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Matt Ridley is the author of provocative books on evolution, genetics and society. His books have sold over a million copies, been translated into thirty languages, and have won several awards.

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Mental time travel

The longer your past, the longer your future

My latest Mind and Matter column in the Wall Street Journal is about how the human brain deals with the future. Here it is with added links.

I recently came across the phrase "remembering the future." Rather than some empty poetic paradox, it appeared in an article about a neuroscientific experiment that tested a hypothesis of Karl Friston of University College, London, that the brain is more active when it is surprised.

In the study, volunteers watched patterns of moving dots while having their brains scanned. Occasionally, a dot would appear out of step. Although there was the same number of dots, the visual part of the subjects' brains was more active when the dots broke step. According to Arjen Alink of the Max Planck Institute in Frankfurt, Germany, who did the experiment, the brains were predicting what would happen next and having to work harder when their predictions failed. They were "remembering the future."

There is a growing conviction within neuroscience that one of the human mind's chief preoccupations is prediction. Jeff Hawkins, the founder of Palm Computing who is now a full-time neuroscientist, argued in his 2004 book "On Intelligence"that the mind does this by detecting a familiar pattern in its input, then anticipating from past experience what usually follows. The more unexpected something is, the more conscious we are of it.

This explains a lot about awareness. When I push my foot down on the brake pedal, I expect to feel deceleration. If I do, I am barely conscious of the fact: My mind continues to concentrate on the radio or my conversation with my passenger. If I don't, I am immediately so aware of the car skidding on the ice or the brakes failing that my mind is fully occupied with the failed prediction.

The big brains of human beings undoubtedly lead them to predict patterns further ahead than other animals. My dog is quite capable of expecting to be taken for a walk or given her dinner at certain times of the day. But she is not capable, as I am, of expecting cold weather in winter or predicting the need to pack a suitcase before a trip. Still, she probably has a longer view of the future than a guinea pig, which in turn sees further ahead than a frog.

Some birds stand out as exceptionally good at "mental time travel." The psychologist Nicky Clayton observed that western scrub jays steal food left behind by lunching students at the University of California at Davis. The jays hid the food by digging it into the ground. Sometimes they came back later and moved the food-but only if they had been observed by other jays when hiding the food in the first place. Dr. Clayton has since shown in her lab at Cambridge University that they do this to foil thieves, and that scrub jays are uniquely forward-thinking in this respect, even compared with other food-caching species of bird.

Dr. Clayton's other experiments with children reveal that this mental time travel becomes possible for human beings around the age of five. As adults, we inhabit longer futures than children, and longer pasts, too.

Daniel Schacter of Harvard University has made the remarkable discovery that the same parts of the mind hold both our episodic memories and our imagined futures. That is to say, if asked to imagine some specific future event, people activate the very same regions of the brain as they do when asked to recall some particular past event. Indeed, people who suffer strokes that affect these regions lose not just the ability to remember their own lives but the ability to imagine future possibilities as well.

Dr. Schacter concludes, much like Dr. Hawkins and Dr. Friston, that "a crucial function of the brain is to use stored information to imagine, simulate and predict possible future events." Through technology like writing and printing, the longer we extend the past, the longer our view of the future becomes. But that is a subject for another column.