This chapter deals with human perception and the diﬀerent ways in which
graphics and images are seen and interpreted. The early approach to the
study of perception focused on the vision system and its capabilities. Later
approaches looked at cognitive issues and recognition. We discuss each ap-
proach in turn and provide details. Signiﬁcant parts of this chapter, in-
cluding many of the ﬁgures, are based on the work of Christopher G. Healey
(http://www.csc.ncsu.edu/faculty/healey/PP/index.html) , who has
kindly granted permission for their reuse in this book.