August 5, 2001Contact: Public Affairs Office(202) 336-5700 firstname.lastname@example.org
MULTITASKING MORE EFFICIENT? SHIFTING MENTAL GEARS COSTS TIME,
ESPECIALLY WHEN SHIFTING TO LESS FAMILIAR TASKS
The "Inner CEO" Can Improve Interface Design, Personnel
Training And Diagnosis Of Brain Damage
- New scientific studies reveal the hidden costs of multitasking,
key findings as technology increasingly tempts people to do more
than one thing (and increasingly, more than one complicated thing)
at a time. Joshua Rubinstein, Ph.D., of the Federal Aviation Administration,
and David Meyer, Ph.D., and Jeffrey Evans, Ph.D., both at the
University of Michigan, describe their research in the August
issue of the Journal of Experimental Psychology: Human Perception
and Performance, published by the American Psychological Association
Whether people toggle between browsing the Web and using other
computer programs, talk on cell phones while driving, pilot jumbo
jets or monitor air traffic, they're using their "executive
control" processes -- the mental CEO -- found to be associated
with the brain's prefrontal cortex and other key neural regions
such as the parietal cortex. These interrelated cognitive processes
establish priorities among tasks and allocate the mind's resources
to them. "For each aspect of human performance -- perceiving,
thinking and acting -- people have specific mental resources whose
effective use requires supervision through executive mental control,"
better understand executive control, as well as the human capacity
for multitasking and its limitations, Rubinstein, Meyer and Evans
studied patterns in the amounts of time lost when people switched
repeatedly between two tasks of varying complexity and familiarity.
In four experiments, young adult subjects (in turn, 12, 36, 36
and 24 in number) switched between different tasks, such as solving
math problems or classifying geometric objects. The researchers
measured subjects' speed of performance as a function of whether
the successive tasks were familiar or unfamiliar, and whether
the rules for performing them were simple or complex.
measurements revealed that for all types of tasks, subjects lost
time when they had to switch from one task to another, and time
costs increased with the complexity of the tasks, so it took significantly
longer to switch between more complex tasks. Time costs also were
greater when subjects switched to tasks that were relatively unfamiliar.
They got "up to speed" faster when they switched to
tasks they knew better, an observation that may lead to interfaces
designed to help overcome people's innate cognitive limitations.
researchers say their results suggest that executive control involves
two distinct, complementary stages: goal shifting ("I want
to do this now instead of that") and rule activation ("I'm
turning off the rules for that and turning on the rules for this").
Both stages help people unconsciously switch between tasks.Rule
activation itself takes significant amounts of time, several tenths
of a second -- which can add up when people switch back and forth
repeatedly between tasks. Thus, multitasking may seem more efficient
on the surface, but may actually take more time in the end. According
to the authors, this insight into executive control may help people
choose strategies that maximize their efficiency when multitasking.
The insight may also weigh against multitasking. For example,
Meyer points out, a mere half second of time lost to task switching
can mean the difference between life and death for a driver using
a cell phone, because during the time that the car is not totally
under control, it can travel far enough to crash into obstacles
the driver might have otherwise avoided.
executive mental control may help solve "fundamental problems,"
says Meyer, "associated with the design of equipment and
human-computer interfaces for vehicle and aircraft operation,
air traffic control, and many other activities in which people
must monitor and manipulate the environment through technologically
advanced devices." The research may also aid in personnel
selection (given individual differences in executive control),
training, assessment and diagnosis of brain-damaged patients (given
advances in brain imaging and mapping), rehabilitation, and formulation
of government and industrial regulations and standards. In addition,
results from the study of executive control may foster a more
general understanding of how the brain and human consciousness
"Executive Control of Cognitive Processes in Task Switching,"
Joshua S. Rubinstein, U.S. Federal Aviation Administration, Atlantic
City, N.J.; David E. Meyer and Jeffrey E. Evans, University of
Michigan, Ann Arbor, Mich., Journal of Experimental Psychology
- Human Perception and Performance, Vol 27. No.4
Rubinstein can be reached by phone at (609) 485-4463 or electronically
at Josh.Rubinstein@tc.faa.gov. David Meyer can be reached by phone
at (734) 763-1477 or electronically at email@example.com.
text of the article is available from the APA Public Affairs Office
and at http://www.apa.org/journals/xhp/press_releases/august_2001/xhp274763.html.
American Psychological Association (APA), in Washington, DC, is
the largest scientific and professional organization representing
psychology in the United States and is the world's largest association
of psychologists. APA's membership includes more than 155,000
researchers, educators, clinicians, consultants and students.
Through its divisions in 53 divisions of psychology and affiliations
with 60 state, territorial and Canadian provincial associations,
APA works to advance psychology as a science, as a profession
and as a means of promoting human welfare.
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