Mental Manipulation Limitations

“I draw to clarify things to others and in my mind. So I can see the relationships between things.” - Survey #26

In his 2003 book, Seeing and Visualizing: It’s Not What You Think, cognitive scientist Zenon Pylyshyn discusses this and other limitations of our mental capacities in imagining visual information and proposes arguments for why the use of drawing is essential for understanding our own mental images as well as overcoming these limitations. “It is widely held that one of the purposes of mental images is to allow us to discover new visual properties or see new visual interpretations or reconstruals in imaginally presented information,” he states. Pylyshyn goes on to point out that this theory is valid only to a certain degree, that once we begin to manipulate the images in our head our ability to maintain the “whole picture” diminishes. He warns: 

“Our mental image also does not have the benefit of being a rigid surface, so it does not have the stability and invariance of properties that a physical picture has when various operations are applied to it. For example, unlike a physical diagram, a mental image does not automatically retain its rigid shape when we transform it say, by rotating it, moving its parts around, folding it over, or adding new elements to it. This is because there is no inner drawing surface to give a mental image its rigidity and enduring shape and because there is no credible evidence for visually ‘noticing’ new patterns or new construals in an image”|Pylyshyn, 2003|.

This notion may be disagreeable to those who believe their mental capacities to be quite advanced, but these observations are not intended as an attack on personal intelligence; this viewpoint reflects the large body of research focused on how our cognitive systems work, and it has been shown that our abilities to manipulate mental images are not nearly as powerful as we would assume them to be. Jonathan Fish and Stephen Scrivener, of the University of Technology in Leicestershire, U.K., agree that mental images can be manipulated with more speed and flexibility than visual percepts, but their evidence shows that our working memory and attention have low spatial capacity and short duration |Fish, 1990|.

Turning our ideas into drawings allows other visual processes such as spatial relationship detection and pattern recognition to take place subconsciously.

The following is a quick, two part test. In the first part we are only allowed to use mental images to solve the puzzle: imagine a cube (you may determine the size); if you were to hold that cube so that the index finger of each hand was in contact with opposing corners of the cube, how many corners are left untouched? Now let’s cut that cube in half (for the purposes of this exercise, there is no gravity to cause the cube to fall to the floor) — how many new corners have we just created? And suppose we take one half of the cube and cut it in half again? How many corners are there in total for the entire cube? Now, for the second part of the test, use a piece of paper and a writing tool to retake the test.

(Hover to show answer)

fig. 15. a visual representation of the cube-slicing test. With the visual representation, we are able to hold the “big picture” as well as each new modification of the cube.

Were your answers the same for both methods? Was your answer 22? (see fig. 15 on the following page as an example)

What we learn from this simple test forms one of the strongest arguments for using drawing to solve problems: there is a point at which we reach the limitations of our mental manipulation capacities and we must rely on the inherent abilities of our visual system to reveal opportunities for reaching solutions.