Opinions are divided over the killing of Trayvon Martin; but they are not just divided over the central questions of guilt. People (including the key witnesses) seem to disagree about the facts of what happened that night, commentators disagree about George Zimmerman's motivations, and politicos disagree about what the case says for both race relations and laws governing firearms and self-defense in America. Much of this disagreement is attributable to a handful of biases that emerge as the mind attempts to make sense of ambiguous social information.

First, to the facts. The public does not know the facts and won't know them for some time. Even then, we will only have one complete side of the story—that of Zimmerman. Though eyewitnesses seem to have been present during or soon after the shooting and both Zimmerman and Martin were reportedly on phone calls, these accounts are necessarily imperfect. Though memory encoding—the initial process whereby these witnesses mentally recorded the events they saw and heard—is imperfect in and of itself, the high degree of publicity surrounding this case sets up the conditions whereby misleading or ambiguous information reported in the media and repeated interviews by investigators and journalists may reshape those witnesses' memories. Thus, whatever they have said and whatever they will say to investigators must be taken with a grain of salt. Whatever conclusions Zimmerman and the witnesses drew about the events that night are going to be reshaped and reformulated subconsciously as they run through them in their minds and as they follow news of the events. It is not (entirely) their fault that their stories may change (unless they change them intentionally to distort the truth or protect themselves); remembering accurately is a difficult task for the human mind.

Second, to Zimmerman's behavior and motivations. There is the question of what went through Zimmerman's mind that night as he saw Martin, called the police, pursued, and eventually shot Martin. Indeed, my hometown press MinnPost opened their Monday morning coverage with a provocatively titled story "Who is George Zimmerman, and why did he shoot Trayvon Martin?".

The late psychologist Ziva Kunda wrote in a seminal article, "The case for motivated reasoning," that unless specifically motivated to make accurate judgments and decisions, "People are more likely to arrive at those conclusions that they want to arrive at." Zimmerman—like any human—saw things that he then interpreted within his own mental frameworks based upon his prior experience. We do not know what those frameworks look like or exactly what his prior experiences are, but some evidence suggests that he has often seen suspicious activity in many situations. Zimmerman seems like he may have been looking for criminal behavior in all activity and that means he would be likely to see criminality in a teenager. This in no way justifies his actions, but it may help to explain why he saw things the way he did.

Then, there is the question of a race. Was Zimmerman a racist? Did he act in a racially prejudicial way? Arguments are being made about whether he was a racist and whether his actions were motivated by the race of his victim. Hopefully any truth will eventually come to light about whether he was or was not racist. To the latter question (of racial prejudice), however, there is much that psychology can tell us. Research shows that people are consistently prejudicial toward out-groups (even when those groups are known to be meaningless and arbitrary distinctions). If you are skeptical of rampant prejudice, test yourself with the implicit attitude test, which uses response times to assess one's implicit prejudice for different racial, gender, and age groups. The results might surprise you.

But our subconscious prejudices toward out-groups are no excuse for our actions, particularly when they lead us to violent behavior. An intriguing experiment has recently shown that we can reduce our prejudices by consciously resisting our subconscious inclinations through "thinking safe" (rather than "thinking quick") before judging whether an object associated with a black or white face is a gun. If Zimmerman was predisposed to see criminality in Martin's presence in the neighborhood that night, it is unlikely that he would have been thinking "safe". Motivated reasoning and subconscious prejudice can be a powerful combination and it is possible they played a role here.

This leads to a third and final bias that comes in our own interpretations of the case. Indeed, motivated reasoning of the kind described by Kunda can also help to make sense of our own judgments. We come to this news story with our own understandings—"schemata" as social psychologists call them—that tell us what to make of the information we hear, see, and read. These schemata are developed based upon our own lived experience and the previous news we have read. When we see an ambiguous situation, our mind tries to fit that situation into a schematic category that tell us what is happening in the situation and why. (As a political scientist, I would also note that these schemata might reflect "frames" handed to us by journalists, commentators, and politicians, who aim to shape our understanding of the case for strategic reasons.) If one's first instinct is to see this as a case of self-defense, then they will use our "self-defense" schemata to understand who did what and why, alleviating Zimmerman of guilt for his actions. If instead one's first instinct is to see this as a case of racially motivated killing, then they will use our "racial prejudice" schemata to attribute blame not just to Zimmerman but to a prejudicial motivation in his actions. Everyone will interpret the situation slightly differently depending on how this case fits into their own schemata and what particular evidence they have heard, and that leads to the disagreements in interpretation that are now filling headlines.

These contrasting schemata also reflect a fascinatingly common psychological phenomenon known as the "fundamental attribution error". This error manifests when we attribute other peoples' negative actions to their character and personality while attributing our own negative actions to the context in which we acted. By contrast, the error also manifests when we attribute positive outcomes for ourselves to our own actions and positive outcomes for others' to the context in which they operated. In the racial prejudice frame, we see Zimmerman as shooting Martin because of who he is not because of the context in which he acted. That is, we see Zimmerman as racially prejudiced (as I discussed above). By contrast, in the self-defense frame, we see Zimmerman as acting in self-defense (that is, protecting himself) because of the context. Thus, the frame leads us to different conclusions about his guilt and to different inferences about whether he or the context is responsible. These frames and the psychological schemata that support them prevent us from seeing a combination of contextual and personal explanations for what happened, yielding the polarized views of the case now being aired.

Lacking much evidence of what occurred, our mind makes sense of the ambiguity of the situation through the only means it knows how. Predisposed conclusions—driven by the fundamental attribution error, our own motivated reasoning and schemata regarding the case, and the frames handed to us through media—lead us to believe what we want to believe rather than deliberate over the evidence or, perhaps better, wait for justice to be served via a thorough investigation and a deliberation of the facts that investigation reveals through trial.

Kunda's argument that motivations lead us to conclusions we want to reach had a flip side. Though we are often motivated to think, judge, and decide in a particular way in defense of a predetermined conclusion, we can also be motivated to be accurate. When we are accountable for our decisions and actions or when we decide in advance to focus on accuracy, we are much less likely to be simply find predetermined conclusions in the social realities that surround us. Deciding to be accurate might change the way that all of us interpret the entire situation and what it means for our country. While there is disagreement over what happened, why it happened, and what it all means, we can decide to let evidence and not our predispositions decide these questions.

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