Figure 9.3 Overlapping forms used in an experiment on attention To assess the degree to which vision can be selective, Rock and Gutman (1981) directed subjects to attend to either just the red or just the green shape in images such as this and then tested their recognition of both shapes in each image.
(From Rock, I., & Gutman, D. (1981). The effect of inattention on form perception. Journal of Experimental Psychology: Human Perception and Performance, 7, 275-285. Figure 1, p. 276. Copyright © American Psychological Association.)