Boys don’t come into the world with some inborn tendency toward domination or violence.

In 1984, developmental psychologist Cynthia Garcia Coll named the inborn tendency to withdraw from unfamiliar situations, people and environments behavioral inhibition.

But in recent years the plethora of names and dates and addresses and organizations in a complicated world appears to have triggered many people’s inborn tendency to note coincidence and improbability, leading them to postulate connections and forces where there are none, where there is only coincidence.

In one courtroom sequence from the 1982 film, a police officer testifies that pachucos have an “inborn” tendency for violence inherited from “the bloodthirsty Aztecs.”

So for the new study, which was published last week in Medicine & Science in Sports & Exercise, researchers at the University of Missouri in Columbia and other schools first gathered rats from a strain that has an inborn tendency to become obese, starting in adolescence.