This is a genuine psychological test.

The test is just one question. It's a story about a girl. This girl was, her mother died, she was at her mother's funeral, where she met a guy.

She didn't know him before. Anyway, she fell totally in love. The guy was amazing, she thought. He was wonderful. She, he was her dream guy and she fell madly in love.
But she was too shy to get his name or number there, and when she asked people later no one knew who she was talking about. A few days after that, she killed her own sister.
Now this is the question: why did she kill her own sister? What was her motive?

Now think. Wait for a while, before looking at the answer.

Answer:

The logical reason would be because he would come to her sister's funeral too, and she'd have another chance to meet him.

Comment:

This is an urban legend - that a "famous American psychologist" had developed a one-question test to see if someone had the mentality of a serial killer. As if a single question could expose a psychopath. And this famous American psychologist administered this test to lots of serial killers in prison and they all got it "right". As if a psychopath's problem-solving ability were any different from anyone elses, and as if this could be exposed with a single, shallow question.

"Psychos don't fall in love, you idiot." - by Mig :)