Visual imagery, seeing in the absence of a visual stimulus. Mental imagery, ability to recreate the sensory world in the absence of physical stimuli. Wundt proposed that images were one of the three basic elements of consciousness (along with sensations and feelings) Because images accompany thought, studying images was a way of studying thinking. Imageless thought debate, thought is impossible without an image. Francis galton (1883) observed that people who had great difficulty forming visual images were still quite capable of thinking. Introduction of behaviouralism, believed study of imagery as unproductive, visual images are invisible to everyone except the person experiencing them. Development of ways to measure behaviour that could be used to infer cognitive processes. Participants are presented with pairs of words during a study period. During the test period, they are presented with the first word from each pair. Task is to recall the word that was paired with it during the study period.