One psychologist says there’s no such thing as a person who is completely devoid of empathy.

How then can we explain how three Florida teenagers allegedly beat three homeless men, killing one of them?

Psychologists say they can’t speculate about the behavior of these particular teens.

But, in general, scientists know some factors do make it easier for people to act without empathy. Among them: Do the attackers see the victims as part of a lesser, different group? Are the attackers acting in a group rather than as individuals? Were they themselves victims of bullying or abuse? Were drugs involved?

Every time the answer is yes, it gets easier for the attackers to overcome the basic inhibitions against hurting others.

The public will likely learn more about the lives of three defendants during court proceedings in the next several months. Billy Ammons and Brian Hooks, both 18, and Tom Daugherty, 17, have been charged with first-degree murder in the Jan. 12 beating.

Norris Gaynor, who died from his injuries, was bludgeoned so severely that his father could not recognize him. A surveillance video that aired nationwide showed two of the teens repeatedly swinging baseball bats at the head of a man curled up on the ground.

Psychologists generally define empathy as the ability to put yourself in someone else’s shoes.

It’s easy for people to lack empathy for those they perceive as unlike themselves. It’s not surprising to psychologists that the teenagers would prey on the homeless, just as some serial killers have preyed on prostitutes.

Race may have also allowed the teenagers to view the homeless men as different from themselves. The teenagers, who traveled to the scene of their violent spree in an SUV, are white and middle class. Their homeless victims were black, Haitian and Dominican.

Psychologists say teenagers who are leading healthy, happy lives and are connected to school wouldn’t lash out violently. Committing acts of unprovoked violence is strongly correlated with being a victim of violence or bullying.

And drugs and alcohol could have lowered their inhibitions. The teenagers were known to smoke pot, drink alcohol and take Xanax, classmates and neighbors say.

Gaynor’s death has prompted schools and groups to organize programs to teach students empathy for the homeless. Officials in Florida are talking about creating a speakers’ bureau to bring current and formerly homeless people into schools.

© 2006, The Miami Herald.

Distributed by Knight Ridder/Tribune Information Services