Yesterday we discussed the link between autobiographical memory and visual imagery.  What, though, if you don’t have any skills for visualization?  We have known since the 1880s that there are individuals who look at you as if you’re crazy if you ask them to describe the pictures in their heads. William James considered that  “thought stuff,” as he called it, might consist in some people not so much of visual imagery as of imagery of other modes, especially the “verbal images” of inner speech. Galton did numerous experiments (not all of them replicable) that intended to show that scientists lacked visual imagery – this is too much of a generalization, but it turns out, indeed, that there are about 2% of the general population who cannot visualize images. For them the request to describe what they “see” with their minds’ eye is like asking you is March 19 black, orange or white. And there are higher proportions of scientists who excel at spatialization.

These days they call it Aphantasia and treat it as if it were a new discovery – http://www.nytimes.com/2015/06/23/science/aphantasia-minds-eye-blind.html

People without visual imagery are functioning perfectly well in the world, because there are alternatives, whether James’ inner speech or more commonly spatialization. When they are asked to think about an event while we scan their brain it is not the visual cortex that gets activated but the parietal areas of the brain that are in charge of spatial orientation. The congenitally blind  without a history of form vision are able to represent spatial relationships in dream experience without either visual imagery or compensatory imagery in other modalities. In other words, their dreams reflect the way they experience the world, in spatial, not visual terms.