Abstract
Visual context influences the ability to process object shape (shape constancy) but can also hinder performance on tasks that require judgments of apparent object shape where an individual must rely on the retinal image of a target. Participants completed a shape judgment task including judgments of projective (apparent) and objective (actual) shape for figures with varying amounts of context, defined as inclusion of 3-D information in the form of additional sides of a polyhedron. In the first study, participants completed judgments on figures with three levels of context: context-absent (only the target face present), context-partial (target face and a portion of additional top and side faces visible), and context-full (complete 3-D shape). In the second study, objective and projective judgments were completed on the same context-absent and context-full figures as well as two additional sets of images where one face of a complete polyhedral shape was missing. Shape judgments were less accurate when projective decisions were made in conditions including context (partial, single face missing, and full context) and when objective decisions were made in conditions lacking full context (absent, partial, single face missing). As the amount of context decreased, errors increased in objective judgments but decreased in projective judgments. Degree of rotation moderates the effects of context such that overall error increases with greater rotation of the target face and illustrates the important influence of level of context on shape judgment, where the most accurate judgments of actual shape require complete 3-D context while this same level of context distorts apparent judgments which benefit from an absence of context.