What makes a person liberal or conservative?

In today's Wall Street Journal, Arthur Brooks (subscription required) explains how conservatives and liberals differ. An excerpt:

While just about everybody -- left and right -- agrees that poverty is unacceptable (although policy makers disagree as to whether a minimum wage hike would help or hurt the working poor), conservatives do not share liberals' concern about income inequality. According to the 2005 Maxwell Poll on Civic Engagement and Inequality, self-described liberals are more than twice as likely as conservatives to say income inequality in America is a "serious problem." And while 84% of liberals think the government should do more to reduce inequality, only 25% of conservatives agree.

This is empirical substantiation for the old cliché that conservatives just don't care about the poor, right? Wrong. In fact, the data do not tell us that conservatives are uncaring; they actually tell us that conservatives are optimists. Conservatives are relatively untroubled by inequality, and unsupportive of government income redistribution, because they believe the American economy provides private opportunities to succeed. Liberals are far more pessimistic than conservatives about the possibility of a better future for Americans of modest means.

Consider the evidence. While 92% of conservatives believe that hard work and perseverance can help a person overcome disadvantage, only 65% of liberals think so. This difference of opinion, contrary to the convention, is not because conservatives earn more money. In fact, lower-income conservatives are about twice as likely as upper-income liberals to say they think there's "a lot" of upward mobility in America. If a liberal and a conservative are exactly identical in income, education, sex, family situation, and race, the conservative will be 20 percentage points more likely than the liberal to say that hard work leads to success among the disadvantaged.

These observations ring true to me.

I wonder to what extent a person's answer to these questions is in part a function of personal family history. Most likely, I unconsciously overestimate economic mobility because my family has gone from near the bottom to near the top of the income distribution in two generations. My successful friends who come from wealthy families (who are usually more liberal than I am) may well do the opposite--unconsciously overestimate the extent to which family background made their successes inevitable. Psychologists tell us that people tend to overweight salient observations when making decisions. There is no observation more salient than a person's family history.