Police officers and students exhibit an apparent “hierarchy of bias” in making a split-second decision whether to shoot suspects who appear to be wielding a gun or, alternatively, a benign object like a cell phone, research conducted by the Ƶ-Boulder and San Diego State University has found. Both the police and student subjects were most likely to shoot at blacks, then Hispanics, then whites and finally, in a case of what might be called a positive bias, Asians, researchers found.