The Righteous Mind: Why Good People are Divided by Politics and Religion

by Jonathan Haidt

This simple public health intervention worked miracles: lead levels in children’s blood dropped in lockstep with declining levels of lead in gasoline, and the decline has been credited with some of the rise in IQ that has been measured in recent decades.56 Even more amazingly, several studies have demonstrated that the phaseout, which began in the late 1970s, may have been responsible for up to half of the extraordinary and otherwise unexplained drop in crime that occurred in the 1990s.57 Tens of millions of children, particularly poor children in big cities, had grown up with high levels of lead, which interfered with their neural development from the 1950s until the late 1970s. The boys in this group went on to cause the giant surge of criminality that terrified America—and drove it to the right—from the 1960s until the early 1990s. These young men were eventually replaced by a new generation of young men with unleaded brains (and therefore better impulse control), which seems to be part of the reason the crime rate plummeted.