We use lots of mental images to help us plan actions. I remember times when I helped friends move
from one apartment to another. The
trickiest part of these moves was getting the couch out of the living room and
outside onto a truck. Yet, we often
managed to do it successfully by first imagining how to position the couch to
get it through narrow hallways and out of awkwardly placed doors.
The importance of this kind of imagery for performing
actions in the world leads to questions about whether the ease of acting in the
world affects the ease of manipulating your mental images. This question was addressed in a paper by
Stephen Flusberg and Lera Boroditsky in the February, 2011 issue of Psychonomic Bulletin and Review.
These authors did a clever study using a version of a mental
rotation experiment first done in the 1970s.
In the original mental rotation studies, people saw three-dimensional
figures like the ones in the Figure shown here.
Sometimes people saw two identical objects, while sometimes the objects
were mirror images of each other. They
had to judge whether the objects were the same.
As shown in the figure, the objects could appear in
different rotations relative to each other.
The classic finding of these studies is that the larger the degree of
rotation between the objects, the longer it takes people to respond whether
they are identical. These results
suggest that people are mentally rotating an image of the objects until they
are aligned so that they can judge whether they are identical.
Flusberg and Boroditsky had people play with the objects
before doing the mental rotation task.
They built wooden versions of the figures. Some of them were painted red and others were
painted blue. The figures were attached
to an axle that was set in a can. They
acted as a handle on the axles. The cans
were set up so that some of them had sand in them, so that they were hard to
turn, while others were empty and were easy to turn.
At the start of the study, participants were asked to turn
the handles. For each of the
participants, one color was hard to turn and the other was easy. For example, the red handles might be
difficult to turn, and the blue ones easy.
After this experience with the physical handles people did a
mental rotation study. Participants saw
pairs of pictures and judged whether the objects were identical, just as in the
classic study. There were two big
differences from the previous work.
First, half of the objects were blue and half were red. Second, half the participants were told to
imagine physically moving the objects until they were aligned, while the other
half were told just to imagine the objects moving on their own.
The group that was told to imagine the objects moving on
their own showed the classic mental rotation effect, but no effect of the color
of the objects. That is, it took longer
to make the judgment as the objects were rotated further from each other. But, people’s previous experience with the
objects had no effect on this mental rotation.
The group that was told to imagine moving the objects showed
both the classic mental rotation effect and an effect of the color of the
objects. That is, those objects that
were the same color as the ones that were harder to move were mentally rotated
more slowly than those that were the same color as the ones that were easier to
move.
These results demonstrate the close linkage between action
and imagery. When an object is hard to
move, it is also hard to imagine moving it.
Why would our ability to move objects affect our
images?
In order to solve problems like moving a couch, we need to
bring to bear both our knowledge of the geometry of the object as well as our
knowledge of our own physical abilities.
It would not be useful to envision ways of moving an object that we
could not carry out physically. So,
incorporating both visual aspects of objects and movement makes your ability to
plan more efficient, because you do not consider many possibilities that would
be physically impossible to perform.
