The cognitive neuroscience of mental imagery.

This special issue is devoted to recent work on mental imagery. To get a sense for the subject matter, answer the following questions: How many windows are there in your living room? What socks did you wear yesterday? Is there room in your refrigerator for a litre of milk? These questions typically evoke visual mental imagery. For example, when answering the first, people usually visualize the room, and then 'scan' over each wall, 'seeing' each window with their mind's eye. Similarly, if asked whether a cat's meow has a higher pitch than the sound of a blender, most people report 'hearing' the sounds in their 'mind's ear'. Such tasks evoke auditory mental imagery. Visual mental imagery is 'seeing' in the absence of the appropriate immediate sensory input, auditory mental imagery is 'hearing' in the absence of the appropriate immediate sensory input, and so on. Imagery is distinct from perception, which is the registration of physically present stimuli. The examples illustrate that imagery plays an important role in memory and spatial reasoning, but as we shall see, these functions merely scratch the surface. Imagery also plays a role in abstract reasoning, skill learning, and language comprehension. One of the major insights about imagery is that----even within a single sensory modal i ty l i t is not a single, undifferentiated ability. Rather, as the opening example suggests, imagery involves a host of processes working together. The image of one's living room must be formed at the outset, it then must be scanned and interpreted, and must be maintained while this is occurring. Moreover, in many situations the imaged object must be transformed. For example, when asked whether frogs have stubby green tails, people often report 'mentally rotating' the amphibian and 'looking' at its posterior quarters. Interest in mental imagery has waxed and waned for centuries, and is now undergoing a resurgence. Unlike previous periods of enthusiasm for the topic, the present one is not driven by philosophical concerns or claims based on introspection. Rather, the present