Larger bias against another race is not reduced bias

From the abstract of Bucolo and Cohn 2010 (gated, ungated):

'Playing the race card' reduced White juror racial bias as White jurors' ratings of guilt for Black defendants were significantly lower when the defence attorney's statements included racially salient statements. White juror ratings of guilt for White defendants and Black defendants were not significantly different when race was not made salient.

The second sentence reports that white mock juror ratings of guilt were not significantly different for black defendants and white defendants when race was not made salient, but the first sentence claims that "playing the race card" reduced white juror racial bias. But if the data can't support the inference that there is bias without the race card ("not significantly different"), then how can the data support the inference that "playing the race card" reduced bias?

For the answer, let's look at the Results section (p. 298). Guilt ratings were reported on a scale from -5 (definitely not guilty) to +5 (definitely guilty):

A post hoc t test (t(75) = .24, p = .81) revealed that ratings of guilt for a Black defendant (M = 1.10, SD = 2.63) were not significantly different than ratings of guilt for a White defendant (M = .95, SD = 2.92) when race was not made salient. When race was made salient, a post hoc t test (t(72) = 3.57, p =.001) revealed that ratings of guilt were significantly lower for a Black defendant (M = -1.32, SD = 2.91) than a White defendant (M = 1.31, SD = 2.96).

More simply, when race was not made salient, white mock jurors rated the black defendant roughly 5% of a standard deviation more guilty than the white defendant, which is a difference that would often fall within the noise created by sampling error (p=0.81). However, when race was made salient by playing the race card, white mock jurors rated the black defendant roughly 90% of a standard deviation less guilty than the white defendant, which is a difference that would often not fall within the noise created by sampling error (p=0.001).

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Here is how Bucolo and Cohn 2010 was described in a 2013 statement from the Peace Psychology division of the American Psychological Association:

Ignoring race often harms people of color, primarily because biases and stereotypes go unexamined. A study by Donald Bucolo and Ellen Cohn at the University of New Hampshire found that the introduction of race by the defense attorney of a hypothetical Black client reduced the effects of racial bias compared to when race was not mentioned (Bucolo & Cohn, 2010). One error in the state's approach in the George Zimmerman murder trial may have been the decision to ignore issues of race and racism.

But a change from 5% of a standard deviation bias against black defendants to 90% of a standard deviation bias against white defendants is not a reduction in the effects of racial bias.

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Note that the point of this post is not to present Bucolo and Cohn 2010 as representative of racial bias in the criminal justice system. There are many reasons to be skeptical of the generalizability of experimental research on undergraduate students acting as mock jurors at a university with few black students. Rather, the point of the post is to identify another example of selective concern in social science.