Remembering, to most of us, means recalling a past occurrence. But to Endel Tulving, PhD, the mechanisms of memory evoke the future as well. The reason? Memory allows us to mentally travel backward in time as well as into the future, explained Tulving, a University of Toronto professor emeritus and visiting professor in cognitive neuroscience at Washington University, in a presidential invited address at APA's 2003 Annual Convention in Toronto.
Tulving's theory stems from extensive memory research he's conducted since the 1950s at Toronto, Yale University and the Toronto-based Rotman Research Institute--and, he said, others' research supports it too. He proposed an official term for, and definition of, what makes such mental time travel possible:
Chronesthesia--A hypothetical brain/mind ability or capacity, acquired by humans through evolution, that allows them to be constantly aware of the past and the future.
Of course, Tulving noted, not all forms of memory--and there are many--are time-related. The "episodic" kind, involving recollection of past personal experience, is, he said. But the "semantic" kind, involving acquisition, retention and retrieval of facts, is not.
"You don't need mental time travel to remember a chemical formula or your mother's maiden name," he explained. "You can know a lot of things without mental time travel, but you can't remember events from your past, or anticipate your future, without it."
Tulving went on to explain how and why humans have adapted chronesthesia--a learned capability absent in other animals and human infants--to advance their survival. And he urged other psychologists to help build a research base on its workings.
Time travel's benefits
Over time, said Tulving, people discovered that recalling past events helped them learn what to avoid and how to behave in the future--its key feature, he said. In social relationships, for example, it enabled them to distinguish friends from foes; in the occupational and food-gathering arenas, it helped them to develop tools that worked well and to discard ones that didn't.
The higher-order process of chronesthesia, he explained, allows people to update information critical to surviving, thriving and dealing with changes in their world. In addition, it aids semantic memory by attaching personal stories to facts, giving people's experiences temporal and emotional dimensions, which make them more believable.
Nothing makes such benefits of chronesthesia more apparent than studying people who have suffered brain damage that impairs their mental time travel ability but does not affect other cognitive functions, said Tulving. He related the case of an amnesiac man, "K.C.," who had sustained multiple brain lesions, including hippocampal lesions, in a motorcycle accident.
The patient could solve math problems, but he couldn't remember ever taking a math class, or, for that matter, couldn't recall how he came to Tulving's office for an interview. Similarly, the patient knew from semantic memory that his family owned a lake house two hours away. But he had no memory of ever visiting it, and no idea when he'd likely return there.
The patient was missing the "human ability to project our own past into the future," said Tulving. That ability, he believes, has enabled us to create and pass down a wealth of cultural knowledge through the generations, including how to:
Provide the dead with grave goods--weapons, ornaments, utensils and the like that are buried with the dead for their use in the afterworld.
Make and keep records.
Formally educate the young (to benefit them in the future).
Create gods and invent ways of pleasing them.
Explore the stars.
As for hard scientific evidence of chronesthesia's existence, there's "zero, none, very little--it's just an idea," said Tulving. But, he said, emerging imaging research promises to help shed light on its brain mechanisms and has already suggested that higher-order thinking regions, such as the prefrontal cortex, are involved.
He admonished, however, that no function--chronesthesia or any other--"holds a particular seat in the brain; it's all over the place."
In addition, said Tulving, thought experiments and studies in developmental psychology and psychopharmacology, to name just a few areas, could begin to build a research base on what "pastness" has in common with "futureness."
After all, he said, "The kind of culture that Homo sapiens have created over the past 40,000 years or so can be produced only by individuals whose intelligence includes conscious awareness of the future in which they and their progeny will continue to live and survive."