Individuals engage in paraphilias which are organized along a continuum; participating in varying levels of fantasy perhaps by focusing on body parts (partialism), symbolic objects which serve as physical extensions of the body (fetishism), or the anatomical physicality of the human body; specifically regarding its inner parts and sexual organs (one example being necrophilia).[37] A disproportionate number exhibit one, two, or all three of the Macdonald triad of predictors of future violent behavior: Many are fascinated with fire setting.[7] They are involved in sadistic activity; especially in children who have not reached sexual maturity, this activity may take the form of torturing animals.[7] More than 60 percent, or simply a large proportion, wet their beds beyond the age of 12.[7][38] They were frequently bullied or socially isolated as children or adolescents.[7] For example, Henry Lee Lucas was ridiculed as a child and later cited the mass rejection by his peers as a cause for his hatred of everyone. Kenneth Bianchi was teased as a child because he urinated in his pants, suffered twitching, and as a teenager was ignored by his peers.[7] Some were involved in petty crimes, such as fraud, theft, vandalism, or similar offenses.[39] Often, they have trouble staying employed and tend to work in menial jobs. The FBI, however, states, "Serial murderers often seem normal; have families and/or a steady job."[16] Other sources state they often come from unstable families.[7] Studies have suggested that serial killers generally have an average or low-average IQ, although they are often described, and perceived, as possessing IQs in the above-average range.[7][16][40] A sample of 202 IQs of serial killers had a median IQ of 89.[41]