Ch, ch, ch, ch, changes . . .

Abstract

Remember watching those old, low-budget comedy shows in which an actor approaches a pedestrian and asks for directions to a coffee shop? While the pedestrian attempts to help, two people pass between the actor and the pedestrian carrying a large door. During this brief interruption, the actor is replaced by another actor, unbeknown to the pedestrian. But even though the two actors look quite different and may have different voices and clothing, the pedestrian somehow fails to notice that they are speaking to a different person after the door has passed in front of them. This and related phenomena are examples of 'change blindness' and are more common than you might think. Just think of all the road accidents in which the driver claims that the pedestrian 'just appeared from nowhere'. Change blindness has been studied experimentally for several years and seems to occur when the changes to a scene that normally produce a motion signal coincide with another event that disrupts that motion signal. Under these conditions, observers are often blind to surprisingly large changes in the visual scene.