"We must begin by distinguishing between visual mental imagery and visual perception: Visual perception occurs while a stimulus is being viewed, and includes functions such as visual recognition and identification . Two types of mechanisms are used in visual perception: “bottom-up” mechanisms are driven by the input from the eyes; in contrast, “top-down” mechanisms make use of stored information . Visual mental imagery is a set of representations that gives rise to the experience of viewing a stimulus in the absence of appropriate sensory input. In this case, information in memory underlies the internal events that produce the experience. Unlike afterimages, mental images are relatively prolonged."

“Even if it were clear what was meant, this sort of treatment would seem closer to describing what is taking place than to explaining it. I do not want to deny the value of describing a phenomenon; rich descriptions facilitate theorizing, and there is no more astute observer than Piaget. But in my view explanations of cognitive phenomena should specify the ways in which functional capacities operate. Piaget and Inhelder’s account is more on the level of intentionality, and hence is open to multiple interpretations at the level of the function of the brain. The do not specify how interiorized imitation operates, nor have they specified the format or content of the image. This level of discourse will never produce process adequacy, and hence seems of limited value.”

“Mr. Magoo Rule: Text and graphics must be easily distinguished and recognized. Don ́t make your audience members feel like the vision challenged Mr. Magoo—viewers of an electronic slideshow should not risk eyestrain!”

“But because of the way in which depictions represent, there is a correspondence between parts and spatial relations of the representation and those of the object; this structural mapping, which confers a type of resemblance, underlies the way images convey specific content. In this respect images are like pictures. Unlike words and symbols, depictions are not arbitrarily paired with what they represent.”

“Bullets are a convenient way to present the separate elements of a list. However, bullets are a bit like salt—often essential to bring out the best, but distasteful if overdone.”

“It is hard to define something one knows little about”

“Physics seems to have done reasonably well in studying electrons, although there is not to this day a precise definition of this term.”