seem.

Two Kinds of Knowing

To understand mental time travel, you first need to understand the difference between two types of memory that psychologists have identified.

The first is called semantic memory. This is your storehouse of facts and knowledge about the world—the kind of information you might find in an encyclopedia. You know that Paris is the capital of France, that water freezes at zero degrees Celsius, that Shakespeare wrote Hamlet. This knowledge doesn't come attached to any particular memory of learning it. You simply know these things.

The second type is episodic memory. This is fundamentally different. Episodic memories are not abstract facts but vivid, first-person experiences. You don't just know that you attended your best friend's wedding; you remember being there. You can see the flowers, hear the music, feel the emotion that welled up when the vows were exchanged. You are mentally present at the scene.

Tulving described this distinction using two different kinds of consciousness. Semantic memory involves what he called "noetic" consciousness—a knowing awareness. You know facts, but you don't relive anything when you access them. Episodic memory, by contrast, involves "autonoetic" consciousness, from the Greek for self-knowing. When you engage episodic memory, you are not just knowing something—you are re-experiencing it. You travel back in time and become the person who lived through that moment.

Here's the crucial insight: mental time travel is specifically about this autonoetic, self-experiencing form of consciousness. And it works for the future just as it does for the past. When you imagine yourself at next year's holiday gathering, you are not just knowing abstractly that such an event will occur. You are projecting yourself into that scene, seeing it through your own eyes, feeling what it will be like to be there.

This forward-facing version of episodic memory has its own name: episodic foresight, or sometimes episodic future thinking.

The Theater in Your Mind

Researchers have found remarkable evidence that remembering the past and imagining the future are two sides of the same cognitive coin. When scientists use functional magnetic resonance imaging—a technique that reveals which parts of the brain are active during different mental tasks—they discover striking overlaps between remembering and imagining.

A study led by Donna Rose Addis examined what happens in the brain when people either recall past events or construct imagined future events. She found that both activities engage many of the same neural regions. The brain doesn't seem to distinguish sharply between "what happened" and "what might happen." Both require the construction of a mental scene, populated with sensory details, located in a specific time and place.

One way to think about this is to imagine your brain as a theater. When you remember the past, your brain assembles a kind of theatrical production—reconstructing the scenery, placing the actors on stage, and running through the events. When you imagine the future, the brain does essentially the same thing, except now it's creating an original production rather than reviving a classic.

The raw materials are the same in both cases: sensory impressions, spatial information, emotional associations, knowledge about how the world works. The brain takes these elements from its vast storehouse and recombines them to create a coherent scene. Whether that scene is drawn from memory or invented for a possible future is almost secondary to the fundamental process of scene construction.

This explains something curious about memory that scientists have known for a long time: memories are not perfect recordings. Every time you remember something, you are reconstructing it anew, and the reconstruction can be influenced by your current knowledge, emotions, and expectations. Memory is a creative act, not a playback function. And that makes perfect sense once you understand that memory and imagination share the same neural architecture.

The Geography of Time in the Brain

Neuroscientists have mapped out which brain regions are involved in mental time travel, and the picture is complex but revealing.

The hippocampus—a seahorse-shaped structure deep in the temporal lobe, famous for its role in memory—turns out to be crucial for both remembering and imagining. But intriguingly, the two hippocampi (there's one on each side of the brain) appear to play different roles. The left hippocampus is active when constructing both past and future events. But the right hippocampus shows a curious pattern: it is actually deactivated when people reconstruct past events, and only comes online when they're creating future scenarios.

This asymmetry suggests that imagining the future may require a kind of creative construction that remembering the past does not. The future is unknown, so the brain must work harder to generate a plausible scenario.

Other brain regions play important supporting roles. The ventral medial prefrontal cortex—a region near the front of the brain, just behind the forehead—becomes particularly active when people imagine future events that are personally meaningful to them, events related to their own goals and aspirations. This makes sense: when we think about the future, we're not just running mental simulations. We're imagining versions of the future that matter to us, that we want to bring about or avoid.

The posterior cingulate cortex, located toward the back of the brain, also lights up during future thinking. This region is part of what's called the default mode network—a set of brain areas that become active when we're not focused on the external world but are instead turned inward, daydreaming, reminiscing, or planning. The default mode network appears to be the neural home of mental time travel.

The Evolutionary Puzzle

If mental time travel is such a powerful ability, where did it come from? How did it evolve? And perhaps most provocatively: are humans the only animals who possess it?

