|“||The FBI has found that a history of cruelty to animals is one of the traits that regularly appear in its computer records of serial rapists and murderers, and the standard diagnostic and treatment manual for psychiatric and emotional disorders lists cruelty to animals as a diagnostic criterion for conduct disorders.||”|
Helen Gavin wrote however in Criminological and Forensic Psychology (2013):
|“||This is not a universal trait, though. Dennis Nilsen had difficulty initiating social contact with people, but loved his faithful companion, Bleep, a mongrel bitch. After his arrest, he was very concerned for her welfare, as she was taken to the police station too.||”|
Alan R. Felthous reported in his paper "Aggression Against Cats, Dogs, and People" (1980):
|“||A survey of psychiatric patients who had repeatedly tortured dogs and cats found all of them had high levels of aggression toward people as well, including one patient who had murdered a boy.||”|
This is a commonly reported finding, and for this reason, cruelty to animals is often considered a warning sign of potential violence towards humans.
In the United States, since 2010, it has been a federal offense to create or distribute "obscene" depictions of "living non-human mammals, birds, reptiles, or amphibians ... subjected to serious bodily injury". This statute replaced an overly broad 1999 statute which was found unconstitutional in United States v. Stevens.
Critics of the concept of a propensity for cruelty to humans cite the fact that animals can be cruel to some animals yet caring to other animals, combined with Pavlov's studies using metronomes at different rates to test conditioned learning showing that humans can discriminate in fine ways that animals cannot, and conclude that there is no such general basis. The exact way these critics explain studies that seems to show links varies, but most of them state that psychiatric and criminological studies are subject to institutional bias and self-fulfilling prophecies. It is also pointed out that correlation does not prove causation.
On the other hand, Piers Beirne, a professor of criminology at the University of Southern Maine, has criticized existing studies for ignoring socially accepted practices of violence against animals, such as animal slaughter and vivisection, that might be linked to violence against humans.
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- Helen Gavin (2013). Criminological and Forensic Psychology. p. 120.
- Felthous, Alan R. (1980). "Aggression Against Cats, Dogs, and People". Child Psychiatry and Human Development. 10: 169–177. doi:10.1007/bf01433629.
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