While in prison, they were shown videos of dozens of different people walking by, and asked which ones they'd choose to attack. And their choices matched up with actual victims.

So, while we may consider ourselves above animals, the savageness of nature exists in all of us, and can play out similarly like in the animal kingdom.

(http://www.autoadmit.com/thread.php?thread_id=3922934&forum_id=2#35641958)