Summary: April 3, 2007
Time in the Animal Mind
By CARL ZIMMER
Humans are born time travelers. We may not be able to send our bodies into the past or the future, at least
not yet, but we can send our minds. We can relive events that happened long ago or envision ourselves in the
New studies suggest that the two directions of temporal travel are intimately entwined in the human brain. A
number of psychologists argue that re-experiencing the past evolved in our ancestors as a way to plan for the
future and that the rise of mental time travel was crucial to our species' success. But some experts on animal
behavior do not think we are unique in this respect. They point to several recent experiments suggesting that
animals can visit the past and future as well.
The first clues about the twists and turns of mental time travel came from people with certain brain injuries
that caused them to forget autobiographical details without forgetting the information they had picked up
along the way. A man known in the scientific literature as K.C., for instance, could play chess with no
memory of having ever played it. K.C. could remember sentences psychologists taught him without any
memory of the lessons.
K.C. had lost what psychologists now call episodic memory. Endel Tulving, a Canadian psychologist, defined
episodic memory as the ability to recall the details of personal experiences: what happened, where it
happened, when it happened and so on.