Diallo, a West African immigrant in New York, matched a description of a rapist. Four white officers questioned him, and when the unarmed Diallo started to pull out his wallet, they decided it was a gun and fired forty-one shots. The underlying neurobiology concerns "event-related potentials" {ERPs}, which are stimulus-induced changes in electrical activity of the brain {as assessed by EEG-electroencephalography}. Threatening faces produce a distinctive change {called the P200 component} in the ERP waveform in under two hundred milliseconds. Among white subjects, viewing someone black evokes a stronger P200 waveform than viewing someone white, regardless of whether the person is armed. Then, a few milliseconds later, a second, inhibitory waveform {the N200 component} appears, originating from the frontal cortex-"Let's think a sec about what we're seeing before we shoot." Viewing a black individual evokes less of an N200 waveform than does seeing someone white. The greater the P200/N200 ratio {i.e., the greater the ratio of I'm-feeling-threatened to Hold-on-a-sec}, the greater the likelihood of shooting an unarmed black individual.
( Robert M. Sapolsky )
[ Behave: The Biology of Humans ]
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