The ability to "see" oneself in the future is a remarkable human trait -- some would say unique -- that is not well understood. That's despite the fact that we probably spend as much time thinking about the future as we do thinking about the present.
Now new research from Washington University in St. Louis suggests that it's precisely because we can remember the past that we can visualize the future.
"Our findings provide compelling support for the idea that memory and future thought are highly interrelated and help explain why future thought may be impossible without memories," says doctoral candidate Karl Szpunar, lead author of a report on the research in the Jan. 1 issue of the Proceedings of the National Academy of Sciences.
The findings are consistent with other research showing that persons with little memory of the past, such as young children or individuals suffering from amnesia, are less able to see themselves in the future.
"Specifically, individuals, be they depressive patients, young children, or amnesiacs, who are unable to vividly recollect their past also seem to be unable to form specific mental images of the future," the researchers say in their report.
"If you have an amnesic person who can't remember the past, they're also not at all good about thinking about what they might be doing tomorrow or envisioning any kind of personal future," adds Kathleen McDermott, principal investigator for the university's memory and cognition lab and a co-author of the report.
The researchers base their conclusions on brain scans of 21 college students who were cued to think about something in their past, and anticipate the same event in the future, like a birthday or getting lost. The experiment was carried out as each student lay prone in a magnetic resonance imaging machine, a dreadful but very useful contraption that can show which areas of the brain are stimulated during specific thought processes.
The students were also asked to picture former President Bill Clinton in a past and future setting. Clinton was chosen because he was easily recognized and familiar to all the students.
The researchers found a "surprisingly complete overlap" among regions of the brain used for remembering the student's past and those used for envisioning the future. And every region involved in remembering was also used in anticipating the future.
In a nutshell, the researchers isolated the area of the brain that "lit up" when the students thought about an event in their own past. And more importantly, that same area lit up again when they thought about a similar event in their future. In fact, the researchers report, the brain activity was so similar in both cases that it was "indistinguishable."
Thus our memories are essential to our ability to see ourselves in the future, a trait that has become enormously useful down through history, and may partly account for the evolutionary success of Homo sapiens. As McDermott notes, "this ability to envision the future has clear and compelling adaptive significance."
Without our impressive memory banks, we wouldn't know what we need to do today to cope with what's likely to happen tomorrow. But we do have those memories, and we can project ourselves into the future, and that is a very useful capability.
The findings were reinforced when students contemplated Bill Clinton. Since none of them knew him personally, their memories were not autobiographical. And the brain scans showed "significantly less" correlation between memories of having seen pictures of Clinton in the White House and projecting him into the future.
So this "time machine," as the researchers describe it, allows us to use the past to see ourselves in the future, and both our memories and our anticipation are interdependent.