I have had the following experience many times, and so I suspect that it is a near-universal experience. You are in a heated conversation with one or more other people who have differing opinions on the topic of discussion. Perhaps it’s just a fight over personal matters. After the heat has died down and calmer emotions prevail, you try to come to some sort of resolution about the prior conversation. Such efforts, however, are complicated by the fact that everyone has a very different memory of the conversation you just shared.

A related experience that is also common occurs when discussing a topic about which there is disagreement (such as politics), and then revisiting the topic weeks or months later. Again, everyone has a different memory of the prior discussion, including which facts were established. It’s almost as if the previous conversation had not taken place.

It’s as if everyone edits their memories to fit their existing narrative. In this way, memory can be a very dangerous thing – it gives us a false confidence in our current beliefs and attitudes. We believe the facts support our position. However, we often choose our facts based on our narrative, rather than craft a narrative based upon facts.

We tend to easily see this process in others, but of course often fail to see it in ourselves.

As an aside, this is perhaps one of my favorite aspects of the internet, combined with smartphones. Now, during a conversation and in real time, I can look up a reference to establish a fact, rather than just relying on everyone’s edited memories.

A newly published study sheds further light on this common experience of dueling memories. The researchers wanted to explore the effect of in-group vs out-group status on memories of wartime atrocities. Specifically, they looked at memories of stories of atrocities committed by either American or Afghan soldiers.

Subjects were given written stories about atrocities committed by either side, including a justification for their actions. After a distraction period they then watched a video in which some of the stories were repeated, but without the justification. Following another distraction period they were then asked questions about the stories.

As predicted by the researchers, Americans were more likely to remember the justifications for the actions of American soldiers than they were for Afghan soldiers.

Previous research has clearly established that humans are tribal – we think in terms of in-group and out-group. We can show tremendous altruism and compassion towards members of our in-group, while simultaneously displaying callous cruelty toward members of an out-group. History provides many examples – in extreme cases out-groups can be entirely dehumanized, allowing for unlimited cruelty.

Another way to look as this is through cognitive dissonance. It is likely that many Americans have a narrative that we are the good guys and the Taliban are the bad guys. A story about American atrocities is at odds with that narrative, causing cognitive dissonance, while stories about Afghan atrocities is compatible with our narrative. The cognitive dissonance is relieved by a justification for the bad behavior – they had to torture that captured soldier because he had information about an upcoming attack which could harm civilians.

It makes sense that we would hold onto those cognitive dissonance-relieving facts and remember them. Meanwhile, justifications for the behavior of the other guys is of no emotional value, and in fact may cause a bit of cognitive dissonance, depending on how strong our narrative is about them being the bad guys.

All of this gets filed under the general phenomenon of confirmation bias – we tend to notice and remember details that support our existing narrative, and miss, forget, or explain away details which contradict our existing narrative.

So we have cognitive dissonance, confirmation bias, in-group-out-group bias, and selective memory all conspiring together in this study.

The important thing to keep in mind is that this is our everyday experience. Such biases and more are in effect at all times, and not just in other people, but in ourselves (that is the hardest thing to remember). Just knowing that such biases exist is helpful, but not sufficient to erase their influence (that rationalization is particularly insidious).

It takes effort and cognitive work to step back from our immediate reactions and analyze our thought processes for potential bias. Psychologists call this metacognition – thinking about thinking. It can, and should be, a life-time project.