It happened in 1995. Boston cop Kenny Conley was pursuing
a suspect and ran right past other cops beating a man. Conley
later testified that he never saw the beating. He was convicted of
perjury and obstruction of justice, and sentenced to 34 months in
prison.

But did he tell the truth that he saw nothing? Very possibly, says
a study in the journal i-Perception.

Researchers had individuals "chase" a "runner" for on a college
campus at night. The subjects followed the runner at a distance
of 30 feet and had to count the number of times he touched his
head. Each chase passed a staged fight designed to look like
the scene Conley rushed by: two actors staged a beatdown on a
third man, with kicking, punching and yelling.

And two-thirds of the subjects did not recall seeing the fake fight.
Even when repeated during the day, only 60 percent saw the
beating.

Such a gap in perception is called inattentional blindness. It
occurs when increased demands on one's attention decrease
the ability to notice something unexpected. And a dangerous
consequence is that we don’t believe we miss as much as we
actually do.

—Christie Nicholson