As part of his effort to demonstrate that as firearms proliferate in the U.S.A. crime declines, Rush Limbaugh on Thursday claimed "You go back all the way to the forties and fifties, and you will see that mass shootings, like at Sandy Hook Elementary in Newtown or whatever, are down. They don't happen nearly as much as they used to."
You won't be surprised to learn that Limbaugh is wrong, as Ezra Klein finds six of the eleven deadliest shootings in the nation have occurred since 2007. But Limbaugh is right about one thing (cue the trite stopped clock joke): gun violence is down in the U.S.A.
Gun violence is down, as is violent crime generally, and as is crime generally.
The reasons probably are numerous and uncertain. Philadelphia Inquirer reporter Stacy Burling profiles psychologist and University of Pennsylvania professor Adrian Raine, author of the recently published The Anatomy of Violence, The Biological Roots of Crime, who recognizes "there's never going to be perfect prediction" of who will turn to violent crime. Nevertheless, he notes
...criminal behavior, like many illnesses, results from a combination of genetic, physical, and environmental risk factors.
"They are on the right path, in part," he said of those who study the nurture part of the equation. "All I'm saying is that there's another path. There's biology, and that has to be recognized."
He's also studied the brains of psychopaths and found they have less gray matter in the prefrontal cortex and smaller amygdalas, a part of the brain that processes emotion. Asked to ponder a difficult moral question, Raine said they knew right from wrong, but showed less activation in the amygdala than normal people. "Emotion is the engine that drives moral behavior," he said.
Less gray matter in the prefrontal cortex and smaller amydalas may be a key factor in crime causation. In a 2007 study published in PLos Medicine, the researchers observed
Childhood lead exposure is associated with region-specific reductions in adult gray matter volume. Affected regions include the portions of the prefrontal cortex and ACC responsible for executive functions, mood regulation, and decision-making. These neuroanatomical findings were more pronounced for males...
And not coincidentally, males are more violent than females. Kevin Drum found that Rick Nevin, responsible for the groundbreaking work on the connection between lead and criminality discovered in the mid '90s
if you add a lag time of 23 years, lead emissions from automobiles explain 90 percent of the variation in violent crime in America. Toddlers who ingested high levels of lead in the '40s and '50s really were more likely to become violent criminals in the '60s, '70s, and '80s (and later) collected lead data and crime data for Australia and found a close match. Ditto for Canada. And Great Britain and Finland and France and Italy and New Zealand and West Germany. Every time, the two curves fit each other astonishingly well. When I spoke to Nevin about this, I asked him if he had ever found a country that didn't fit the theory. "No," he replied. "Not one."
Summarizing the results of a study published by Julia Woolpaw Reyes the same year (2007) as Nevin's latter research, Drum explains
During the '70s and '80s, the introduction of the catalytic converter, combined with increasingly stringent Environmental Protection Agency rules, steadily reduced the amount of leaded gasoline used in America, but Reyes discovered that this reduction wasn't uniform. In fact, use of leaded gasoline varied widely among states, and this gave Reyes the opening she needed. If childhood lead exposure really did produce criminal behavior in adults, you'd expect that in states where consumption of leaded gasoline declined slowly, crime would decline slowly too. Conversely, in states where it declined quickly, crime would decline quickly. And that's exactly what she found.
The impact of lead in the environment upon violent crime remains unproven, though evidence is mounting. There isn't much certain in the world of crime- except that, contrary to what Rush Limbaugh may think, violent crime isn't dropping because too few 5-year-olds and 4-year-olds are wielding guns.