Do children who kill animals turn out to be violent?

Question

It is widely claimed that children who injure or kill animals as children are more likely to exhibit violent behavior as adults, committing domestic violence or murder. A site dedicated to discussing "killer kids" describes "cruelty to animals & smaller children" as one of the "warning signs of kids who kill".

The People for the Ethical Treatment of Animals (PETA), who actually cite some sources, states that this goes both ways:

Acts of cruelty to animals are not mere indications of a minor personality flaw in the abuser; they are symptomatic of a deep mental disturbance. Research in psychology and criminology shows that people who commit acts of cruelty to animals don’t stop there—many of them move on to their fellow humans. “Murderers ... very often start out by killing and torturing animals as kids,” says Robert K. Ressler, who developed profiles of serial killers for the Federal Bureau of Investigation (FBI).

Studies have shown that violent and aggressive criminals are more likely to have abused animals as children than criminals who are considered non-aggressive. A survey of psychiatric patients who had repeatedly tortured dogs and cats found that all of them had high levels of aggression toward people as well. According to a New South Wales newspaper, a police study in Australia revealed that “100 percent of sexual homicide offenders examined had a history of animal cruelty.” To researchers, a fascination with cruelty to animals is a red flag in the backgrounds of serial killers and rapists. According to the FBI’s Ressler, “These are the kids who never learned it’s wrong to poke out a puppy’s eyes.”

Apparently, even as adults such individuals are still violent toward animals.

Is there any evidence of a correlation between childhood violence toward animals and violent behavior as an adult (or vice versa)?

Answer 1

"Is there any evidence of a correlation?"

Yes. There are known common causes, and those are classified as empathy disorders. fMRI results show that lack of empathy is a real, fundamental brain effect, and humans normally have empathy towards fellow humans as well as animals.

Now, that last result showed that empathy towards other people is not a good predictor for empathy towards animals. I can't obviously cite references for your particular case, but I expect you killed fish for food. That's another part of the brain, gathering food.

Answer 2

I quote the Wikipedia article on psychopathy

Three behaviors — bedwetting, cruelty to animals and firestarting, known as the Macdonald triad — were first described by J.M. MacDonald as possible indicators, if occurring together over time during childhood, of future episodic aggressive behavior. However, subsequent research has found that bedwetting is not a significant factor and the triad as a particular profile has been called an urban legend. Questions remain about a connection between animal cruelty and later violence, though it has been included in the DSM as a possible factor in conduct disorder and later antisocial behavior.

and the one on Cruelty to animals, which makes the interesting point that there may be a common cause to both (I think this runs somewhat counter to this "evil shows itself early" thing that I feel is associated with it)

It has also been found that children who are cruel to animals have often witnessed or been victims of abuse themselves. In two separate studies cited by the Humane Society of the United States roughly one-third of families suffering from domestic abuse indicated that at least one child had hurt or killed a pet.

Unfortunately I don't have access to this article though it promises to be a current review on the matter. This one I do have access to, they urgently call for more research, which may have happened in the meantime.

Answer 3

Basically, yes, there's a correlation. Keeping in mind Oddthinking's comment on the value of such non-random samples, this is where most of the correlational data comes from, e.g.:

A history of childhood cruelty to animals and contemporary patterns of chronic interpersonal aggression has been documented in assaultive incarcerated offenders, perpetrators of sexual homicides, rapists, and child molesters (Felthous, 1980; Felthous & Yudowitz, 1997; Kellert & Felthous, 1985; Merz-Perez, Heide, & Silverman, 2001; Ressler, Burgess, & Douglas, 1988; Tingle, Barnard, Robbins, Newman, & Hutchinson, 1986), making a case for the potential prognostic value of childhood animal cruelty.

As to what is the ultimate cause however, it's nowhere near as simple as MSalters' answer makes it to be, i.e. [lack of] empathy is not the only cause, although it does play a role:

animal abuse was negatively associated with affective empathy and national culture

Childhood animal cruelty (CAC) is also correlated with [prior] exposure to interpersonal and animal violence (same source):

Rural adolescents were more likely to abuse animals and had higher exposure to domestic violence, which (in turn) was associated with more animal abuse.

