Over thinking Can Be Detrimental to Human Performance
Trying to explain riding a bike is difficult because it is
an implicit memory. The body knows what to do, but thinking about the process
can often interfere. So why is it that under certain circumstances paying full
attention and trying hard can actually impede performance? A new UC Santa
Barbara study, published today in the Journal of Neuroscience, reveals part of
the answer.
There
are two kinds of memory: implicit, a form of long-term memory not requiring
conscious thought and expressed by means other than words; and explicit,
another kind of long-term memory formed consciously that can be described in
words. Scientists consider these distinct areas of function both
behaviorally and in the brain.
Long-term memory is supported by various regions in the
prefrontal cortex, the newest part of the brain in terms of evolution and the
part of the brain responsible for planning, executive function, and working
memory. "A lot of people think the reason we're human is because we have
the most advanced prefrontal cortex," said the study's lead author, Taraz
Lee, a postdoctoral scholar working in UCSB's Action Lab.
Two
previous brain studies have shown that taxing explicit memory resources
improved recognition memory without awareness. The
results suggest that implicit perceptual memory can aid performance on
recognition tests. So Lee and his colleagues decided to test whether the
effects of the attentional control processes associated with explicit memory
could directly interfere with implicit memory.
Lee's study used continuous theta-burst transcranial
magnetic stimulation (TMS) to temporarily disrupt the function of two different
parts of the prefrontal cortex, the dorsolateral and ventrolateral. The dorsal
and ventral regions are close to each other but have slightly different
functions. Disrupting function in two distinct areas provided a direct causal
test of whether explicit memory processing exerts control over sensory
resources -- in this case, visual information processing -- and in doing so
indirectly harms implicit memory processes.
Participants
were shown a series of kaleidoscopic images for about a minute, then
had a one-minute break before being given memory tests containing two different
kaleidoscopic images. They were then asked to distinguish images they had seen
previously from the new ones. "After they gave us that answer, we asked
whether they remembered a lot of rich details, whether they had a vague
impression, or whether they were blindly guessing," explains Lee.
"And the participants only did better when they said they were
guessing."
The results of disrupting the function of the dorsolateral
prefrontal cortex shed light on why paying attention can be a distraction and
affect performance outcomes. "If we
ramped down activity in the dorsolateral prefrontal cortex, people remembered
the images better," said Lee.
When the researchers disrupted the ventral area of the
prefrontal cortex, participants' memory was just slightly worse. "They
would shift from saying that they could remember a lot of rich details about
the image to being vaguely familiar with the images," Lee said. "It
didn't actually make them better at the task."
Lee's fascination with the effect of attentional processes
on memory stems from his extensive sports background. As he pointed out, there
are always examples of professional golfers who have the lead on the 18th hole,
but when it comes down to one easy shot, they fall apart. "That should be
the time when it all comes out the best, but you just can't think about that
sort of thing," he said. "It just doesn't help you."
His continuing studies at UCSB's Action Lab will focus on
dissecting the process of choking under pressure. Lee's work will use brain
scans to examine why people who are highly incentivized to do well often
succumb to pressure and how the prefrontal cortex and these attentional
processes interfere with performance.
"I
think most researchers who look at prefrontal cortex function are trying to
figure out what it does to help you and how that explains how the brain works
and how we act," said Lee. "I look at it at the opposite.
If we can figure out the ways in which activity in this part of the brain hurts
you, then this also informs how your brain works and can give us some clues to
what's actually going on."
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