How Perceptual Blindness Works - Simple test shows how Humans (yes, even you) sometimes completely miss things that are in plain sight - Try the test

by | Dec 16, 2009 10:00 AM ET

On Monday we discussed Change Blindness. Today we discuss Perceptual Blindness - the phenomenon where people do not see things that are right in front of their faces. Here is an awareness test that demonstrates Perceptual Blindness for many people:

Another demonstration:

You may have been surprised by the fact that you could completely miss something that is right in front of you, but it happens all the time. As with Change Blindness, it occurs because human beings can only focus on a small number of things in the visual stream. When we are intently focused on something, we do not have a way to "see" other things in the scene. It is also known as Inattention Blindness.

Perceptual Blindness is an essential part of magic tricks, as demonstrated here:

See also: Magic and the Brain: Teller Reveals the Neuroscience of Illusion

According to this article:

After watching the video the subjects are asked if they saw anything out of the ordinary take place. In most groups, 50% of the subjects did not report seeing the gorilla. Simons interprets this by stating that people are mistaken with regard to how important events will automatically draw their attention away from current tasks or goals. This result indicates that the relationship between what is in one's visual field and perception is based much more significantly on attention than was previously thought.
Another experiment was carried out by Steve Most, Daniel Simons, Christopher Chabris, and Brian Scholl. They had objects moving randomly on a computer screen. Participants were instructed to attend to the black objects and ignore the white, or vice versa. After several trials, a red cross unexpectedly appeared and traveled across the display, remaining on the computer screen for five seconds. The results of the experiment showed that even though the cross was distinctive from the black and white objects both in color and shape, about a third of participants missed it. They had found that people may be attentionally tuned to certain perceptual dimensions, such as brightness or shape.

The problem with Perceptual Blindness is that it can sometime affect us in critical situations, as described here:

NASA conducted an experiment in a flight simulator in which commercial pilots were tested to see if they would notice distractions on a runway during simulated landings. Those who were trained pilots did not notice and landed directly on top of the distraction 1/4 of the time, while untrained pilots didn't know what to expect of a typical landing and thus saw the distraction.

It is also the reason why motorists will sometimes hit pedestrians, motorcyclists and bicyclists and then claim they never saw them. Motorists sometimes focus on "cars" and can therefore be blind to everything that isn't a car.

See also: How Change Blindness Works

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