People are characterized by different biological and psychological predispositions, reflexive patterns that can be overridden but that serve as important shapers of behavior. Liberals and conservatives consistently differ in everything from occupational preferences to leisure pursuits to sensitivity to disgust, as well as personality traits, moral foundations, personal values, culinary choices, and preferences for music, art, cars, humor, poetry, fiction, and neatness. So what does this have to do with politics? Bedrock political orientations—our knee-jerk gut reactions—naturally mesh with a broader set of orientations, tastes, and preferences because they are all part of the same biologically rooted inner self.
For example, the genetic basis of human flavor preference was discovered in 1931 by Arthur Fox, a chemist working for Dupont. As is so often the case with discoveries, it was in part an accident. Fox was pouring a powdered form of the compound PTC (phenylthiocarbamide) when some of the stuff became airborne. A colleague remarked that the PTC floating around the room tasted bitter. Fox was puzzled because he couldn’t taste a thing. He and his colleague started experimenting to see who could and could not taste PTC and found that some people were extremely sensitive to the taste, some could taste it but weakly, and some could not taste it at all. Later, researchers were able to establish that the ability to taste PTC is traceable to a couple dozen genes that shape individual variation in whether and how strongly PTC is tasted.
PTC taste strips are now a staple of grade school science classes designed to demonstrate variation in taste as well as the genetic basis of that variation. As plenty of science class alums can attest, those who can taste PTC generally experience it as a bitter flavor. This is interesting because those extremely sensitive to PTC also tend not to like vegetables that contain bitter secondary compounds such as those found in vegetables like broccoli and, yes, arugula. You can probably guess what is coming. Does PTC taste sensitivity systematically correlate with political ideology? One study empirically tested this on a group of undergraduates and found that conservatives are significantly more likely than liberals to detect PTC.
Interesting explanatory possibilities emerge. Food preferences are one of the nonpolitical traits that consistently differentiate liberals and conservatives. They are certainly shaped by culture and family but taste is also incontrovertibly rooted in biology. Taste buds, after all, are nothing more than chemical receptors and people differ markedly in the density and nature of these chemical receptors. It does not get more biological than that. The relevance of genes to taste further diminishes the attractiveness of the socialization argument, that the reason little conservatives hate broccoli is solely because they are taught to do so by their conservative, broccoli-hating parents, and raises an interesting question. Are genes relevant to tasting PTC merely linked to genes relevant to politics, or is the relationship more meaningful? But taste preference for a single compound, regardless of how genetically shaped, is likely to explain only a small amount of our culinary, let alone political, preferences. Besides, taste is only one sense. Variation in other senses is unlikely to connect to politics, right?
Evolutionarily speaking, our sense of smell is the most ancient and chemically direct of our sensory systems; its signals register more or less directly in the emotional centers of the brain. Olfaction encodes a great deal of information concerning what is good in our environments (the smell of a good meal) and what is bad (the smell of rot or decay). The smells we perceive are also known to carry a good deal of social information. For example, how attractive you are to the opposite sex depends partially on the olfactory compounds you are emitting, which is the basis of the $10 billion personal fragrance industry. Some of the social information wrapped up in a sense of smell relates not just to figuring out if someone is sexy but also to assessing their position in a social hierarchy, and this is getting close to politics.
Might variations in sense of smell be related to preferences for authoritarian or egalitarian social structures? In one of our own studies, we found evidence in support of such a possibility. An odor of great potential interest to social life is that emanating from androstenone, a steroid closely related to testosterone. Some people smell androsterone readily and report it to be overpowering; others cannot detect it at all. Further, among those who do smell it, there is variation in the odor’s appeal: Some say it smells like sweat or even urine, but others say it has a pleasant odor, like incense, sandalwood, or vanilla. A long-established and well-replicated connection exists between various forms of a particular gene and the ability to smell androstenone. We found that variations across people in the ability to detect the odor of androstenone predicts political attitudes such that those more sensitive to the odor of androstenone are also more comfortable with clear social hierarchies. We know that the world smells differently to some people than to others, and variations in the ability to smell androstenone might be related to political beliefs.
What makes conservatives and liberals so different? Our answer is that they experience and process different worlds. Biology predisposes people to certain preferences and tastes because individual differences extend to biology. We taste and smell the same things differently. We cognitively and subjectively interpret the same paintings or stories or jokes differently. We have different personalities, moral foundations, and personal values—and we have different politics. Conservatives and liberals are about as likely to persuade each other to different points of view as they are to persuade each other to have different reactions to phenylthiocarbamide or androstenone. They can, however, understand why those political differences exist. Understanding our differences will not lead to an end of political conflict, but it may lead to better management of political conflict.
Adapted from Predisposed: Liberals, Conservatives, and the Biology of Political Differences, Routledge Books, Sept 2013.