Discusses the work of psychologist Harold Pashler with split-brain
patients, as described in 'Neuroreport' (Vol. 5, No. 17). His theory
that, because of a bottleneck in our brain, it is difficult to perform
simultaneous tasks; Suggestion that the bottleneck occurs in the brain's
more primitive regions.
By
PT Staff, published on May 01, 1995
The chronically uncoordinated have long endured taunts about their
allegedinability to walk and chew gum simultaneously. But put the jokes
on hold: Psychologists say that doing two things at the same time can be
much harder than we think.
That's true even when the tasks are simple, says University of
California at San Diego psychologist Harold Pashler, Ph,D. A three
year-old might be able to perform either task alone. But because of a
bottleneck in our brain, even a Nobel Prize winner can't do them
simultaneously.
The major hurdle, apparently, lies in the brain's decision-making
and memory-retrieval systems. When simultaneous tasks both require us to
make a choice or summon a memory, a mental traffic jam occurs. The second
decision must await completion of the first (although we can act on the
first decision while making the second).
Pasher's work with split-brain patients, described in Neuroreport
(Vol. 5, No. 17), suggests the bottleneck occurs in the brain's more
primitive regions. In these patients the corpus callosum, a bundle of
fibers that relays information between the two cerebral hemispheres, is
severed. Yet when the patients attempted simultaneous tasks tailored to
involve different hemispheres, interference still occurred.
Even when we seem to be performing two tasks at once, often we are
really switching rapidly between them. That's why we can talk while
driving. "If you need to take half a second to decide where to steer,
your short-term memory holds on to your conversation," says Pashler. Your
brain switches gears like an English roadster, shifting back to the
discussion so smoothly that you don't notice the interruption. If,
however, you need to slam on the brakes to make an unexpected turn,
conversation also comes to a screeching halt while you decide what to do
next.
