In Slate, Shankar Vedantam of the Washington Post informs us how Science explains why Juan Williams is made nervous by Muslims on flights:

We Are All Juan Williams Associating minorities with crime is irrational, unjust, and completely normal.

Juan Williams told Bill O'Reilly that he gets nervous at airports when he sees Muslims. For this, Williams has been roundly denounced as a bigot. But Williams' association between innocent Muslims and the perpetrators of the 9-11 attacks was less about bigotry–at least, bigotry conventionally defined–than about his mind working normally. To live in America in the post-9/11 age and not have at least some associations between Muslims and terrorism means something is wrong with you.

I am not suggesting that associating ordinary Muslims with terrorists is either rational or right. It's neither. But the association arises via a normal aspect of brain functioning, which is precisely why so many people entertain such beliefs–and why those beliefs have proved so resistant to challenge.

The left is wrong to wish the association away only by pointing out how unfair it is, because that denies the reality of how our minds work. The right is wrong to believe the association must be accurate merely because it is widespread.

See, it's all the fault of evolution:

Our ancestors constantly drew conclusions about their environment based on limited evidence. Waiting for causative evidence could have proved costly, whereas extrapolating causation from correlation was less costly.

The terrorist attacks of 9/11 were unusual. (Even if you take all the terrorist attacks in the world, they are still unusual.) In seeking explanations for those events, our minds are drawn to other unusual things linked to them–especially at the group level. ...

Muslims are only the latest victim of illusory correlations in the United States. African-Americans have long suffered the same bias when it comes to crime. In every country on earth, you can find minority groups that get tagged with various pathologies for no better reason than that the pathologies are unusual and the minorities are minorities.

Whenever people who strongly believe in illusory correlations are challenged about their beliefs, they invariably find ways to make their behavior seem conscious and rational. Those who would explicitly link all Muslims with terrorism might point to evidence showing that some Muslims say they want to wage a war against the West, that a large preponderance of terrorist attacks today are carried out by Muslims, and so on. This is similar to our longstanding national narrative about blacks and crime.

But even if blacks and whites do not commit crimes at the same rate, and even if Muslims are overrepresented among today's terrorists, our mental associations between these groups and heinous events are made disproportionately large by the unconscious bias that causes us to form links between unusual events and minorities. ...

People in Thailand will associate white American tourists with pedophilia even though many more acts of pedophilia are committed by Thais. But white Americans are a minority in Thailand, as are acts of pedophilia. So you will hear Thai people shout until they are blue in the face about individual anecdotes showing white Americans who are pedophiles. (The same is true of gay men and pedophilia in the United States.)

There's this obscure Thai cultural concept that might be helpful in understanding the irrational bigotry of Thais' views of single white male tourists in Thailand: it's called "on average."

Seriously, what we really need is an in-depth analysis of the systematic causes of anti-empirical bias in elite discourse.

The first is the professional deformation that journalists and fictional storytellers experience in their hunt for non-boring Man Bites Dog stories.You make more money coming up with interesting stories about anomalies than for pointing out the same old same old.

The second is the Platonic Temptation among intellectuals to think only in terms of absolute categories: e.g., Vedantam projects his own bias against thinking probabilistically when he claims, without citing any evidence, that there are "Those who would explicitly link all Muslims with terrorism..."

The third is The Smartest Guy in the Room Syndrome: the presumption that the more moving parts and unlikely assumptions in your theory, the smarter you must be to hold it all together in your head, so, therefore, you win.