Sigrid Leyssen's project had two protagonists: a series of well-preserved paper discs that carry precisely measured curved lines, mostly in red and black; and the experimental psychologist Albert Michotte (1881–1965). The discs are part of a little-known moving image machine, used to present abstract moving stimuli images to experimental subjects. These images were created and used from the late 1930s through the 1960s in the psychological laboratory of Michotte in Louvain, Belgium. They served for studying the perception of causality and many related impressions, such as the tool effect, the tunnel effect, or the impression of animacy. These studies were part of Michotte’s experimental phenomenology of perception.
These rotating discs and the abstract moving images they produced were taken as a starting point to study the history of stimuli images in the psychology of perception. Sigrid Leyssen investigated how such images, used as stimulation for the study of perception, and have come to take their particular forms and functions. It is a history that reveals stimuli images as complex creations that both reflect and construct different understandings of perception and cognition, of psychological observation, and of more general daily practices of perceiving, such as watching moving images in different media.