Multitasking while driving may exceed brain's capacity

There are obvious examples in this newsgroup of people who try to
think and type at the same time, thereby exceeding their own ability
to do either.


Shifting priorities at the wheel
By Bruce Bower
April 24th, 2008



Multitasking while driving may exceed brain's capacity

A special corner of hell is reserved for drivers who weave from one
lane to another at a crawl while blithely chatting on their cell
phones. Even a simple form of multitasking — driving while listening
to someone else talk — disrupts the ability to navigate a car safely,
a new study finds.

An intriguing neural response underlies vehicular mishaps associated
with such distractions, say neuroscientist Marcel Just of Carnegie
Mellon University in Pittsburgh and his colleagues. Attending to what
someone says galvanizes language-related brain areas while
simultaneously reducing activity in spatial regions that coordinate
driving behavior.

This finding suggests that people who combine relatively automatic
tasks, such as speech comprehension and car driving, exceed a
biological limit on the amount of systematic brain activity they can
accommodate at one time, the researchers propose. As a result, the
less-ingrained skill — in this case, driving, which is learned long
after a person grasps a native language — takes a neural hit.

“What’s exciting is that now we have a biological account of how
multitasking affects driving behavior,” Just says.

The new findings appear in the April 18 Brain Research.

If merely listening to someone talk dents the ability to maneuver a
car, then other common driver activities may do the same, Just
suggests. These behaviors include tuning or listening to a radio,
eating and drinking, monitoring children or pets, and conversing with
a passenger.

Cell phones stand out as particularly problematic for drivers, Just
notes. Cell phone conversations require a driver’s constant attention
in order not to appear rude or insulting to an unseen partner. In
contrast, a talking passenger can willingly cut off conversation upon
spying an approaching ambulance or some other demand on a driver’s
attention.

Psychologist David Strayer of the University of Utah in Salt Lake City
agrees, adding that the new results offer a conservative estimate of
the neural impact of multitasking on driving. Strayer and his
colleagues have documented steep declines in simulated driving skill,
as well as a marked drop in driving speed, among volunteers using
handheld or hands-free cell phones.

Just’s team studied 29 adults, ages 18 to 25. Each participant lay in
a functional MRI scanner equipped with a screen that displayed a
simulated driving exercise. These machines measure blood-flow changes
in the brain, providing indirect signs of rises and falls in neural
activity.

In one trial, volunteers steered a car along a virtual winding road
using either a computer mouse or a computer trackball. The virtual car
maintained a constant, moderate speed. Drivers encountered no
intersections, hazards or other vehicles. Still, simulated driving
while lying down in a noisy brain scanner proved challenging for
participants.

Undisturbed driving activated areas toward the back of the brain
involved in spatial perception.

In a second trial, participants steered a car down a virtual road with
one hand while listening to general-knowledge sentences that they had
to identify as true or false by pressing response buttons with the
other hand.

Drivers responded correctly to nearly all sentences. This verbal task
prompted strong activity in midbrain structures necessary for language
comprehension, as well as a 37 percent decline in activity in spatial
regions that had been employed during undisturbed driving.

During one-minute virtual trips, participants listening to sentences
drove onto the shoulder of the pavement or into the wrong lane 13
times on average, compared with 9 times on average for undisturbed
drivers.

“Listening to talk radio or to spoken directions from a navigation
system while driving probably have similar effects to what we found,”
Just says. “Multitasking puts high demands on the brain.”

http://www.sciencenews.org/view/generic/id/31426/title/Shifting_priorities_at_the_wheel
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