Boundary extension: findings and theories

A view of a scene is often remembered as containing information that might have been present just beyond the actual boundaries of that view, and this is referred to as boundary extension. Characteristics of the view (e.g., scene or nonscene; close-up or wide-angle; whether objects are cropped, static, or in motion, emotionally neutral or emotionally charged), display (e.g., aperture shape and size; target duration; retention interval; whether probes of memory involve magnification/minification or change in physical distance), and observer (e.g., allocation of attention; age; planned fixation, gaze direction, and eye movements; monocular or binocular viewing; prior exposure; neurological correlates) that influence boundary extension are reviewed. Proposed mechanisms of boundary extension (perceptual, memory, or motion schema; extension-normalization; attentional selection; errors in source monitoring) are discussed, and possible relationships of boundary extension to other cognitive processes (e.g., representational momentum; remembered distance and remembered size; amodal completion; transsaccadic memory) are briefly addressed.