Evidence that some animals are capable of “mental
time travel,” suggests they have a deeper understanding of the world
around them
Santino was a misanthrope with a habit of pelting tourists with rocks.
As his reputation for mischief grew, he had to devise increasingly
clever ways to ambush his wary victims. Santino learned to stash his
rocks just out of sight and casually stand just a few feet from them in
order to throw off suspicion. At the very moment that passersby were
fooled into thinking that he meant them no harm, he grabbed his hidden
projectiles and launched his attack.
Santino was displaying an ability to learn from his past experiences and
plan for future scenarios. This has long been a hallmark of human
intelligence. But a
recently published review paper
by the psychologist Thomas Zentall from the University of Kentucky
argues that this complex ability should no longer be considered unique
to humans.
Santino, you see, is not human. He’s a chimpanzee at Furuvik Zoo in
Sweden. His crafty stone-throwing escapades have made him a global
celebrity, and also caught the attention of researchers studying how
animals, much like humans, might be able to plan their behavior.
Santino is one of a handful of animals that scientists believe are
showing a complex cognitive ability called episodic memory. Episodic
memory is the ability to recall past events that one has the sense of
having personally experienced. Unlike semantic memory, which involves
recalling simple facts like “bee stings hurt,” episodic memory involves
putting yourself at the heart of the memory; like remembering the time
you swatted at a bee with a rolled up newspaper and it got angry and
stung your hand.
If an animal can imagine itself interacting with the world in the past
via episodic memory – like Santino recalling a failed attack when a
human spotted him holding a rock, or you remembering swatting at a bee –
it stands to reason that the animal might also be able to imagine
itself in the future in a similar scenario, and thus plan its behavior.
Santino might opt to hide his rocks, and you might decide to stop
antagonizing bees. The ability to represent oneself and one’s actions in
the mind’s eye – both in the past in in the future – is what scientists
refer to as
mental time travel.
Mental time travel is a vital skill in the arsenal of human
intelligence. When it goes right, we can devise and execute complex
hunting strategies that allow us to herd woolly mammoths into a canyon
for easy slaughter– something our ancestors excelled at in the late
Pleistocene. When it goes really right, we can spend years devising and
executing a plan to rocket astronauts through the coldness of space and
land them safely on the moon. If it turns out that other species might
have even the smallest hint of this ability, it raises the question of
just how much we might be underestimating their ability to interact
with, and understand, the world around them.
Zentall argues that mental time travel based on episodic memory has been
observed in a number of species, including non-human primates like
Santino, as well as dolphins, scrub-jays, rats, and pigeons. Scrub-jays
in particular seem skilled at planning their food hiding (caching)
behavior. In
experimental conditions,
they learned to cache food in areas where they knew they’d be hungry
the following day, and made sure that their favorite food was cached in
such a way that they’d always have access to it in the future.
But there is longstanding opposition to the idea of suggesting that
animals are capable of mental time travel. The University of Queensland
psychologist Thomas Suddendorf argues that despite “
ingenious attempts to demonstrate episodic memory or future simulation in non-human animals,” it still seems that “
there are few signs that animals act with the flexible foresight that is so characteristic of humans.”
While animals like scrub-jays might be able to adapt their behavior to
make the most of their food-caching, they do not display similar
flexibility outside of this narrow domain. Unlike scrub-jays, “humans,”
states Suddendorf, “can simulate virtually any event and evaluate it in terms of likelihood and desirability”
Zentall, however, has recently acquired a high-profile ally in Michael
Corballis, a psychologist at the University of Auckland who once
famously argued alongside Suddendorf that episodic memory was unique to
humans. It was
Suddendorf and Corballis who together coined the phrase
mental time travel in 1997, and established a
set of criteria that, if satisfied, could prove its existence in animals. By the age of 4, human
children satisfy these criteria
via their ability to choose the correct key to open a box that they’d
never seen before based only on experience with similar boxes and keys
in different locations in the past.
Animals
are typically only able to devise a similar solution after repeated
exposure to the same test materials in the same setting, which means
they might be solving problems via associative learning as opposed to
mental time travel.
Corballis revealed earlier this year that new evidence has come to light
that obliged him to change his mind as to whether these criteria had
been met in animals. The evidence that tipped the scale for Corballis,
however, was not found by observing animals’ behavior, but by measuring
their brains. “Mental time travel has neurophysiological underpinnings
that go far back in evolution, and may not be, as some (including
myself) have claimed, unique to humans,”
writes Corballis.
Recently published research
shows how brain activity in rats suggest that they might be envisioning
solutions to problems in their mind’s eye – in this case, an eye
located in their hippocampus. After the rats ran a series of mazes
during the day, researchers measured neuronal activity as they slept,
concentrating on the hippocampus – the part of the brain where the
mental map of the maze was stored. The rats appeared to not only be
replaying their past experiences running through the maze in their
sleep,
but also replaying the parts of the maze that they had only considered
running, but not actually run. For Corballis, this is neurological
evidence of mental time travel at work.
And yet, some behavioral evidence seems like convincing evidence of
mental time travel in animals, regardless of underlying brain activity.
In one experiment,
Bonobos and orangutans practiced using tools to retrieve food rewards –
like a juice bottle hanging on a string that was only reachable with a
hook. Knowing that they’d likely face a similar test situation the next
day, the apes took the appropriate tool with them to their sleeping
quarters and used it to retrieve their reward the next morning.
These skills do not seem a far cry from those employed by
early humans
to plan out the next day’s mammoth hunting excursion. Why then do we
not see more examples of animals engaging in behaviors that
unequivocally show the ability for mental time travel?
There’s more to the human intellect and ability to pull off successful
mammoth hunts and moon landings than episodic memory of course, and
other intellectual feats – not the least of which is our ability to
convey our thoughts and plans via language – appear absent in non-human
animals. There is also the question of how humans’ complex understanding
of our own and others’ minds might be involved. Mental time travel
likely requires some form of consciousness or self-knowledge to allow an
animal to place itself at the heart of its memories and future plans,
and much of this debate focuses on whether animals’ observed behavior or
neurological activity are evidence of consciousness at work.
Consciousness is the unknowable singularity at the heart of the black
box.
Zentall is confident that future research will provide evidence that
animals have skills like mental time travel that far exceed what we now
attribute to them. He is surely correct. But as we slowly pry open the
lid on the black box of animal minds, scientists will continue to
disagree as to what shapes they see emerging from the darkness.
Are you a scientist who specializes in neuroscience, cognitive
science, or psychology? And have you read a recent peer-reviewed paper
that you would like to write about? Please send suggestions to Mind
Matters editor Gareth Cook, a Pulitzer prize-winning journalist and regular contributor to NewYorker.com. Gareth is also the series editor of Best American Infographics, and can be reached at garethideas AT gmail.com or Twitter @garethideas.
ABOUT THE AUTHOR(S)
Justin Gregg, PhD, is a psychologist and Research Associate with the Dolphin Communication Project. His book,
Are Dolphins Really Smart? The Mammal Behind the Myth, was published this year with Oxford University Press. Follow him on Twitter
@justindgregg or via his blog at
justingregg.com
