When something changes in our visual field, it seems obvious that the bigger the change the more likely it is that we would notice. However, much research has shown that in fact, we are often blind to large changes when we don’t know to focus on them. An interesting video posted on Boing Boing demonstrates the change-blindness effect well. In this experiment, participants walk over to a desk and are given a consent form to sign by an experimenter. When the experimenter bends down to “put the form away”, a completely different experimenter (wearing a different colored shirt) stands up and continues the instructions. Over 75% of participants fail to notice that the man who stands up is not the same man with whom they had just been conversing.
According to Simons and Ambinder (2005), most research on change blindness has shown that when a major change occurs outside of a person’s visual field (as opposed to a change that is visible as it happens) or in a situation where they are distracted, people are particularly bad at noticing any change. The failure to notice change seems to occur not because of an inability to represent visual information but because we aren’t very good at comparing information from before with information presented after the change. Change blindness is important to understand because people assume that they notice major changes when they actually do not. For example, in witness identification, people might not be accurate spotting differences between people coming and going. Another example, cited by the authors, is in driving safety; people assume they would notice a pedestrian crossing the street even if distracted by talking on a cell phone. The change-blindness effect shows us that we are not as capable of noticing changes in our visual environment as we think we are.