An article in last Tuesday's Science Times wrote about a seminal psychology film clip called the "Opaque Gorilla Video." It's a short research film meant to test "inattentional blindness," (also known as "IB") the common human ability to look directly at something and not see it. Magicians and politicians have long capitalized on this tendency, but in the hallowed halls of science, the field of IB is relatively new, and cognitive psychologists are still debating whether it is caused by rapid amnesia (inattentional amnesia) or never actually perceiving something in the first place (inattentional blindness).
One of the tools used to test various IB theories is the Opaque Gorilla Video, which is online as an embedded java clip and can be seen here. (I could only view it in Internet Explorer on my PC - it didn't work in Firefox.) In the video, you see two groups of three people passing a basketball back and forth. In the midst of their play, a woman wearing a gorilla suit casually walks into view, beats her chest and then walks off. In one recent study on the effects of alcohol on Inattentional Blindness, test subjects were told to count the number of basketball passes on the part of one team or the other. After watching the video, the subjects were asked of they saw the gorilla. 46 percent of the sober people saw the gorilla, meaning that more than half did not see it. Only 18 percent of the alcohol drinkers saw the opaque gorilla. (This particular study was called "Blind Drunk: The Effects of Alcohol on Inattentional Blindness")
The reason that this film is referred to as the Opaque Gorilla Video is that other IB test films feature unexpected events ("UE's") which are transparent, such as the transparent umbrella woman, it's fantastic remake, and then of course the obligatory opaque umbrella woman. All of these videos and other IB test examples can be viewed from the University of Illinois's Visual Cognition Lab demo page here. So go ahead and do your own experiment - reduce your browser size to hide the context of one of these videos, ask your friends or co-workers to count the number of basket ball passes on the part of the white team or the black team and then a few minutes later, ask a number of questions about the video, including whether they saw the gorilla or umbrella lady.