Inattentional blindness


 * This article discusses the psychological concept of Inattentional Blindness'.

Inattentional blindness, closely related to the subject of change blindness, is observed phenomena of the inability to perceive features in a visual scene if they are not being attended to. That is to say that humans have a limited capacity for attention which thus limits the amount of information processed at any particular time. Any otherwise salient feature within the visual field will not be observed if not processed by attention.

Experiments demonstrating inattentional blindness
The most well known study demonstrating inattentional blindness was conducted by Daniel Simons of the University of Illinois at Urbana-Champaign and Christopher Chabris of Harvard University. In their study, subjects are asked to watch a short video in which two groups of people (wearing black and white t-shirts) pass a basketball back among themselves. The subjects are told to either count the number of passes made by one of the teams, or to keep count of bounce passes vs. aerial passes. In different versions of the video a woman walks through the scene carrying an umbrella, or wearing a full gorilla suit. In one version the woman in the gorilla suit even stops in the middle, faces the camera, and pounds her chest before walking out of the scene. 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 we are mistaken with regard to how important events will automatically draw our attention away from current tasks or goals. This result indicates that the relationship between what is in our visual field and perception is based much more significantly on attention than was previously thought.

Another reserach finding was done by Steve Most, Chabis and Scholl. They had objects moving up and down 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 nonetheless missed it. They had found that people may be attentionally tuned to certain perceptual dimensions, such as brightness or shape.

Thus the common saying "out of sight, out of mind", meaning that people usually don't think about what they do not see, could be reversed into: "out of mind, out of sight".

Current research
The latest finding was produced by Most, Scholl, Clifford and Simons (2005). There seems to be strong support for the attentional resources to be mediated by the attentional set. Chun & Marois are also a good review.