We evolved as a species to respond properly to a world that was more or less consistent. Whether trees, rocks, food or other people, the objects in our environment tended to be consistent in their appearance from one moment to the next.
Therefore it is not surprising that humans (and many other species as well) exhibit change blindness. When some object within our view changes in appearance, while we are not focusing on that particular object, we tend not to notice.
This has enormous potential consequences for the coming age of wearable computers. Since these wearables will be tracking our gaze direction, software designers will be able to know where we are focusing our gaze direction, and when we are in the middle of a saccade between one object of interest and another.
This will make it easier for malicious software to modify the appearance of objects in our augmented view, without our ever realizing that anything has changed. In other words, we may no longer be able to rely on the evidence of our own senses.
We might need to start relying on algorithms that analyze the visual scene before us, looking for unexpected alterations. Such algorithms could, for example, be able to determine whether somebody is really handing you a dollar coin, or whether they are actually giving you a nickel that was just made to look, for a moment, like a dollar coin.
Which, when you think about it, gives a whole new meaning to the phrase “change blindness”.