Friday’s shooting at Planned Parenthood is the ultimate political Rorscharch test. Was the shooter motivated by anti-abortion rhetoric or was he just violent and mentally ill? Is he a domestic terrorist enabled by loose gun laws or a disturbed loner without a political agenda? Was this a fluke tragedy, or the inevitable culmination of months of animosity towards Planned Parenthood? One thing is certain: the Planned Parenthood shooting is an example of what psychologists call “confirmation bias,” which is when a person interprets new facts to reinforce or confirm things he or she already believes.