I love finding—or inventing—ways to categorize people.

I agree with philosopher Isaiah Berlin, who observed, “Every classification throws light on something.”

I’ve devised several of these, and of the ones I’ve come up with, my favorites are the Abstainer/Moderator distinction and the Four Rubin Tendencies.

Because of this interest, I was intrigued to come across the Psychopathic Personality Inventory—a personality test for traits associated with psychopathy.

I think we can all agree that one thing that does not contribute to a happy life is a relationship with a psychopath. But what traits are associated with psychopaths?

The test seeks to measure:

Social influence: a tendency to seem charming, persuasive

Fearlessness: a tendency to embrace risk without fear or anxiety

Stress immunity: stays cool in difficult circumstances

Machiavellian egocentricity: a tendency to consider only personal needs

Rebellious nonconformity: a tendency to neglect social conventions and regulations

Blame externalization: a tendency to assign blame for problems or obstacles to other people

Carefree lack of planning: limited willingness to make future plans

Cold-heartedness: no guilt or remorse

People throw around the terms “sociopath” and “psychopath” quite frequently, but these are technical terms with very specific meanings. That said, if there’s someone in your life who seems to show many of the above traits, it might be useful to reflect on that.

Do you know anyone who fits these traits? To my great relief, I realize I don’t.

Also…

• In my research for Before and After, I’ve identified eighteen strategies for changing habits, and one of the most well known and popular is the Strategy of Monitoring. If, like me, you get a kick out of monitoring yourself, check out Quantified Self—“self knowledge through numbers.”

Gretchen Rubin is the author of the #1 New York Times Bestseller The Happiness Project—an account of the year she spent test-driving the wisdom of the ages, current scientific studies, and lessons from popular culture about how to be happier—and the recently released Happier at Home. On her popular blog, The Happiness Project, she reports on her daily adventures in the pursuit of happiness. For more doses of happiness and other happenings, follow Gretchen on Facebook and Twitter.

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*Image courtesy of Boston Public Library