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In my previous post I suggested we shouldn’t feel guilty about our tendency to mind wander—we all do it, most of us for almost half of our waking hours! So why have we developed minds that wander so much? The jury is still out on this, but one possibility is that our minds become exhausted if they are always concentrating. They need a break, just like our bodies. There are more enticing possibilities; mind wandering might have positive functions other than just rest. Mind wandering allows us to mull over our past mistakes and indeed our glories, and this could help us prepare for doing better next time we are involved in that activity. And then there is mental time travel. Without mind wandering both back to the past and forward into the future, we could not plan future events. The way we plan, for example, a wedding, is to rely on our past to work out the best way to approach the future event. Mind wandering, the day-dreaming sort, allows us to escape from real life occasionally, just like reading or watching a movie. We can wander back to the past when we were young and fit and could climb mountains, or if we’ve yet to climb a mountain, we can imagine doing it, based perhaps on documentaries we’re seen along with smaller hills we have succeeded in climbing.
We can travel back into our pasts and replay lovely moments, as often as we like, and why not? As long as we don’t allow these day dreams to take over our lives, they do no harm, and they may do a lot of good. The grief process after the death of someone you love would be a much harder process if we did not have the capacity to relive in our wandering mind the happy times. Many elderly people, even those with healthy minds but especially those in the early stages of dementia, often spend a lot of time “in the past.” For people with dementia and consequent memory problems, this is in part because they have lost the ability to remember recent events, but if it makes them more content, why not encourage them to wander in the past, perhaps helped by old photos and videos of their younger days.
Mental time traveling into the future is especially helpful for preparing ourselves for new and sometimes nerve-racking tasks. We all use mind wandering to rehearse how we are going to manage future events that we are feeling unconfident about; for example, a job interview or meeting the president of the U.S. Sports psychologists utilize controlled mind wandering to assist their sporting clients to rehearse in their minds the moves they are going to make in the future when they have to perform in real time. Apparently this can be very effective, and in fact, imaging specific actions can activate some of the same brain systems that are later activated when the person is actually performing the task.
Fifteen years ago, neuroscientists thought that when the mind was not focused, any electrical activity was simply noise, and in studies of brain activity, this noise could be subtracted from the electrical activity measured when the brain was focusing on a task. However, various sophisticated methods for tracking blood flow in the brain, which is assumed to correlate with the parts of the brain that are most active, have shown that the brain is almost as active when we are not focusing on anything in particular, as when we are concentrating. The parts of the brain that are active when our minds are in a relaxed state, or mind wandering, is called the default-mode network; this covers large regions of the brain, mainly in areas not directly involved in perceiving the world or responding to it. Apart from the default-mode network in the brain, in order to mind wander and mentally time travel, we require memory. Memory is mediated by a structure called the hippocampus, which turns out to be an essential part of the default-mode network. If your hippocampus is destroyed on both sides of your brain, you will no longer be able to make or recall new memories. One very famous American patient I worked with, known as HM (I’ve written a number of posts about his case) had his hippocampus removed on both sides of his brain in an effort to cure his epilepsy. After his surgery, he could no longer make new memories. In fact, it was because of HM that we learned what the hippocampus was for; too late I fear for HM, but it stopped neurosurgeons from removing the hippocampus on both sides of the brain ever again. HM lived entirely in the moment; he could hold a conversation from moment to moment but could not remember anything that happened more than 7 seconds ago. He was unable to imagine the future or recall much of the past, and he had no ability to mind wander. Our ability to travel mentally into the past and future gives us our sense of time. By traveling backward in time and re-experiencing how we used to be, then forward through the changes in our lives, and even into the future as we imagine the sort of person we want to become, we form our ever evolving sense of self. HM, stripped of memory and the ability to mentally time travel, had no sense of time. He lived in a time vacuum. Time was meaningless to him. Although he did have a limited sense of self, it was stuck in his childhood and teenage years, the only part of his life he had any memories of.
Storytelling is a unique human ability that relies on mental time travel. Stories allow us to share intricate narratives with others. These may be true stories, imaginary stories, or a combination. Stories permit the storyteller to take the audience on a guided tour, but the stories themselves require the mind of the teller to wander back to the past and into the future. Without the ability to mind wander to different times and places, we would not be creative.
One of the most valuable aspects of mind wandering is that it allows us to wander into other people’s minds, to “know” in a sense what others are thinking. We don’t actually “know” for sure what our best friend is thinking, but because of our own experiences and our knowledge of that person in particular and people like her in general, we can imagine what she is probably thinking and feeling in a particular situation. Psychologists call this “Theory of Mind.” This is the basis of empathy and communication. We often think of it as intuition. Some people are better at it than others, women often better than men. Autistic people and people with Aspergers have significant problems on tests of Theory of Mind and similarly have difficulty knowing what others are thinking and feeling. Wandering into other people’s minds is a skill that good actors and novelists must have, as well as good therapists.
Is mental time travel unique to humans or do animals experience it as well? This is hard to study, as animals and birds can’t talk to us and tell us what they are thinking or daydreaming about. Many activities animals do, such as squirrels storing nuts for future, perhaps suggesting that they are thinking forward in time, is probably instinctive behaviour. Instinct can drive very complex behaviours, including elaborate courtship behaviours, nest making, storing food, and flying or swimming great distances every year to breed or feed. These behaviours are all designed to improve survival and do not require mental time travel. However there are a few cases of great apes who truly do seem to be able to imagine future events. For example, a male chimp in Sweden called Santino gathered stones and hid them before visitors to the zoo arrived, so that he could fire them at people later. Charles Darwin described a baboon at the Cape of Good Hope who prepared mud missiles that he later threw at people. Some animals and birds make tools that they later use for extracting ants or honey. But the few examples that seem to imply that some animals can imagine the future do not begin to approach the complexity of the rich mind wanderings of humans, and the stories they can tell. But of course there may yet be a lot to learn about non-human animals. If only we could understand and speak their language…
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