Close your eyes and imagine what tomorrow is going to be like. You might not get it completely right, but you can probably sketch out a good approximation—when you wake up, how you get your coffee, getting the kids ready for school, feeding the dog, who you talk to at work or at home. It’s not hard to imagine what it might be like with some level of confidence.
For decades, some experts in psychology have argued that the imagining you just did—called “mental time travel”—is one of the things that makes humans special.
The concept was introduced in the 1980s by a psychologist named Endel Tulving, who focused his work on humans and found that people with certain kinds of brain injuries cannot engage in this kind of future imagining. The idea that mental time travel is unique to humans and “is one of the reasons humans have been able to dominate the environment and many other species on this planet,” as psychologist Jonathan Redshaw wrote in one paper, persists today.
But is it true? Psychologists and researchers who explore this question are divided. And the rift between them can teach us something about how we do science, how we think about animals, and how we might better think about the future.
Those who hold that the ability to move into the future in our minds is uniquely human believe we should assume, at a baseline, that humans are special. Researcher Thomas Suddendorf, author of a seminal 2007 paper on the topic, argues that this is simply good science. “While our children’s books and cartoons are full of stories of animals plotting the future, we are not bombarded with accounts of real animals in forests or farms, say, working to foil the bad guy’s evil plot, or of them scheming to escape from the zoo next summer when the conditions are right,” he told me via email. “So it would seem more sensible to start from the assumption of absence, and then set out to try to falsify that claim through studies that demonstrate competence.”
And yet, over the past few decades, research has shown that nonhuman animals are far more capable, aware, and intelligent than we once thought. Pigs can be optimistic or pessimistic, giraffes can use statistical reasoning, even cuttlefish can remember what, where, and when. Humans are, after all, animals too, and we’re linked by evolution. If there is a benefit to foresight, you might expect that evolution would encourage its development in other creatures as well. In fact, human children don’t seem to develop this skill until they’re about 4 years old. It seems a bit strange to assume that just because animals don't behave as they do in children’s books they aren’t capable of higher-level reasoning or imagining the future. (See the classic Onion article “Study: Dolphins, Not So Intelligent on Land.”)
But perhaps a bigger problem lies in the way this debate has been set up. Some experts in mental time travel define it in such a way that the question of whether other animals are capable is unanswerable. These folks argue that for a creature to truly have mental time travel, it must have what they call “phenomenological experience,” which is essentially consciousness and awareness of the mental process. The problem is that this experience is internal and private. You and I can’t know another human’s internal state of consciousness without asking (and sometimes even with asking). Without being able to have a long, philosophical chat with a creature about its internal state, we will never know if rats or birds or dolphins or monkeys have this ability. (I am reminded of research I did years ago on the debate over whether it was scientifically sound to say that individual animals had “personalities.” One researcher told me that you simply couldn’t say so because it has “person” in the word.)
English (US)