Dr. Michael Shermer is the author of "Why People Believe Weird Things." He is the publisher of Skeptic Magazine and the Presidential Fellow at Chapman University, where he teaches Skepticism 101.

The new year has brought us the apparently new phenomena of fake news and alternative facts, in which black is white, up is down, and reality is up for grabs.

The inauguration crowds were the largest ever. No, that was not a “falsehood,” proclaimed by Kellyanne Conway as she defended Sean Spicer’s inauguration attendance numbers: “our press secretary…gave alternative facts to that.”

George Orwell, in fact, was the first to identify this problem in his classic Politics and the English Language (1946). In the essay, Orwell explained that political language “is designed to make lies sound truthful” and consists largely of “euphemism, question-begging and sheer cloudy vagueness.”

But if fake news and alternative facts is not a new phenomenon, and popular writers like Orwell identified the problem long ago, why do people still believe them? Well, there are several factors at work.

Cognitive simplicity

In general, when our brains process information belief comes quickly and naturally, skepticism is slow and unnatural, and most people have a low tolerance for ambiguity. Research shows that when we process and comprehend a statement our brain automatically accepts it as true, whereas the subsequent skepticism of the statement requires an extra cognitive step, which is a heavier load to lift. It is easier to just believe it and move on.

fMRI brain scan research shows that when we understand a statement we get a hit of dopamine in the reward areas of our brain, in which comprehension is positively rewarded and feels good. By contrast, the brain appears to process false or uncertain statements in regions linked to pain and disgust, especially in judging tastes and odors, giving new meaning to a claim “passing the taste test” or “passing the smell test.”

Cognitive dissonance

Cognitive dissonance is the uncomfortable tension that comes from holding two conflicting thoughts at the same time. It’s easier to dispute the facts than to alter one’s deepest beliefs. Creationists, for example, challenge the evidence for evolution not for scientific reasons but because they fear that if the theory is true they have to give up their religion. Climate deniers don’t dispute the data from tree rings, ice cores, and the rapid increase of greenhouse gases out of scientific curiosity – but because they’re afraid that if it’s true it might mean more restrictive government regulations on business and industry.

Backfire Effect

Cognitive simplicity and dissonance leads to a peculiar phenomena in which people seem to double down on their beliefs in the teeth of overwhelming evidence against them. This is called the backfire effect. In a series of experiments by the Dartmouth College, subjects were given fake newspaper articles that confirmed widespread misconceptions, such as the existence of WMDs in Iraq.

When subjects were then given a corrective article that WMDs were never found, liberals who opposed the war accepted the new article and rejected the old, whereas conservatives who supported the war did the opposite. And more: they reported being even more convinced there were WMDs after the correction, arguing that this only proved that Saddam Hussein hid or destroyed them. In the real world, when WMDs were not found, liberals who supported the war declared that they had never supported the war, and conservatives who supported the war insisted there were WMDs.

Tribal unity

We are a social primate species and we want to signal to others that we can be trusted as a reliable group member.

This means being consistent in agreeing with our other group members—whether that group is our political party or our religious faith—that we will not stray too far from our group’s core beliefs.

Thus, cognitive simplicity and cognitive dissonance may have an evolutionary adaptive purpose, as the social psychologist Carol Tavris outlined it in an email to me:

“When you find any cognitive mechanism that appears to be universal—such as the ease of creating ‘us-them’ dichotomies, ethnocentrism (‘my group is best’), or prejudice—it seems likely that it has an adaptive purpose; in these examples, binding us to our tribe would be the biggest benefit.In the case of cognitive dissonance, the benefit is functional: the ability to reduce dissonance is what lets us sleep at night and maintain our behavior, secure that our beliefs, decisions, and actions are the right ones. The fact that people who cannot reduce dissonance usually suffer mightily (whether over a small but dumb decision or because of serious harm inflicted on others) is itself evidence of how important the ability to reduce it is.”

Ultimately we are all responsible for what we believe and it is incumbent on us to be our own skeptics of fake news and alternative facts. When in doubt, doubt.

Ask “how do you know that’s true?” “What’s the source of that claim?” “Who said it and what is their motivation?” We must always be careful not to deceive ourselves, and we are the easiest people to deceive. As George Orwell wrote in a poignantly titled 1946 essay In Front of Your Nose:

“To see what is in front of one’s nose needs a constant struggle. … The point is we are all capable of believing things which we know to be untrue, and then, when we are finally proved wrong, impudently twisting the facts so as to show that we were right. Intellectually, it is possible to carry on this process for an indefinite time: the only check on it is that sooner or later a false belief bumps up against solid reality, usually on a battlefield.”

Other books by Dr. Michael Shermer include "Why Darwin Matters," "The Science of Good and Evil," and "The Moral Arc." His upcoming book is "Heavens on Earth: The Quest for Immortality and Perfectibility." Follow him on Twitter @michaelshermer.