In W. Banks (ed). Encyclopedia of Consciousness. Vol 1. New York: Elsevier. pp. 47-59. 2009 [pdf]
Change blindness (CB) refers to the failure of an observer to visually experience changes that are easily seen once noticed. This can happen even if the changes are large, constantly repeat, and the observer has been informed that they will occur. A related phenomenon is inattentional blindness (IB), the failure to visually experience an object or event when attention is directed elsewhere. For example, an observer may fail to notice an unexpected object that enters their visual field, even if this object is large, appears for several seconds, and has important consequences for the selection of action.
Both phenomena involve a striking failure to report an object or event that is easily seen once noticed. As such, both are highly counterintuitive, not only in the subjective sense that observers have difficulty believing they could fail so badly at seeing, but also in the objective sense that these findings challenge many existing ideas about how we see. But as counterintuitive as these phenomena are, progress has been made in understanding them. Indeed, doing so has allowed us to better understand the limitations of human perception in everyday life and to gain new insights into how our visual systems create the picture of the world that we experience each moment our eyes are open.