In the current political environment, the divide between us seems acutely apparent. To better understand how it’s so easy for us to see and understand important issues so very differently, we must look at the biological roots of discord—how we build our memories and beliefs about the world. I think we can all agree that memories are constructed out of past experiences. But it’s a common misconception that memory is primarily attributable to perceptual inputs. If this were the case, why can two people see the same issue from such divergent perspectives? There’s no doubt that our sensory experiences are the stuff of most of our stories about the past. But we suggest that experience, and hence the stories we tell about past events and to describe the world we live in, are fundamentally not a perceptual affair. An interpretative process essentially determines experience and our memories 

In many respects, the fact that we attend to certain stimuli and disregard others is an adaptive response to our environment conditioned by our brain’s processing limitations. There are up to 40 million data points available to our brains from both the external environment and within our body at any moment in time. That’s a large number, and if we were to take in all 40 million bits of data in one gulp, our brains would be overloaded and either shut down or explode. You see, our conscious brains can only process about 120 bits per second, according to Mihaly Csikszentmihalyi and Bell Labs engineer Robert Lucky.i This discrepancy between the available data and our minds’ speed limits sets up an interesting quandary for us. What should we pay attention to? And how do we decide? 

As you might expect, it’s a complicated issue. Just listening intently to one person requires that we process nearly 60 bits of information a second. Listening to two people puts us right up against our processing limit. Forget about listening to three people talking simultaneously or following four friends’ conversation in a noisy restaurant. Talking to someone coherently while also attempting to text is virtually impossible. Driving and texting at the same time are comparable in attention degradation to knocking back a couple of martinis before getting behind the wheel of the car. Concerted listening to and comprehending the world of another requires total concentration. Even then, two people listening to the same person talking can easily walk away from that conversation with very distinct conclusions about what was said, what it meant, and what the speaker’s intentions were. 

How do we cope with these physical limitations? We become very selective regarding the things we attend to. That’s where interpretation comes in. Here’s a brief example to highlight the issue. Imagine you’re a woman looking into the eyes of your beloved over a candlelit dinner in a fine French restaurant. At the table next to you, two guys are debating the likelihood that your hometown team will make it into the playoffs. If you’ve never even been to a football game in your life and lack any appreciation for the sport’s intricate rituals and rules, their conversation will be like white noise to your ears. Even if they’re speaking at a sufficient decibel level that you can physically hear them, it no doubt wouldn’t matter. If someone asked you later that evening what they were discussing, you’d probably have no idea given how absorbed you were in what your lover had to say.  

Your lover, on the other hand, may have had an entirely different experience sitting across from you. While he genuinely adores you, his ear catches a bit of the conversation at the next table. He immediately wondered if he made a wise decision on the bet he made with a good friend in Chicago. Spotting him 6 points on a $500 wager is beginning to seem foolish, and that’s money he won’t have after paying this evening for the bottle of expensive wine, the Crème brûlée, and a pousse-café with brandy. Now he goes down that rabbit hole, regretting his decision, suddenly feeling a chill as worry spreads from his forehead to his toes. What was he thinking when he gave his friend 6 points? All the while, he’s smiling and looking lovingly into your eyes. You ask him an important question, but he is caught off guard because he had unconsciously chosen to split his attention. He gives you a perplexed look. Sorry, he says, I didn’t catch all of that because of all of the noise in here. You begin wondering whether he’s heard anything you had to say for the past ten minutes. Now, he’s sailing in dangerous waters, all because of his brain’s incapacity to listen to you and the football junkies at the same time 

Csikszentmihalyi refers to this phenomenon as an attentional filter. Most of the time, it’s a boon to our functioning in the world. For the most part, these interpretational filters work unconsciously, screening out all kinds of perceptual data that our mind deems to be irrelevant to the task at hand. That’s’ why, when you’ve been driving on the freeway for several hours at a stretch, you don’t remember much of the scenery that has whizzed by: Your attentional system protects you from registering it because it isn’t deemed important. Things our brain considers essential, we’ll let into our perceptual field. Our minds automatically screen out matters it interprets to be lacking relevancy.  

While having a filtering mechanism of this sort helps us function in the world, there are some decided disadvantages. Once an interpretational filter is in place, our receptivity to new information becomes completely impaired. We can miss vital clues and evidence pertinent to our interests or survival in this condition, even if they’re staring us in the face. Just as our gentleman in the restaurant directed his attention based on his interests and concerns, all of us are continually interpreting what is valuable for us and what we can let slide. This is a perfect mechanism to create a chasm of misunderstanding between our world and another person who has constructed an entirely different story from the same raw data. That’s in part why a Democrat and a Republican could each watch one of the recent presidential debates and arrive at really different judgments about who won and why. This issue gets amplified when two people live in distinct worlds—hence the discrepancy between how people in America’s heartland and urban dwellers see the world. Perhaps the more important question is, how can we consciously manage our idiosyncratic filters to understand ourselves and others better?