Language is our most powerful tool
for thinking. We talk to other people to
solve problems, and we also use internal monologues to guide our thinking. However, there are some things that language
is not so good at. One particular
limitation of language is in describing and manipulating three-dimensional
space. For example, when you want to
describe the size of an object, you often resort to comparing an object to
something of known size (“That dog was the size of a small car!”) or using
gestures to indicate sizes.
Movements of your hands and arms
seem particularly well-suited to thinking about space. We have to configure our hands to grasp
objects, and so we must have ways to represent sizes in order to plan those
movements. In addition, the movements
themselves provide a method for changing the location objects and their
orientation. In a store, the price of
many objects is printed on the bottom, and so you just pick up the object and
turn it over, effortlessly exposing the bottom.
Does this ability to move objects
around also help you to think about the movements of objects that aren’t
physically present? This question was
addressed in a paper in the February, 2011 issue of the Journal of Experimental Psychology: General by Mingyuan Chu and
Sotaro Kita.
These researchers examined
people’s performance in a mental rotation task.
In mental rotation, people see pictures of two objects. The objects are either identical or one is the
mirror image of the other. In addition,
the objects are rotated through some angle so that they are each in a different
orientation. Examples of the figures
used in studies like this are in the figure.
The top row shows a pair of identical objects at a moderate degree of rotation. The bottom row shows objects that are mirror
images.
Studies of mental rotation started
with the work of Roger Shepard and his students in the 1970s. Participants are asked to press a button as
soon as they know whether the objects are identical or are mirror images. The classic finding of this work is that as
the difference in angle of rotation between the two objects increases, people
take longer to respond and they make more errors. This pattern of findings suggests that people
may be mentally rotating the objects to place them in the same mental
orientation in order to compare them.
In one study, Chu
and Kita used this mental rotation task and told people they could take as much
time as they needed to solve the problems.
They looked at whether people spontaneously made hand movements in which
they rotated their hands as if they were rotating the objects. In this study, people were far more likely to
make rotating hand movements when there was a big difference in orientation
between the objects than when there was a small difference in orientation. That is, when the problems got difficult,
people seemed to use hand movements to help them rotate an object that wasn’t
actually there.
In a second study, participants
were either explicitly encouraged to use gestures or they were forbidden to use
gestures. In the case where people were
forbidden to use gestures, they had to sit on their hands. In this case, people made many fewer errors
in their judgments when they were allowed to gesture than when they were not.
Why do gestures help you imagine
rotations?
Because you often use your arms
and hands to change the position of objects in space, your visual system has a
lot of experience witnessing these changes in position when you make particular
kinds of movements. You have picked up
lots of objects and turned them over, and so there is a strong association
between these movements and the changes in what you can see in the world. This close connection between body movements
and the state of the world may come to influence your mental images as
well. Turning your hands in a particular
direction supports thinking about the object moving in that direction, because
these turning movements often led to movements of objects in that direction in
the past.
That means that when you are
trying to solve a difficult spatial problem, it is a good idea to give yourself
room to move around. These movements may
actually help you think about space and movements through space more easily.
