“When pigs fly”. A figure of speech we use to indicate the improbability of an event occurring. Benjamin Bergen, in his masterpiece on the new science of how the mind makes meaning, uses the graphic of the flying pig to illustrate how imagery interacts with vision. He refers to this as embodied simulation, a first cousin to embodied cognition. Bergen gets quite detailed about how individuals will use verbalization as opposed to visualization. Part of this resides in distinctions between dorsal and ventral stream function. Spatial visualizers tend to reason about the arrangement of objects in space and their motion – more in line with the Where pathway. Object visualizers are good at perceiving and recalling visual properties of objects themelves, as though they were relying more heavily on the What pathway.
Within verbalization there is a distinction between overt verbalization – when your lips move or you write something down, what we tend to describe as subvocalization – and covert verbalization – when there is verbal support to imagery is silent in our minds. We might consider this to be auditory imagery, and the parallels as well as interactions are something I touched upon in a recent OEP monograph. Elliot Forrest was, of course, the optometric dean of visual imagery, and John Abbondonza has done an excellent job of updating the subject in this PowerPoint presentation.
Bergen finishes the review of research from his Language & Cognition Lab at UCSD and other research on embodied cognition with a fascinating insight about math. It seems that when people are doing math, they use brain regions that also do spatial processing, and there is an asymmetry. People are faster to respond to larger numbers on the right side of their body and to smaller numbers on the left side. Further, when you ask people to select a number, they tend to look left when picking a low number and to the right when picking a larger number. This association of space with number has led some researchers to conclude that people think about number using a mental number line.
The most compelling evidence that doing math involves spatial cognition comes from patients with hemispatial neglect. Amazingly, people with hemispheric neglect also seem to have a sort of numerical neglect. If you ask them to say what number is exactly between 2 and 6, they will tend to shift their answer toward the non-neglected side. Someone with left neglect is more like to answer “5” than “4”. People seem to use some of the same brain circuitry to that allows them to perceive and act in space in order to make judgements about numbers.