Maybe not. [And if you haven't watched the video of the folks playing basketball while you count how many passes they make, click on the link.]
In an experiment, volunteers are asked to run after a jogger (who is part of the experiment) and count how many times the jogger touches his hat. But what happens when the researchers add in something on the side? Will the volunteer see it?
Two-thirds of the time, no. Not even when what's going in the side is especially violent and startling.
This finding comes too late for Kevin Conley, a Boston cop convicted of perjury when he said he had never seen other cops, all of them involved in an intense chase, who brutally assaulted what turned out not to be the bad guy, but a black cop in plain clothes. Conley was the only cop who even admitted being near the beating. But he claimed not to have seen it.
Read more here.