Here's the original article in the Boston Globe.
The DSM IV defines delusions as false beliefs based on incorrect inference about external reality that persist despite the evidence to the contrary.
And what did this recent University of Michigan Study find about political bias?
In a series of studies in 2005 and 2006, researchers at the University of Michigan found that when misinformed people, particularly political partisans, were exposed to corrected facts in news stories, they rarely changed their minds. In fact, they often became even more strongly set in their beliefs. Facts, they found, were not curing misinformation. Like an underpowered antibiotic, facts could actually make misinformation even stronger.
This bodes ill for a democracy, because most voters — the people making decisions about how the country runs — aren’t blank slates. They already have beliefs, and a set of facts lodged in their minds. The problem is that sometimes the things they think they know are objectively, provably false. And in the presence of the correct information, such people react very, very differently than the merely uninformed. Instead of changing their minds to reflect the correct information, they can entrench themselves even deeper.
These findings open a long-running argument about the political ignorance of American citizens to broader questions about the interplay between the nature of human intelligence and our democratic ideals. Most of us like to believe that our opinions have been formed over time by careful, rational consideration of facts and ideas, and that the decisions based on those opinions, therefore, have the ring of soundness and intelligence. In reality, we often base our opinions on our beliefs, which can have an uneasy relationship with facts. And rather than facts driving beliefs, our beliefs can dictate the facts we chose to accept. They can cause us to twist facts so they fit better with our preconceived notions. Worst of all, they can lead us to uncritically accept bad information just because it reinforces our beliefs. This reinforcement makes us more confident we’re right, and even less likely to listen to any new information.
There is a substantial body of psychological research showing that people tend to interpret information with an eye toward reinforcing their preexisting views. If we believe something about the world, we are more likely to passively accept as truth any information that confirms our beliefs, and actively dismiss information that doesn’t. This is known as “motivated reasoning.” Whether or not the consistent information is accurate, we might accept it as fact, as confirmation of our beliefs. This makes us more confident in said beliefs, and even less likely to entertain facts that contradict them.
New research, published in the journal Political Behavior last month, suggests that once those facts — or “facts” — are internalized, they are very difficult to budge. In 2005, amid the strident calls for better media fact-checking in the wake of the Iraq war, Michigan’s Nyhan and a colleague devised an experiment in which participants were given mock news stories, each of which contained a provably false, though nonetheless widespread, claim made by a political figure: that there were WMDs found in Iraq (there weren’t), that the Bush tax cuts increased government revenues (revenues actually fell), and that the Bush administration imposed a total ban on stem cell research (only certain federal funding was restricted). Nyhan inserted a clear, direct correction after each piece of misinformation, and then measured the study participants to see if the correction took.
For the most part, it didn’t. The participants who self-identified as conservative believed the misinformation on WMD and taxes even more strongly after being given the correction. With those two issues, the more strongly the participant cared about the topic — a factor known as salience — the stronger the backfire. The effect was slightly different on self-identified liberals: When they read corrected stories about stem cells, the corrections didn’t backfire, but the readers did still ignore the inconvenient fact that the Bush administration’s restrictions weren’t total.
It’s unclear what is driving the behavior — it could range from simple defensiveness, to people working harder to defend their initial beliefs — but as Nyhan dryly put it, “It’s hard to be optimistic about the effectiveness of fact-checking.”
So to bring the point home, here's the definition of Delusional Disorder from the DSM-IV:
Delusional disorder is an illness characterized by the presence of nonbizarre delusions in the absence of other mood or psychotic symptoms. Delusions are false beliefs based on incorrect inference about external reality that persist despite the evidence to the contrary.