The new theoretical ideas and paradigms resulting from this resurgence in the study of visual memory are the focus of this special issue. While they were studying an image, scanning from one object to another, details of the scene were changed during a saccade. Furthermore, Grimes used photographs rather than simple novel objects or letters, thereby bringing demonstrations of change blindness closer to everyday perceptual experience. More recently, several labs have shown that change blindness for objects in natural scenes can occur during a fixation if the effects of a saccade are simulated by disrupting the retinal transient normally accompanying a change. In the flicker paradigm, an original and modified image are presented in rapid alternation with a blank screen between them.
Observers respond as soon as they detect the changing object.
In the forced choice detection paradigm, observers only receive one view of each scene before responding, so the total duration of exposure to the initial scene can be controlled more precisely. Furthermore, because only a subset of the images have changes, signal detection analyses can be used and both accuracy and latency can be used as dependent measures. Both the flicker paradigm and the forced choice detection paradigm are intentional change detection tasks in that observers know that changes will occur and actively search the display to find differences. This work demonstrates that observers are change blind even when their primary task is to search for change. Other change detection studies examine detection performance under divided attention conditions.