Are things that are hard to physically move also hard to imagine moving?
Flusberg, S. J., & Boroditsky, L. (2011). Are things that are hard to physically move also hard to imagine moving? Psychonomic Bulletin And Review, 18(1), 158–164. doi:10.3758/s13423-010-0024-2
Summary
Flusberg & Boroditsky begin with the following important question (pg. 158-159):
On the one hand, there appear to be tight links among perception, action and mental imagery, both in behavior and in the underlying neural circuitry… On the other hand, what often seems to separate our imagination from the everyday world is that it appears free from the constraints imposed by the physical environment. Indeed, people often imagine actions or events that they have never seen or never could experience themselves… to what extent do our experiences with objects in the real world impinge on our ability to represent and manipulate those objects in mental imagery?
To get at this question, they perform the classic mental rotation task but prime participants first by having them physically rotate the objects. The key manipulation was that some of the objects were more difficult to physically rotate than the others (denoted by color). Flusberg & Boroditsky found that participants had longer response times when using motor imagery after performing the physical rotations (whereas there was no effect when using visual imagery), and also that there was an effect of the angle of rotation on the difficulty of rotation (i.e. the slope for the more difficult objects was higher than that for the less difficult objects, which is what would be expected from manually performing the rotations). However, they only saw this effect after excluding some of the participants post-hoc.
Takeaways
I think this is a cool study, though I would have liked to see a more in depth evaluation—for example, more angles of rotation, and more than two levels of difficulty. I also think it would have been better to have participants do the mental rotation task on entirely different objects than the ones they physically rotated, because it’s not clear to me whether they measured an effect of prior knowledge (i.e. abstract knowledge about the difficulty of manipulating the object) or an effect of prior experience (i.e. they are just replaying an experience they had). I would be inclined to believe they actually are measuring prior knowledge (as they claim), but I would like to know for sure.
Methodology aside, the fact that there is a difference between motor imagery and visual imagery is quite interesting. I want to know why this difference exists, though; I’m not convinced there is actually a hard line that can be drawn between the two. Typically, tasks like mental rotation do still involve some amount of motor activation in the brain, meaning that motor imagery isn’t entirely separate from visual imagery. Perhaps the distinction shouldn’t be between motor/visual, but just based on the mechanism by which the object is moving (or, put another way, how the simulated scene is constructed). If you are asked to imagine moving it yourself, then it makes sense that you would imagine what the effects of your motor actions are. If you are asked to imagine the object itself moving, then it perhaps you are imagining (for example) the object sitting on a rotating disk. It would be interesting to try to come up with a task that would require the “visual imagery” condition to still engage in some sort of motor imagery, but motor imager that is irrelevant to how difficult the object is to move. Would that cause an effect of difficulty to appear in the visual imagery condition? I hypothesize that it wouldn’t, which would imply that the distinction isn’t between motor and visual imagery but in terms of how the simulation is constructed, somehow.