"New Zealand's kea* are among the most devastatingly intelligent birds on the planet. For instance, animal cognition researchers say kea are as smart as crows at solving mechanical puzzles. So it comes as a shock to learn that much of what we know about the kea's unusual behavior in the wild comes from studies of birds stultified by lead poisoning. Lead is toxic at such low doses that public health authorities have yet to identify a "safe" level of exposure. Chronic exposure of children to relatively low doses of lead can affect their IQ, and some even argue that lead in gasoline can explain the major crime trends of the twentieth century."