As it so often does, the GSS allows us to put this theory to a general test by tapping data that was not specifically designed to measure what Haidt and company are after but that, conveniently, still manages to provide another measurement.
I've selected six items, each one approximating one of the six foundations, and compared average liberal and average conservative responses to them in standard deviations. Positive (negative) values indicate that conservatives care more (less) about assuring the positive expression of the foundation is condoned and/or the negative expression of the foundation is censured than liberals do.
The care/harm question asks respondents if they believe the government should help pay for medical expenses for those who cannot afford them; the fairness/cheating question asks if it is wrong for a person to hide income to avoid paying taxes; the liberty/oppression question asks if personal freedom is more important than marriage; the authority/subversion question asks if a cop is ever justified in hitting a citizen; the sanctity/degradation question asks if gay sex is immoral; and the loyalty/betrayal question asks if a person should support his country even if when it is acting in the wrong:
The GSS results largely support Haidt's divisions, with liberals putting greater emphasis on liberty/oppression and especially care/harm, just as he found to be the case. Conservatives, on the other hand, are more concerned with fairness/cheating, authority/subversion, sanctity/degradation, and loyalty/subversion than liberals are. With the exception of the authority/subversion item, for which moderates and liberals are virtually indistinguishable, moderates fall in between liberals and conservatives on every foundation.
The gap between liberals and conservatives on fairness/cheating is larger than expected in the GSS relative to Haidt's findings on authority/subversion and loyalty/betrayal, and the sanctity/degradation gap is probably even wider than Haidt would expect it to be, but these questions are by no means perfectly calibrated to replicate his approach--the fact that they follow the overall pattern described by the moral foundations theory suggests it has descriptive value. Whether it is especially useful or overly cute and stylized is perhaps a separate issue, but that's not the point of this post.
Haidt has a simple, free site for those interested to gauge their own moral foundations within the framework of his theory, though it combines the fairness/cheating and liberty/oppression aspects into a single foundation on which liberals place greater importance.
My results (in green):
Mostly in line with conservatives on four of the five, my only deviation being on the sanctity/degradation foundation (which is, confusingly, referred to as "purity" in the online survey). Engaging in a little self-reflection, my results capture what sometimes borders on indifference towards the plight of others and also what they choose to do to themselves, and the high expectations of loyalty from friends, family, and colleagues. The purple would've suited me nicely, I think!
GSS variables used: HELPSICK, TAXCHEAT, MARFREE, POLHITOY, HOMOSEX, IFWRONG, POLVIEWS(1-2)(3-5)(6-7)