In the United States today, many experts (though not all) accept some version of what is known as "The Cycle of Violence" theory. First introduced in the 1970s by researcher Lenore Walker, the "Cycle of Violence" theory attempts to isolate patterns of abusive behavior in relationships by a cycle of predictable stages. Abuse of pets, however, is often part of an abusive relationship, or is a precursor to more serious forms of person to person abuse.