Road safety campaigners could cut the death rate by
lobbying for cars to be made to look more like animals, and for
pedestrians at night to use fluorescent markers that highlight the
way they move.
In the study people detected changes to animals
quicker than changes to vehicles|
That is one implication of an experiment to show
that people have stone age brains that are unconsciously attuned to
detecting the movement of animals, rather than inanimate objects
such as cars, because the former played such a key part in the
survival of our ancestors.
The American study, published in the Proceedings of
the National Academy of Sciences, shows that the modern human brain
carries the visual priorities of our hunter-gatherer ancestors and
is still more likely to track a tiger- or even a chipmunk - than
cars and trucks, even though they see many more of the latter and
their lives now depend on noticing where they are on the
What our eyes look at is guided by brain mechanisms
that pick out some portions of a scene over others. Since keeping an
eye on predators and prey was crucial for survival during our
evolution, Joshua New of Yale University, working with Profs John
Tooby and Leda Cosmides of the University of California, Santa
Barbara, decided to study whether we learn what is important to
track or inherit it.
The researchers showed subjects pairs of photographs
of natural scenes in rapid alternation, with the second photograph
including a single change.
People were more than a second slower in detecting
changes to vehicles, silos or mugs than to more rarely experienced
animal species, such as elephants and pigeons.
"For example, we have two different savannah scenes,
one with a tiny elephant in the far distance that is very difficult
to see against the background trees, the other with a bright red
minivan in the foreground, taking up a much larger proportion of the
picture," explained Prof Tooby.
"Although both were appearing and disappearing from
the picture or flipping back and forth, people noticed these changes
to the elephant 100 per cent of the time, but almost 30 per cent of
people entirely missed these changes to the high contrast, bright
Overall, they were three times more likely to miss a
car, indicating that familiarlity and learning are not the source of
this difference. "This is the first high-level, category-specific
attentional system found for a stimulus class other than humans,"
they said. In other words, the brain is attuned to detecting
The bias to detect animals, the authors conclude, is
like the appendix: present in modern humans because it was useful
for our ancestors, even if useless now. But it could be exploited,
according to Prof Cosmides.
"It may seem fanciful, but it is possible that
painting cars to look more like animals might increase attentional
monitoring of them," she said.
"Have you ever seen those "flying tiger" airplanes
from WWII? (They have a tiger face painted on the front). They are
very hard not to look at."
Dr New added that pedestrians could do more to be
attention-grabbing at night. " We appear to be robustly prepared to
detect and accurately recognize biological motion (and particularly
people's) from very impoverished stimuli.
"By that, I'm referring to point-light displays in
which only small lights attached to a person's joints and limbs are
From that even a relatively few luminescent stickers
which indicate the entire body's motion (and that of my two dogs,
when I walk them at night) should make us (and our intended paths)
almost impossible to overlook (albeit pretty goofy looking)."
Road safety campaigners have to do more to take into
account how our brains are stuck in the distant past
"The ability to quickly detect changes in the state
and location of vehicles on the highway has life-or-death
consequences," concludes the paper, "yet subjects were better at
detecting changes to non-human animals, an ability that had
life-or-death consequences for our hunter–gatherer ancestors but is
merely a distraction in modern cities and suburbs."
The UK Department for Transport recently reported
that the number of people killed in road accidents was 3,172, among
258,404 road casualties in 2006.