Her research work focuses on what turns some people into violent criminals.

What is research showing on the interplay of social and biological factors in putting a young child at risk in becoming violent and antisocial?

No particular ethnic, racial or a religious group has shown itself to be innately or enduringly more violent than any other (though some from time to time seemed to distinguish themselves). Nor, with rare exceptions, have any generic characteristics been shown to be linked specifically to violent behaviors. Recently there have been studies demonstrating an association between specific gene anomalies and the abnormal metabolism of certain neurotransmitters affecting temperament. However, these anomalies have been associated with problems in adaptation and not specifically with violence.

The social and biological sciences have come to recognize that the most important influences on violence are environmental or experiential. There is abundant evidence that a history of maltreatment is often a precursor of aggressive behavior. Overheating, crowding, isolation and uncomfortable living conditions promote aggression in animals and humans.

Probably the most powerful generator of aggression in living beings is pain. Animals that have been tortured and children who have been severely and repeatedly abused often become extremely aggressive. Animals and humans raised in the company of violent adults is associated with the development of aggressive behavior patterns.

The effects of repeated exposure to violent adults are not simply psychological (e.g., the result of learning or of displaced rage). There are physiological and even neuroanatomical consequences of aggressive upbringing. In response to stressors, changes in gonadal hormones, cortisol and a variety of neurotransmitters affect brain development, brain function and behavior. For example, many of the environmental stressors cited above can lower serotonin levels in the brain. Low levels of serotonin are associated with irritability, impulsivity, depression, and violence. Changes in levels of central nervous system neurotransmitters and damage to certain parts of the brain are also associated with over suspiciousness or paranoia, one of the most common symptoms of repeatedly violent offenders. Paranoia increases fearfulness and a tendency to retaliate for real or imagined threats.

The above data regarding abuse, brain damage and paranoia notwithstanding, most abused children do not become violent; most brain injured people are not violent; and most mentally ill people are not violent. Our own studies on children, adolescents and adults indicate that the constellation of intrinsic psychiatric and/or neurological vulnerabilities and an upbringing in a violent abusive household is a far better predictor of later violence than abuse or brain damage or psychotic thinking alone.

In short, whatever increases impulsiveness and irritability, engenders by hypervigilence or paranoia, diminishes judgment and the ability to recognize one's own pain and that of others, enhances violence. Abusive neglectful parenting does all of these things.

Similarly, our correctional system reproduces all of the ingredients known to promote violence: isolation, discomfort, pain, exposure to other violent individuals and general insecurity. In our prisons we have created a laboratory that predictable reproduces and reinforces aggression. Perhaps with a hit of ingenuity we could do the opposite.

Also: Read Lewis' paper "From Abuse to Violence: Psychophysicological Consequences of Maltreatment."