Monday, May 7, 2012

A gorilla on a basketball court? You'd think you'd notice.

My friend, Brian Joyce, the Ute Gorilla at a Utah football
game. (Photo used without permission).

Our criminal justice system is based largely on eyewitnesses. CSI-type crime shows might make it seem like there is DNA evidence in every case that definitively links one person to every crime, most cases actually revolve around people who saw things.

Unfortunately, there is growing evidence that people can’t see or recall things as well as they think. Take this example: Suppose you were watching a video of two basketball teams passing basketballs back and forth on a basketball court. While they are doing this, a woman in a gorilla suit, walks out onto the court, thumps her chest, and then walks off. You’d notice that, right? And if you didn’t see it, you’d be pretty sure that it didn’t happen while you were watching.

Not necessarily, according to research conducted at Harvard University. Those researchers asked study participants to watch a short video. They were to count the number of passes made by one team and ignore the passes made by the other. While they were focused on this task, the gorilla came out, thumped her chest, and walked away. Half of the participants didn’t see the gorilla. When asked about it, most of them were sure that there was no gorilla in the video. The gorilla was invisible to them because they were temporarily blind to certain things and they didn’t even realize it.

Christopher Chabris and David Simons believe that the subjects were so focused on the relatively difficult tasks of counting the passes made by one team and on ignoring the passes made by the other team that they became blind to information that didn’t relate to those tasks. That finding is interesting, but not totally surprising. We know that when we are focused on one thing we might pay less attention to other things. That is the definition of focus.

The scary thing about the study is that the participants were sure that the gorilla wasn’t on the court during the video. You can imagine these people coming into court and swearing that there was no gorilla. In a criminal case where a defendant might be sent to prison for years, or even put to death, it is frightening to think that we are dealing with such limited perception. They didn’t even know that they were blind.

Barry Scheck’s Innocence Project has shed a lot of light on the errors that can creep into criminal trials. 75% of the wrongful convictions that they have had overturned using DNA evidence depended at least partly on faulty eyewitness testimony. This research by Chabris and Simons gives an explanation of why all those cases got the wrong result. The witnesses might not have been lying. They might have missed the gorilla in the room and not even realized it.

Here is the video that they showed. Can you believe that they missed the gorilla?



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