Boundary Extension

Boundary extension is a cognitive psychology phenomenon in which a person remembers having seen more of a scene, extending beyond its original edges, than was actually shown in the picture or scene they originally viewed, an error of commission in visual memory. Researchers typically study the effect using recognition memory tasks in which participants view close-up or wide-angle photographs during a study phase and then judge whether photographs shown at test, which may have an expanded or identical field of view, match what they originally saw; participants tend to mistakenly accept photographs with an expanded background as matching, revealing that their memory representation had already extended the scene's boundaries. The effect has been demonstrated across many kinds of visual material, across age groups from infancy through old age, in people with neurological differences such as Down syndrome, and in senses beyond vision, including touch and hearing, and it is generally attributed to some combination of source-monitoring errors and the influence of prior perceptual expectations on how a scene is mentally represented.