And as to whether CAC has better predictive value than these other associates... one review says no. Quoting from the first paper:

In a recent review of research on children who are cruel to animals, McPhedran (2009) concluded that the home environment is generally a better predictor of the development of adult violence than childhood cruelty to animals and we should not infer that animal cruelty leads to other antisocial behaviors throughout development. McPhredran suggested that the context within which cruelty to animals occurs is most likely the common factor, and that the complex nature of abusive home environments and experiences that contribute to behavioral problems and interpersonal violence should be an important target of our interventions.

citing

McPhedran, S. (2009). Animal abuse, family violence, and child wellbeing: A review. Journal of Family Violence, 24, 41–52.

Alas all review works in this area seem to be of the narrative kind, so the quality of inference (one way or the other) is likely to be biased.

McPhedran's review seems to be talking at some length about what appears to be the New South Wales study that prompted your question, and Oddthinking's comments (on the lack of controls etc.) are reflected in McPhedran's review as:

Although Gullone and Clarke (2006) contend that there appears to be a greater likelihood that people alleged to have abused animals will engage in offenses against the person when compared to all alleged offenders, they did not specify the order of offending. Thus it cannot be concluded that animal cruelty preceded other offenses. It must also be noted that although 25% of animal abuse offenders committed offenses against the person, this entails that 75% of animal abusers did not commit offenses of that nature. It is acknowledged that offenses may have been committed but not detected by police, but it should also be considered that this appears an insufficient explanation to account for the entire 75% of animal abusers who did not commit offenses against the person. Therefore, the findings simply support existing evidence that animal cruelty, and particularly the deliberate infliction of unnecessary physical pain or suffering, may occur in conjunction with a wider range of antisocial behaviors. Similar patterns of generalized criminality among animal cruelty offenders have been noted in New South Wales, Australia (Gullone and Clarke 2006). The range of criminal behaviors performed by persons in New South Wales Police databases with a record of animal abuse averaged four different types of criminal offence. Assault, followed by stealing, driving offences, and domestic violence were the most common forms of crime committed by animal cruelty offenders in New South Wales who had other criminal charges. However, the New South Wales animal cruelty offender statistics were not compared against a wider sample of offenders without a history of animal cruelty. Therefore, it cannot be concluded that patterns of generalized criminal offending among animal cruelty offenders differed from patterns of generalized criminal offending either overall or among offenders who did not commit animal cruelty.

McPhedran also critiques the lack of operational definition for animal cruelty in some of the research in this area.

And this is in fairly strong contrast with a paper by Simmons et al. (2014), which although is not centered on [interpersonal] violence, does make pretty bold claims as to the predictive value of animal cruelty and appears to have decently large and representative samples:

The objective of this study was to document the long-term relationship between youthful animal abuse and a variety of problem behavior outcomes later in life. Data were used from a national, longitudinal, and multigenerational sample collected by the National Youth Survey Family Study, which assessed families across 27 years from 1977 to 2004. The analytic sample consisted of 2538 individuals who were analyzed using multivariate ordinary least squares and logistic regression modeling that controlled for important demographic factors. Hypotheses were tested across two generations separately showing that a history of animal abuse does, indeed, predict later problem behaviors, including serious offending, marijuana use, other drug use, alcohol use, and deviant beliefs. Depending on the outcome examined, each model accounts for 5–34% of the variation in respondents’ problem behaviors. Within each model, animal abuse was often one of the strongest predictors.

So what to conclude from all this? Low quality primary studies leave substantial leeway for investigators or reviewers to interpret the data according to their own predispositions or agendas. Also, since all these studies are observational, you can never rule out all confounders etc. What's the best predictor may depend on what you included or not in the model etc. So big grain of salt prescribed for the reader and perhaps more research needed.