“About what I’ll be doing
tomorrow?” N.N. replied.
“Yes. How would you
describe your state of mind
when you try to think about it?”
N.N. paused for a few more
seconds. “Blank, I guess,” he said.
;e very concept of the future,
seemed meaningless to N.N. “It’s
like being in a room with nothing
there and having a guy tell you to
go ;nd a chair,” he explained.
On the basis of his study of
N.N., Tulving proposed that projecting ourselves into the future
requires the same brain circuitry
we use to remember ourselves in
the past. Over the past decade,
as scientists have begun to use
f;;; scanners to probe the activity of the brain, they have found
support for his hypothesis. Last
year, for example, Tulving and
his colleagues had volunteers lie
in an f;;; scanner and imagine
themselves in the past, present,
and future. ;e researchers saw
a number of regions become
active in the brains of the volunteers while thinking of the past
and future, but not the present.
Studies on children also lend
support to Tulving’s time travel
hypothesis. Previous work had
shown that around the age of ;,
children start to develop a strong
episodic memory. ;omas
Suddendorf, a psychologist at
the University of Queensland in
Australia, designed a series of
experiments to see if foresight
develops with the same timing.
In one experiment, published
earlier this year, he showed
;- and ;-year-olds a box with
a triangular hole on one side
and demonstrated how to open
it with a triangular key. He
then swapped the box for one
equipped with a square lock and
gave the children three di;erent
keys. Most of the ;; subjects
correctly picked the square key,
regardless of their age.
;en Suddendorf ran the
experiment again, but with a
twist to test the children’s fore-
sight. Instead of choosing a key
for the square lock right away, the
kids were ;rst taken to another
room to play for ;; minutes;
only after that were they o;ered
a choice of keys, which they had
to take back to the room with
the box. ;e children had to
anticipate what would happen
when they tried to unlock it.
;is time Suddendorf found a
sharp break between the ;-year-
olds and the ;-year-olds. ;e
younger kids were just as likely
to pick one of the wrong keys as
the right one. ;e older kids did
much better—probably because,
with more developed episodic
memories, they remembered
the square lock and used that
knowledge to project into a
future in which only a square
key would unlock the box.
In brain scans of mental
time travel, scientists have
found that volunteers use
the same neural circuitry
to remember the past
and to imagine themselves
in the future.
to write down as many of the
listed words as they could. ;e
students asked to plan a camping
trip recalled more words than
the others. Klein says his results
illustrate the decision-making
value of memory: When students
were actively planning the future,
their memories worked best.
;;; ;;;;;;;;; ;; ;;;;;;
time travel may have evolved in
mammals more than ;;; million
years ago. Scientists can get clues
to its origins by studying lab
rats. When a rat moves around
a space—be it a meadow or a
lab maze—it encodes a map in
its hippocampus, a structure
located near the brain’s core.
Neurons there become active
at particular spots along the
route. When the rat travels that
route again, the same “place
cells” ;re in the same order.
In ;;;; a group led by Tom
Davidson and Fabian Klooster-
man, neuroscientists at ;;;,
observed rats as the animals
traveled along a winding,
;;-meter track. ;e researchers
were able to identify place cells
that ;red at di;erent spots all
along the way. From time to
time, the rats would stop on the
track for a rest. Davidson noticed
something intriguing: Sometimes
during these breaks the place
cells became active again, ;ring
in the same order (but at ;; times
the speed) as they did when the
rats were navigating the track.
It seemed that the rats were
rapidly replaying their journey
through the track in their heads.
