 Though imagery has played an important role in the history of philosophy of mind, the important contemporary literature on it is primarily psychological. (Tye 1991 and McGinn 2004 are notable recent exceptions.) In a series of psychological experiments done in the 1970s (summarized in Kosslyn 1980 and Shepard and Cooper 1982), subjects’ response time in tasks involving mental manipulation and examination of presented figures was found to vary in proportion to the spatial properties (size, orientation, etc.) of the figures presented. The question of how these experimental results are to be explained kindled a lively debate on the nature of imagery and imagination.