Attentional frames, frame curves and figural boundaries: the inside/outside dilemma

Attended and unattended regions of the image array are viewed often as binary complements to one another, with a well-defined boundary between them. A simple experiment shows otherwise: if the contour of a simple convex shape is perturbed to create a distinctive texture, it is typically the outside of the contour that provides the basis for similarity judgement, not the inside. The introduction of the appropriate task, however, can make the inside part of the contour become more salient. A similar result occurs for concave shapes, such as a C, where notions of containment are not easily specified. These observations suggest that figure boundaries are difficult to define objectively and that the setting of an attentional reference frame plays a key role in object description. We propose that this frame is part of a virtual, transparent blackboard or "clearboard", bound to the scene, not to the image.