Inattentional blindness is a phenomenon related to perception. Inattentional blindness occurs when a visual information is in plain sight of a viewer, but the viewer does not notice it. For instance, in one famous experiment (Simons & Chablis, 1999), subjects were asked to watch a minutes-long video of a basketball game, and count the number of times that the teams changed possession of the ball. During the video, a person dressed in a gorilla suit walks out onto the court and dances a jig. Even though this is a central and visible event, most subjects fail to notice it, because they are attending to the ball. In short, we are blind to visible events if we are not attending to them.

Inattentional blindness has been used to argue against the traditional representational view of perception, and for the enactive view of perception. According to the enactive view, we do not create detailed representations of the world. Instead, perception is a sensorimotor skill, and is used to access information in the world when it is needed. Inattentional blindness is used as evidence to support the view that representations of the world are not constructed (Noë, 2004, 2009).

References:

1. Noë, A. (2004). Action In Perception. Cambridge, Mass.: MIT Press.
2. Noë, A. (2009). Out of Our Heads. New York: Hill and Wang..
3. Simons, D.J., & Chabris, C.F. (1999). Gorillas in our midst: Sustained inattentional blindness for dynamic events. Perception, 28, 1059-1074.

(Added November 2009)