Rick Nevin
Causation Indicator: Coherence

    Bradford Hill states that a causal interpretation “should not seriously conflict with the generally known facts of the natural history and biology of the disease” The association between blood lead, MR, SAT scores, and crime and unwed teenage pregrnacy trends reveals an ecological coherence with controlled studies linking individual lead exposure to neurobehavioral damage.  The racial convergence in MR prevalence and SAT scores across slum clearance birth years is also consistent with the known history of heavily leaded paint use in older housing, and lead dust and paint chip ingestion risks in severely deteriorated city slums.  Lead exposure trends also reveal a coherent relationship with international trends in IQ and social behavior that is correlated with IQ.  The cognitive and behavioral effects of preschool lead exposure can also reconcile the seeming incoherence of controversial research on IQ correlates in The Bell Curve, and temporal trends in those behavioral correlates.

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