A post by Thomas Naselaris

For most people, it feels right to talk about mental imagery as a kind of visual experience. However, few experience mental imagery as being exactly like seeing, and describing the ways in which mental imagery differs from seeing is challenging. It is a bit like trying to explain the style of a visual artist whose works have been displayed to you alone. If it were easy to convey a visual style with words, there would probably be nothing special about it.

One of the goals of empirical research on mental imagery should be to develop and name concepts that explain, rigorously and measurably, what makes mental images so different from seen ones, while making clear the connection between seeing and imagining. 

An important first stab at this is the characterization of mental imagery as “weak vision” (Pearson et al) . This characterization is certainly consistent with my subjective experience of imagery, which is weaker than my experience of seeing, and it is consistent with objective measurements of brain activity, which is indeed much weaker during imagery than vision (Breedlove et al).