(Note: by "libertarian" I refer to the princples and ideals of free-market and limited government, not the political party. As Duverger's Law describes, political third-parties are neither practical nor sustainable.)
As one of my favorite thinkers, Ayn Rand, so often repeated: There is one objective reality. That means we human beings interpret and perceive reality, and when two people disagree... one person is right, the other is wrong. Morality is a not objective, since it deals with personal values. For example, people disagree whether it's "wrong" to eat an animal or abort a fetus. However, economics is objective. When the price of wheat doubles, it has very concrete and measurable effects on goods and people. When there are economic disagreements, one person is right and the other is wrong.
When I get into a political discussion with someone, if they say "I value helping the poor." Then I would say "Me too. Great, but are you okay with erasing personal property rights to do that? Are you okay with trusting state bureaucrats to administer such basic human traits as empathy and charity? Are you okay with diminishing labor incentives by rewarding the unemployed for doing nothing? " If they said "Yes.", I would walk away disgusted at the looter. If they said "No, but-"... it'd be an example of the ignorance and contradiction that is socialism. Based on many debates and discussions with people, I've come to one simple conclusion: capitalists, fiscal conservatives and "libertarians" are smarter.
Socialists are often called "bleeding-heart liberals", which suits them because they jump to emotional reactions without critically and rationally reasoning the effects of their policies. "Leftists" are often found in fields like humanities and literature. I've found that many verbose intellectual types lean left. Word-smithing journalists and sociology professors lean left. Both types love to hear themselves talk. They thrive on demagoguery posing as moral crusaders to the masses.. Their egos tell them they aren't rewarded enough, feeding their bitterness towards the rich. (Sociology and English professor careers depend heavily on government education/tuition subsidies as well.)
I've noticed some general habits of "leftists" from debating them. They argue with emotion, guilt, and scapegoating. They are quick to call free-market purists "racists" or "wacko". When confronted with concrete examples, they seem to retreat into red herrings and complexity (e.g. Keynes). This stereotype was captured by the Atlas Shrugged character Dr Simon Pritchett, who proclaimed in Kant style "the duty of thinkers is not to explain, but to demonstrate that nothing can be explained.". Another amusing stereotype is the sloppy leftist vs. the orderly conservative. I imagine frizzy haired socialists tossing junk in the back seat of their bumper sticker plastered car. Stereotypes aside, those who deal with emotion instead of rationality will be uncomfortable with hard rules and principles. Libertarians (and true conservatives) respect principles and strict property rights, because they understand the danger of leaving policy and law to the whim of those in power.
So, whether one calls it "smarter"... or simply more disciplined in critical thinking on economic issues, the free-market supporters are superior. If the grand economic experiment of USSR vs. USA didn't convince socialists, nothing will. I'm not the first to discuss this subject. John Ray (M.A.; Ph.D.) also discussed how egoism of academic-types makes them lean left He also points out: "Libertarianism is far and away the most common political orientation among Mensans." (the group with IQ in top 2%). Another blogger and Half Sigma discussed how those who oppose government intervention score better on Wordsum. A recent New York Times op-ed discussed findings that “those taking more economics classes favored less regulation or government intervention affecting prices for specific goods and services, including wages and salaries.”. Another recent WSJ op-ed discussed a test of economic propositions, where: "Democratic averaged 4.59 incorrect answers. Republicans averaged 1.61 incorrect, and Libertarians 1.26 incorrect".
Perhaps my favorite relevant link is an old 1992 libernet post by Stuart Reges, entitled "Libertarian IQ". I agree with his sentiments that libertarian-type thinking is frequently found among engineers and computer scientists. Having studied and worked in this field, I often just assume that my colleagues share my political inclinations. Like Stuart suggested, one cannot succeed in this field unless they are capable of challenging mental and cognitive tasks... visualizing how a system will work at both a high-level and a low-level, how the parts interact, perform, and affect one another from their inputs and outputs. I would predict that those who cannot design a good system, would also be likely to believe something like ObamaCare will fix our health care system.