A Gorilla Walks Into a Room . . .


Photo by Michael Nichols


Since 1989 more than 250 convicted criminals have been exonerated based on DNA evidence.  About 75% of those exonerations came in cases where eyewitnesses had misidentified the subject or the events.  This Supreme Court is currently hearing arguments questioning the validity of using witness testimony, but scientists have been questioning the accuracy of our memories for years. The American Psychological Association says, “Controlled experiments as well as studies of actual identifications have consistently found that the rate of incorrect identifications is approximately 33 percent.”

Why are witness accounts so unreliable?  Our brains often fail to retain relevant information and the memories we do have are susceptible to suggestion, influenced by our emotions and liable to be embellished with imaginary details.

We are likely to miss the most obvious of events. In a 1999 Harvard study, participants were asked to watch a video of people passing a basketball and to count how many times those players dressed in white passed the ball.   Concentrating on the task, half of the study participants failed to notice a person in a gorilla costume strolling through the middle of the players.

Unfortunately, regardless of its reliability, juries tend to place trust in eyewitness testimony, especially if the testimony is confidently expressed. Researchers are trying to use their findings to make trials fairer and testimony more reliable by changing line-up procedures and making sure uncertainties are clearer to witnesses and jurors, for example.

For all the latest science news, check out the National Geographic’s twice-weekly news rundown, Earth Current.

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