This week a horrible tragedy occurred at Ft. Hood army base. According to the news reports, an army major went on a shooting spree. In the period since the news broke, a consistent focus of discussion has been: Why did he do it? News reports list aspects of his life in articles titled “Motive Probed” and “Details Emerge about Suspect Background”. The writers have noted that he was Muslim, that he was to be deployed and did not want to go, that he had treated traumatized soldiers and may have suffered because of that, and that he was quiet. In the next few days other aspects of his past, and of the event, will come to light. The rush to find an explanation highlights a common aspect of human reasoning.
Different people will focus of different features to explain why he did it. Some people will note that he was Muslim and thus may have been a terrorist. Others will focus on his treating PTSD soldiers and on the issues of secondary trauma potentially contributing to his problems. Still others will find other features.
These discussions will tell us more about the beliefs of the people talking than the actual motive of Major Hasan. A confirmation bias occurs when a person has a belief system, looks at a new situation, and focuses on evidence consistent with their pre-existing belief system. They most likely ignore other aspects of the situation that suggest contrary explanations. They ignore other evidence that suggests these supposedly causal factors may not be the actual cause. People see and remember what they expect to see.
Major Hasan, like all people, was undoubtedly a complex individual. Because of this, there will be a variety of factors in his life on which many people can seize as being the cause of his violent outburst. In focusing on one aspect, we ignore the other factors that may have contributed to this catastrophe. In addition, we are forced to ignore other evidence that contradicts our position. In particular, people must ignore whether that one particular aspect predicts the outcome – What Cognitive Psychologists call base rate information. In other words, how often do people with those features not engage in such actions and do people without those features engage in those actions? With respect to this shooting rampage, people may focus on his Muslim religion as contributing. They argue that religion predicts violence. To do this, they must ignore the fact that most Muslims do not engage in such actions and some non-Muslims have also gone on shooting sprees. Similarly, if people focus on his work with traumatized soldiers, they must ignore that other people do similar work without violent ramifications.
My point is relatively simple. The causes of any person’s behavior in any particular context is always complex. People who quickly focus on some aspect of a complex situation may be displaying a confirmation bias. They may tell the rest of us more about their own belief system and biases than anything else.
