Tragic example of perception gone wrong

When I read the book Invisible Gorilla by Christopher Chabris and Daniel Simons I was struck by the story of Kenny Conley, the Boston police officer who failed to notice a brutal assault while he was chasing a suspect. Conley later testified that he simply did not see the assault because he was focused on the suspect he was chasing, but a jury did not believed him, convicting him of perjury (which was later revered on appeal). Chabris and Simons did a very clever experiment modeled on Conley's experience and - well, let's just say that their experiment supported the real life experience. (Their research is available here and is an ideal short research paper to use with your students.)

Photo via the Los Angeles Times

What made me think about this was reading another story this morning about police who made another kind of perceptual mistake: misidentifying innocent people as a wanted criminal, and opening fire on them. Police in Los Angeles were hunting for an ex-cop who had allegedly killed one officer and perhaps others, and a number of officers were stationed near the home of a high-ranking police official whom they believed may be the next target of the ex-cop.

This Los Angeles Times article then describes how it went very wrong:

The officers' radio crackled with an urgent warning: He could be coming your way.
It was around 5 a.m. in Torrance on Thursday and police from nearby El Segundo had seen a pickup truck exit a freeway and head in the general direction of the Redbeam Avenue residence of a high-ranking Los Angeles police official, which was being guarded by a group of LAPD officers.
Police were on the lookout for Christopher Jordan Dorner, a disgruntled ex-cop suspected of hunting down members of the LAPD and their families in a twisted campaign of revenge. The radio call indicated that the truck matched the description of Dorner's gray Nissan Titan.
A few minutes later, a truck slowly rolled down the quiet residential street.
As the vehicle approached the house, officers opened fire, unloading a barrage of bullets into the back of the truck. When the shooting stopped, they quickly realized their mistake. The truck was not a Nissan Titan, but a Toyota Tacoma. The color wasn't gray, but aqua blue. And it wasn't Dorner inside the truck, but a woman and her mother delivering copies of the Los Angeles Times.

It sounds like a case of perceptual set, where the officers were told what they were about to see and despite the differences in the actual vehicle and the one they were expecting. I also supposed that because they were under enormous pressure (and still are) to find this former cop they were quick to act first rather than carefully verifying what they were seeing.

I realize that the reaction of the public will probably be like that of the neighbor quoted in the article who asks how the police could have mistake two Hispanic women for one African-American male. But I suspect that students of perception could see how this tragedy could have happened. Sometimes when you're looking for a gorilla, anything that's ape-like might seem to fit the bill.

--posted by Steve

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