Some researchers believe that mental time travel may be one of the defining characteristics of human cognition—perhaps even the prime mover of human evolution. The ability to imagine future scenarios would have given our ancestors an enormous advantage. They could anticipate dangers before they arrived, plan complex hunting expeditions, prepare for seasonal changes, and coordinate long-term projects with others.

If this ability is uniquely human, then it must have evolved sometime in the last six million years, after our lineage split from the lineage leading to modern chimpanzees. Some researchers point to the Acheulean hand axes created by Homo erectus, our ancestor who lived roughly two million years ago, as the first hard evidence of mental time travel in the fossil record. These stone tools are sophisticated objects that appear to have required planning and foresight to create. They weren't simple opportunistic implements but carefully crafted devices, often made in one location and carried elsewhere for future use.

But the question of whether animals can engage in mental time travel remains fiercely debated.

Can Animals Travel Through Time?

One influential idea in this debate is called the Bischof-Köhler hypothesis, named after two German psychologists who proposed it. The hypothesis suggests that non-human animals are stuck in the present. They can respond to their current needs and desires, but they cannot act on future needs they don't currently feel. A fully quenched animal, for instance, would not seek out water just because it might be thirsty tomorrow.

If this hypothesis is correct, it would mean that mental time travel is indeed uniquely human. But the hypothesis has been challenged by a number of studies claiming to show foresight in various animal species.

Consider the western scrub jay, a corvid—a member of the crow family. These birds are famous for caching food, hiding it in various locations to retrieve later. But the question is whether this behavior represents genuine planning for the future or simply an automatic, instinctive response.

Nicola Clayton and her colleagues at Cambridge University designed clever experiments to test this. They found that scrub jays appear to remember not just what food they cached and where they cached it, but when they cached it. This matters because different foods spoil at different rates. The jays seemed to prefer fresh food over spoiled food, suggesting they were keeping track of the passage of time—a key component of episodic memory.

Even more impressive, the jays appeared to plan for future needs. In one experiment, the birds were given food in the evening but learned that one compartment of their cage would have food in the morning while another would not. The jays began caching food preferentially in the compartment that would be empty in the morning—apparently anticipating their future hunger.

Studies with great apes have produced similar intriguing results. Mathias Osvath conducted experiments with chimpanzees and orangutans in which the apes were presented with a food reward and a tool that could be used to obtain a different, better reward later. Remarkably, the apes often chose the tool over the immediate food reward, apparently anticipating that the tool would be more valuable in the future.

Another study, led by Gema Martin-Ordas, found that apes could remember not just what happened and where it happened, but when it happened—forming integrated what-where-when memories that are a hallmark of episodic memory in humans.

But critics remain skeptical. They argue that these behaviors might be explained by simpler mechanisms, like associative learning—the animals learn that certain actions lead to certain outcomes without necessarily imagining future scenarios in the rich, experiential way that humans do. The debate continues, and the truth may be that some animals have some capacities for future thinking while lacking the full-blown mental time travel that humans possess.

How Children Learn to Time Travel

If mental time travel is a sophisticated cognitive ability, you might expect it to take time to develop. And indeed, research shows that children acquire the capacity for mental time travel gradually over the first years of life.

The various component abilities don't all come online at once. Instead, they emerge piece by piece, like the parts of a complex machine being assembled. By around age four, most of the essential psychological components appear to be in place. This includes something particularly interesting: the ability to prepare for two mutually exclusive possible futures.

Think about what this means. A young child who can only deal with one possible future is stuck in a simpler mental world. But a child who can simultaneously consider multiple possible scenarios—understanding that tomorrow might bring sunshine or rain, and preparing for both—has taken a crucial step toward genuine foresight.

Two and three-year-old children can talk about upcoming events in basic ways, but their understanding is limited. By four and five, children become much more fluent in discussing future situations. But researchers have worried that verbal reports might not capture the whole picture. Perhaps children understand more than they can articulate, or perhaps they say things about the future without really grasping what they mean.

To address this, scientists have designed experiments that require children to demonstrate foresight through their actions rather than their words. In one carefully controlled study, four-year-olds were shown a problem in one room and then, later, given the opportunity to select a tool in a different room that could solve that problem. The children succeeded, demonstrating that they could remember a past problem well enough to prepare for solving it in the future.

These capacities continue to develop throughout childhood and adolescence. The ability to imagine distant futures, to construct detailed and coherent scenarios, to integrate multiple sources of information into a plan—all of these become more sophisticated as children grow. Mental time travel is not a single ability that switches on at a particular age but a constellation of skills that develop gradually over many years.

