But from a purely utilitarian perspective, do such moments of "self-reflection," as the NYPD's Tucker put it, actually lead to fairer policing, especially given the unresolved debate among researchers about how — or even whether — implicit bias governs behavior?

Correll, the psychology professor, says the training itself probably doesn't hurt, but there's an opportunity cost to consider, especially if the effort to "fix" implicit bias in officers displaces other kinds of training or gives a city an excuse to ignore factors that are external to policing.