Making Decisions Tires Your Brain

How Making Decisions Tires Your Brain

The brain is like a muscle: when it gets depleted, it becomes less effective.

By On Amir / Scientific American
July 22, 2008

brainpower.jpgThe human mind is a remarkable device. Nevertheless, it is not
without limits. Recently, a growing body of research has focused on a
particular mental limitation, which has to do with our ability to use a
mental trait known as executive function. When you focus on
a specific task for an extended period of time or choose to eat a salad
instead of a piece of cake, you are flexing your executive function
muscles. Both thought processes require conscious effort-you have to
resist the temptation to let your mind wander or to indulge in the
sweet dessert. It turns out, however, that use of executive function—a
talent we all rely on throughout the day—draws upon a single resource
of limited capacity
in the brain. When this resource is exhausted by one activity, our
mental capacity may be severely hindered in another, seemingly
unrelated activity. (See here and here.)

Imagine, for a moment, that you are facing a very difficult decision
about which of two job offers to accept. One position offers good pay
and job security, but is pretty mundane, whereas the other job is
really interesting and offers reasonable pay, but has questionable job
security. Clearly you can go about resolving this dilemma
in many ways. Few people, however, would say that your decision should
be affected or influenced by whether or not you resisted the urge to
eat cookies prior to contemplating the job offers. A decade of
psychology research suggests otherwise. Unrelated activities that tax
the executive function have important lingering effects, and may
disrupt your ability to make such an important decision. In other
words, you might choose the wrong job because you didn’t eat a cookie.

Taxing Tasks

But what types of actions exhaust executive function and affect
subsequent decision-making? Until recently, researchers focused on
activities that involved the exertion of self-control or the regulation
of attention. For instance, it’s long been recognized that strenuous
cognitive tasks—such as taking the SAT—can make it harder to focus
later on. But recent results suggests that these taxing mental
activities may be much broader in scope-and may even involve the very
common activity of making choices itself. In a series of experiments
and field studies, University of Minnesota psychologist Kathleen Vohs
and colleagues repeatedly demonstrate
that the mere act of making a selection may deplete executive
resources. For example, in one study the researchers found that
participants who made more choices in a mall were less likely to
persist and do well in solving simple algebra problems. In another task
in the same study, students who had to mark preferences about the
courses they would take to satisfy their degree requirements were much
more likely to procrastinate on preparing for an important test.
Instead of studying, these "tired" minds engaged in distracting leisure

Why is making a determination so taxing? Evidence implicates two
important components: commitment and tradeoff resolution. The first is
predicated on the notion that committing to a given course requires
switching from a state of deliberation to one of implementation. In
other words, you have to make a transition from thinking about options
to actually following through on a decision. This switch, according to
Vohs, requires executive resources. In a parallel investigation, Yale
University professor Nathan Novemsky and his colleagues suggest that
the mere act of resolving tradeoffs may be depleting. For example, in
one study, the scientists show that people who had to rate the
attractiveness of different options were much less depleted than those
who had to actually make choices between the very same options.

Choosy about Choices

These findings have important real world implications. If making
choices depletes executive resources, then "downstream" decisions might
be affected adversely when we are forced to choose with a fatigued
brain. Indeed, University of Maryland psychologist Anastasiya
Pocheptsova and colleagues found exactly this effect: individuals who
had to regulate their attention—which requires executive control—made
significantly different choices
than people who did not. These different choices follow a very specific
pattern: they become reliant on more a more simplistic, and often
inferior, thought process, and can thus fall prey to perceptual decoys.
For example, in one experiment participants who were asked to ignore
interesting subtitles in an otherwise boring film clip were much more
likely to choose an option that stood next to a clearly inferior
"decoy"—an option that was similar to one of the good choices, but was
obviously not quite as good—than participants who watched the same clip
but were not asked to ignore anything. Presumably, trying to control
one’s attention and to ignore an interesting cue exhausted the limited
resource of the executive functions, making it significantly more
difficult to ignore the existence of the otherwise irrelevant inferior
decoy. Subjects with overtaxed brains made worse decisions.

These experimental insights suggest that the brain works like a muscle:
when depleted, it becomes less effective. Furthermore, we should take
this knowledge into account when making decisions. If we’ve just spent
lots of time focusing on a particular task, exercising self-control or
even if we’ve just made lots of seemingly minor choices, then we
probably shouldn’t try to make a major decision. These deleterious
carryover effects from a tired brain may have a strong shaping effect
on our lives.

book Proust was a Neuroscientist.


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