Why Does This Matter?

Mental time travel isn't just a curious quirk of human psychology. It underlies some of our most important cognitive abilities.

Consider planning. Any time you make a plan, you are engaging in mental time travel, projecting yourself into a future scenario and thinking through what you'll need to do. The same is true of navigation—not just physical navigation through space, but navigation through life, choosing paths and anticipating where they'll lead.

There's also what psychologists call affective forecasting: predicting how you'll feel in the future. When you imagine how happy you'll be if you get that promotion, or how devastated you'll feel if a relationship ends, you're engaging in a form of mental time travel. These predictions influence your decisions in the present, even if they turn out to be inaccurate (which, research shows, they often are).

Counterfactual thinking—imagining how things might have gone differently—is another form of mental time travel, this time into alternative pasts. When you think "if only I had left five minutes earlier," you're constructing a scenario that didn't happen but could have. This kind of thinking is crucial for learning from mistakes and understanding causation.

Prospective memory—remembering to do things in the future—also depends on mental time travel. When you make a mental note to pick up milk on the way home, you're imagining a future version of yourself at the grocery store. Without this ability, you'd be trapped in an eternal present, unable to form intentions that stretch across time.

Even intertemporal choice—deciding between a smaller reward now and a larger reward later—requires mental time travel. You have to be able to imagine your future self enjoying that larger reward vividly enough to resist the temptation of the immediate one.

The Limits of Looking Forward

Studying mental time travel presents researchers with significant challenges. How do you measure someone's ability to remember the past or imagine the future?

For episodic memory, scientists often ask people to describe past events from their own lives. Some studies then try to verify these memories by comparing them to the accounts of family members or friends who shared the experience, or by checking against public records. But verification isn't always possible, so many studies focus instead on the qualities of people's descriptions—how detailed and specific they are, whether they contain the vivid sensory and emotional elements that characterize genuine episodic memories.

Several standardized measures have been developed. One approach assesses how fluently people can generate personal memories from different time periods—last week, last year, the past five years. Another uses a scale to rate memories from highly specific to very general. A third, called the Autobiographical Interview, tries to separate the truly episodic elements of a memory from the semantic, factual elements.

Measuring episodic foresight is even trickier. Most measures have been adapted from measures of episodic memory—which makes sense, given the deep connection between the two capacities. But there's a fundamental limitation: with future events, you can't verify accuracy in the same way you can (sometimes) verify memories. An imagined future event either hasn't happened yet or may never happen at all.

This is a significant problem because it means we can study the richness and detail of people's future imaginings without knowing whether those imaginings are realistic or useful. Studies with children and animals get around this problem by requiring participants to demonstrate foresight through their behavior—to actually do something that shows they were thinking ahead. But with human adults, researchers have largely relied on verbal descriptions, with all their limitations.

The Binding of Time

Perhaps the most profound implication of mental time travel is what it suggests about human consciousness and identity. We are beings who exist not just in the present moment but across time. Our sense of self extends backward into memory and forward into anticipation.

Philosophers have long puzzled over questions of personal identity: what makes you the same person you were ten years ago, or will be ten years from now? Mental time travel may be part of the answer. It's the thread that stitches together the scattered moments of our lives into a continuous narrative. When you remember your past and imagine your future, you're not just accessing information—you're maintaining the coherence of your self across time.

This connection to identity may also explain why mental time travel is linked to our capacity for making free choices. To choose meaningfully, you need to be able to imagine different possible futures and select among them. A being without mental time travel would be a being without genuine choice, buffeted from moment to moment by immediate circumstances with no ability to step back and consider alternatives.

And there's something almost paradoxical about the relationship between mental time travel and the present moment. We can only engage in mental time travel here, now, in the present. Yet the very act of mental time travel takes us out of the present, allowing us to inhabit times that don't—or don't yet—exist. We are creatures simultaneously bound to the now and freed from it, anchored in the present yet capable of sailing the waters of time.

This capacity may be, as some researchers suggest, one of the most distinctive features of the human mind. Whether it evolved as an adaptation for planning and survival, or emerged as a byproduct of other cognitive developments, or arose through some complex interplay of factors we don't yet understand, it has become central to what it means to be human.

You are a time traveler. You have been one all along. And every time you remember yesterday or dream of tomorrow, you exercise an ability that may be your birthright as a member of our curious, forward-looking, backward-glancing species.