When you think about thinking, you probably focus most often
on your ability to make decisions or solve complex problems. An important part of your thinking abilities,
though, is the ability to predict what is going to happen in the future.
Some of those predictions involve sequences that are
predictable. Anyone who has listened to
a CD (or record, cassette, or 8-track) often knows that you start to hear the
first few notes of the next song on the album after a song ends. Even though you did not try to learn what was
coming next, your brain naturally helps you to make this prediction.
Other predictions involve actions. When you press down on the turn signal in
your car to make a left turn, you expect to hear the repeated click of the turn
signal. If you don’t hear the sound
after you engage the turn signal, you might look at the dashboard to make sure
that the turn signal is actually on. You
are able to do this, because you have made a mental connection between an
action and an outcome.
One question of interest to researchers was whether people
could also learn to predict what would happen when they made the choice not to
act. One the one hand, choosing not to
do something is still a choice, and so there is some information about that
decision in the brain that could be used as the basis of the prediction. On the other hand, choosing not to act means
that there is no information about a specific action that could be used to help
the brain predict what is going to happen.
The problem with studying a question like this is that you
need to have something to measure.
Traditional measurements in psychology involve actions, which makes it
hard to study what people do when they are choosing not to act.
To address this problem, Simone Kuhn and Marcel Brass turned
to brain imaging in a study published in the December, 2010 issue of Cognitive, Affective, and Behavioral
Neurosciences.
In this paper the researchers first trained people about
what would happen both when they acted and when they did not act. In this study, people sat in front of a
computer. Periodically, an orange dot
would flash on the screen. When this
happened, people had to make the choice either to press buttons in front of
them with each hand or not to press the buttons. (People were asked to use both hands because
that would ease the interpretation of the later part of the experiment in which
images of their brains were taken.) The
participants were asked to press the button on about half the trials, but to
make the choice as randomly as possible.
In this training part of the study, every time participants pressed the
buttons, they heard a high tone as feedback.
Every time they chose not to press the button, they heard a low tone as
feedback.
After this training, people were put in an fMRI
scanner. The scanner allows researchers
to measure changes in blood flow to different parts of the brain over
time. Because areas of the brain that
are active require a lot of energy, lots of blood will flow to regions that are
very active when a particular task is being performed. This blood flow brings the nutrients needed
for the brain to stay active.
After being put in the scanner, people did three different
tasks. In one task, they saw the same
orange dot, and they had to decide (as before) whether to respond or not. This time, though, no tone was played as
feedback. In another part of the study,
people saw either a red dot or a yellow dot.
When they saw the red dot, they had to press the button. When they saw the yellow dot, they had to
avoid pressing the button. Again, they
received no feedback. In the last task,
they just listened to tones.
The researchers first confirmed that when people listened to
tones, that the areas of their brain that normally respond to tones (the auditory cortex) would show increased
blood flow. Then, they looked at what
happened in auditory cortex in the other tasks.
When people pressed the button in response to the red dot, then auditory
cortex was also active, but when people did not act in response to the yellow
dot, auditory cortex was not active.
This result shows that when people are responding based on some event in
the world, then they do not predict what might have happened if they did not
respond.
The interesting result came when people chose either to
respond or not to respond to the orange dot.
In this case, auditory cortex was active both when people decided to
respond and when they did not. That is,
the practice session of the experiment led people to predict that when they
chose not to respond that they would hear a tone.
There are a few interesting aspects to these findings.
On the scientific side, these results demonstrate how brain
imaging can be used to study something that would be difficult to study
otherwise. It is hard to get people to
state reliably whether they are imagining a particular sound. Having a more objective measure (like
activity in the brain) helps to measure things that would be hard to detect
otherwise.
On the practical side, these findings show that your brain
treats your choice not to respond to something as if it was an action. That is useful. There are many situations in life where the
right thing to do is to refrain from acting in a situation. If someone cuts you off on the road, for
example, then it is a healthy thing not to yell at them or to make some kind of
gesture. Happily, your brain has
mechanisms in it that allow you to make good predictions about what will happen
in those situations when you choose not to act.
