One of the rallying cries of the criminal justice reform crowd, including us here at Reason, is that American policing policies disproportionately harm blacks and other minorities. These days even mainstream politicians like Rand Paul have been sounding this alarm—he recently told a Rotary Club crowd in Shelbyville, Kentucky, that "the war on drugs has had a disproportionate racial outcome." The ostensible purpose of pointing to these disparities is to showcase how unfair and subjective our law enforcement can be. But according to a new study published in Psychological Science, this may not be what the average white person takes away.

Being made aware of the racial composition of America's prisons actually bolsters white Americans' support for intrusive policing and harsh sentencing policies, according to Stanford University researchers Rebecca Hetey and Jennifer Eberhardt.

In one of their experiments, 62 white Californians watched a video showing mug shots of male prison inmates. Some saw a video in which only a quarter of the men were black; in another video, 45 percent were. Afterward, participants were given the opportunity to sign a real petition to amend California's severe three-strike sentencing statute, which currently mandates 25-years to life in prison upon a third felony offense with no exceptions.

The results: More than half of participants who saw the video with less black men signed the petition. But only 27 percent of those who saw the video with more black inmates signed.

In a second experiment, 164 white New Yorkers were given statistics about prison populations. Some heard about how blacks—who make up 12 percent of the U.S. population total—account for 40 percent of those in American prisons, with white Americans accounting for 32 percent. Others heard the New York City incarceration stats, where blacks make up 60 percent of those incarcerated and whites just under 12 percent.

Participants were then asked if they wanted to sign a petition to end New York City's stop-and-frisk policy. About a third (33 percent) of participants who heard the national statistic were willing to sign the petition, while only 12 percent of those who heard the New York City stat would do so. The second group was more likely to say concern over crime made them hesitant to support ending stop-and-frisk policies.

"Many legal advocates and social activists seem to assume that bombarding the public with images, statistics, and other evidence of racial disparities will motivate people to join the cause and fight inequality," said Hetey. "But we found that, ironically, exposure to extreme racial disparities may make the public less, and not more, responsive to attempts to lessen the severity of policies that help maintain those disparities."

A good reminder to heed the work of British sociologist Stuart Hall and similar communication scholars: Never assume your audience will take away what you intend for them to take away. Between the producing ("encoding" in Hall-speak) and the receiving ("decoding") of a message, there's a lot of space for conscious or unconscious fears and prejudices to meander in.