NPR Radio covers an amazing inattentional blindness experiment that investigated how easy it is to miss a vicious beating in the street – after a policemen was convicted of ignoring an attack during a pursuit.
Inattentional blindness is the phenomenon where we don’t notice something seemingly obvious because we are paying attention to some other details.
It was most famously demonstrated by the ‘gorillas in our midst’ experiment where observers asked to count the number of passes between basketball players fail to notice a man in a monkey suit walking though the action.
Following a policeman’s conviction for supposedly ‘keeping quiet’ about a beating that he ran past while in pursuit of someone else, the same researchers wanted to know whether people asked to follow a jogger and monitor their behaviour would miss a simulated attack in the street.
Then about a minute in the run, slightly off to the side, [researchers] Chabris and Simons had three students stage a fight.
“We had two students beating up a third, punching him and kicking him and throwing him to the ground,” Chabris says.
The question was whether the students would see the fight, and under the conditions — nighttime — that most closely resembled [policemen] Conley’s experience. The numbers were shockingly low.
“Only about a third of the subjects reported seeing the fight that we had staged,” says Chabris.
It’s a brilliant piece of applied research, a great report with an amazing backstory, and the full text of the study is available online if you want more details.
Mind Hacks 
Interesting. It also makes a point for not judging other people (in this case the policeman accused of “ignoring”).
Douglas Adam’s described this phenomenon in his “Hitchhiker’s Guide to the Galaxy” books. Even based an Invisibility device on it.
The “SEP” field. Somebody Elses Problem. Works very well on large city dwellers. Anything like that is Sombody Elses Problem so keep walking, don’t look, don’t get involved.
All large city dwellers are instilled with this principle from childhood.
Hm. Kind of like the “invisible” violence we Americans pay to conduct in Iraq, Afghanistan, Libya, Pakistan, Somalia, and who knows where else every day. We remain blissfully inattentive because there is no draft and we’ve been asked to pay attention to a range of details from corporate talking heads to our ever-diminishing (unless you’re in the top five percent) income. Meanwhile we jog right along as we fund the killings of dozens of innocents on the least violent weeks.