“Recent research on change detection has documented surprising failures to detect visual changes occurring between views of scene, suggesting the possibility that visual representations contain few details. Although these studies convincingly demonstrate change blindness for objects in still images and motion pictures, they may not adequately assess the capacity to represent objects in the real world. Here we examine and reject the possibility that change blindness in previous studies resulted from passive viewing of 2-d displays… Furthermore, successful detection depended on social group membership; pedestrians from the same social group as the experimenters detected the change but those from a different social group did not. A second experiment further examined the importance of this effect of social group. Provided that the meaning of a scene is unchanged, changes to attended objects can escape detection even when they occur during a natural real-world interaction. The discussion provides a set of guidelines and suggestions for future research on change blindness……..
A more fundamental question involves assessing the similarity of the experimenters. Clearly no one would be surprised if pedestrians failed to notice a substitution of identically dressed identical twins. The inability to notice small changes is unsurprising because such changes naturally occur between views. For example, people rarely notice variation in the position and orientation of moveable objects such as the body parts. If we constantly noticed such changes, they would likely detract from our ability to focus on other, more important aspects of our visual world. Change detection as a method relies on the tendency of our visual system to assume an unchanging world. The fact that we do not expect one person to be replaced by another during an interaction may contribute to our inability to detect some changes. A critical question for future research is why some changes are more likely to be detected than others. Clearly we would be quite surprised if subjects missed a switch between enormously different people (e.g. a switch from a 4ft. 9 in. female to a 6ft 5 in. male of another). The change in this case would alter not only the visual details of a person, but also category membership. If, as suggested by other recent findings of change blindness, we retain only abstracted information and not visual details from one moment to the next, changes to category membership may well be detectable. Abstraction of category information is clearly central to coding other people and may underlie the representation of other objects across views as well.”
D.J. Simons & D.T. Levin, Failure to detect changes to people during a real- world interaction, Psychonomic Bulletin & Review, 1998, 5 (4)