In all the outrage over Donald Trump's outrageous suggestion to keep Muslims out of the United States, a proposal repugnant to most but supported by millions, there has been little comment on what makes such overt bigotry so popular. It's true that "paranoia is overriding reason", as Tom Brokaw suggested. But that only observes what's happening. It doesn't explain it. The more important question is why, whenever we are afraid, does fear so readily trump (sorry) reason? We need to understand these root causes in order to protect ourselves against the dangerous mistakes we sometimes make even as we try to make ourselves safer.
The most important answer comes from decades of research into human cognition that has found that we're just not as smart as we think we are. Psychologist Daniel Kahneman and many others have found that a lot of how our brains produce our perceptions and behaviors is subconscious and instinctive. Much of our 'thinking' happens outside the realm of conscious reason, and beyond its control. As satirist Ambrose Bierce said in the Devil's Dictionary, the brain is only the organ with which we think we think.
Neuroscience has found that our brain is wired to give the upper hand to instinct and emotion. As Joseph LeDoux, a pioneer in the neuroscience of fear, put it in The Emotional Brain, "...the wiring of the brain at this point in our evolutionary history is such that connections from the emotional systems to the cognitive systems are stronger than connection from the cognitive systems to the emotional systems." It might not be rational to fear more and reason less, but that's just how the brain works.
Research on the psychology of risk perception by Paul Slovic and others has found that some threats feel scarier than they actually are because of their nature, regardless of the numbers. The statistical likelihood of being a victim of terrorism is infinitesimal, but when something bad happens to people like us - for westerners that means terrorism victims in Paris more than in Beirut; for Americans, it means victims in San Bernardino more than in Paris - we feel like that same harm could happen to us, which makes us worry about that risk, regardless of the odds. And we don't know what we need to know to protect ourselves from terrorists, since we don't know when or where or how we might be attacked by whom. That feeling of powerlessness and vulnerability raises the fear as well.
But how does fear lead us to demonize whole groups of people based on the actions of a few? Social psychology has found that when we are worried we tend to band together into groups...tribes, if you like. After all, as social animals, humans have evolved to rely on our tribes for our own safety and survival. When we face a threat we can't protect ourselves from as individuals, we metaphorically circle the wagons, and anyone inside our circles - those who share our race or gender or nationality or socioeconomic class or religion or general beliefs and values - is friend, and anyone outside those circles is foe. It feels reassuringly safe to be inside the protective circle. This instinctive subconscious cultural cognition powerfully overwhelms cool calm objective reason.
These sobering realities about the limits to objective reasoning help explain why Donald Trump's fear-mongering racism is so resonant to so many (two thirds of likely Republican primary voters.) They explain the bigoted calls of Jeb Bush and Marco Rubio to ban immigrants from some Middle East countries unless they are Christians. They explain the rise of anti-immigrant parties in France, the Netherlands, Italy, Austria, Hungary, and Switzerland, groups that are circling the wagons and demonizing 'others' as the enemy.
And they explain the long human history of hateful, destructive behavior committed in the name of fear, and why we can't learn from that history, and why even when such bigotry is likened to the Nazi genocide or the U.S. internment of Japanese-Americans during the fearful days of World War II that can't counteract the racism that Trump supporters are relying on for their sense of safety and protection.
The good news is that the bigotry of Tribe Trump is being soundly rejected, (more than half a million people have signed a petition to ban Trump from entering England) and for the same psychological reason. It's not as the vast majority of people offended by Trump's bigotry aren't also afraid of terrorism. They are. But they find reassuring solidarity by identifying with the larger tribe whose moral values reject racism and bigotry as repugnant. And those people also share a fear of how Trump's bigotry plays right into the hands of terrorists and incites more violence. The Mayor of St. Petersburg has banned Trump from entering that community "until we fully understand the dangerous threat posed by all Trumps." (my emphasis)
We can't undo these instincts. That fear overwhelms reason is simply built into human nature. But there is value in recognizing why this happens. Understanding why paranoia overrides reason can help us recognize when we are overreacting to a threat that feels scary but doesn't actually threaten most of us. That can help us temper that overreaction and try to minimize the dangers it can produce, including the dangers from bigotry and tribal divisiveness that does all sorts of harm all by itself.