Saw this: http://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline

Lead emissions from tailpipes rose steadily from the early '40s through the early '70s, nearly quadrupling over that period. Then, as unleaded gasoline began to replace leaded gasoline, emissions plummeted.

Intriguingly, violent crime rates followed the same upside-down U pattern... The two curves looked eerily identical, but were offset by about 20 years.

They claim a strong methodology: they studied during the phaseout of leaded fuel (which was not implemented uniformly across places, crucially) and subsequent violence levels. The same trend was proved across the world. Lead shrinks the part of the brain responsible for empathy, hence where lead poisoning was more common, people are more predisposed to violence. Big cities thus become more violent.

Do widely-spread brain toxins explain more violence? Are many violent criminals people who got their prefrontal cortexes shrunk by toxins? Do big cities make people aggressive and violent due to increased concentration of toxins?

  • $\begingroup$ Welcome to CogSci.SE! A few suggestions: at the end of the question you actually have 3 questions. I would recommend creating separate questions on CogSci for each. Remember that we ask you to do some initial research first though! Speaking of research, have you read the entire Mother Jones article? Considering the amount of evidence that they have, I would highly doubt that there is any other explanation... $\endgroup$
    – BenCole
    Jan 4, 2013 at 21:17
  • $\begingroup$ @BenCole I meant them to be slightly redundant ways. I asked of a trend; big cities are extremes of this trend, and its pertinent to me; hence third question. :-) Second question was to avoid "technically correct" generalizations that can confuse me. Yes I have read it all. And I do want to learn of similar research which is now highly regarded. $\endgroup$ Jan 4, 2013 at 21:41
  • $\begingroup$ I understand now. I'm curious still: do you doubt the research or linked papers in the article? It seems that the article, or the linked papers, readily answer your first question. Unfortunately, I suspect there are many reasons for a slightly smaller prefrontal cortex than just toxins and more reasons for violence than a small prefrontal cortex. Also, considering that anything in sufficient quantity can be a toxin, I suspect that the last two questions are too broad for us to be able to answer here. $\endgroup$
    – BenCole
    Jan 4, 2013 at 22:16
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    $\begingroup$ I think the important distinction here is "factor in" versus "explain". Could it be a factor? Certainly. However, to say that things like population density aren't a larger contributor would be ignoring a lot of already established notions. I think it's a great question and worth asking, it's just likely to be more complicated, as Ben pointed out. $\endgroup$ Jan 5, 2013 at 18:19
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    $\begingroup$ I've heard the exact same phenomenon( difference I violence rates) being explained by a completely different thing. What it was escapes me now, but I don't think there is a single simplistic explanation, like lead. $\endgroup$
    – Alex Stone
    Jan 6, 2013 at 14:41

1 Answer 1


There is some truth to this. I don't have the time to go into details but I've found an interesting link..



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