Our genes are like tiny little blueprints. Eye color is determined by a single gene. More complex features involve several to many genes. Genes are involved throughout our lives, both in building us and operating us. Scientists may be busy mapping genes to traits until we stop doing medical research.
It seems far-fetched to think of genes that would make you a Democrat or a Republican, but there is persuasive evidence that many behavioral and affective traits are heritable. Among traits that are at least partly heritable are intelligences, school achievement, creativity, reading ability, and mental retardation. Also schizophrenia, affective disorders, alcoholism, anorexia, Tourette’s syndrome, and Alzheimer’s disease. Some attitudes are also known to be partially heritable.
The total variability in a trait is the sum of genetically-associated variability and all other variability, which is environmental and experiential. The heritability of a trait is the portion of total variability in the trait that is associated with variation in the involved genes. It runs from zero to one hundred percent.
The two portions of variability can't usually be estimated through knowledge of the genes and their functions. One limitation to that approach is that our knowledge of genes and their roles is incomplete. Another limitation is that, even if we have full understanding of the genetics of a trait, we must also know how much it varies due to environmental and experiential effects.
We can estimate both types of variability if we know the genetic similarity of subjects and whether they have experienced the same or different environments. We know how genetically-similar unrelated people are. We know that identical twins have identical genes. Fraternal twins and other siblings share on average half their genes. On the experience/environment dimension we can compare people who have grown up in the same household to people who grew up separately. Growing up in the same family isn't growing up with identical experiences, but it is close enough to allow reasonable estimates of heritability.
Twins who grow up together in the same family also grow up at the same time, so they are likely to have more similar experiences than other pairs of people. Twin studies provide the most powerful way to estimate the heritability of complex traits and behaviors. Some states maintain twin registries that are available to researchers. When identical twins are raised in different families, differences in their attitudes must be due mainly to the effect of life experiences.
Another way to estimate heritability compares natural siblings with adopted unrelated siblings. Natural children share, on average, half of the genes in our genome that are variable. Adopted children share a much smaller part.
Using studies based on these facts, estimates can be made of how much influence heredity and environment/experience have on attitudes. Studies have found significant heritability in attitudes such as aggressiveness and altruism, attitudes toward alcohol but not toward coffee or tobacco, and even TV-watching time among preschool children. A wide range of psychological traits are believed to be heritable, although how and why they are heritable is not well understood in detail.
In many of these cases, the specific genetic influence on the trait is not known, and several or many genes may be involved. While eye color seems to be controlled by a single gene, attitudes are not. Tesser suggests a variety of genes that could affect an attitude. Hormones influence temperament, and are known to be influenced by various genes. Intelligence, which is comprised of a number of components, is heritable. To the extent that the formation and maintenance of attitudes involves cognition, heritable intelligences should affect those attitudes. Heritable metabolic activity level could affect attitudes. More speculatively, there may be heritable differences in how we respond to conditioning (reward or punishment). Individuals who are more sensitive to punishment might be more risk-averse in considering choices practical and theoretical, and this may be a heritable characteristic.
Studies from 1973 and 1986 estimated a heritability of almost 50% in the answers to two series of questions which were thought to suggest a conservative attitude. In other words, these aren't RWA (right wing authoritarianism) or SDO (social dominance orientation) questions. In both those studies, subjects were presented with statements that they were asked to agree with (“Yes”), disagree with (“No”), or be ambivalent about (“?”). The five items that were most heritable from each study follow:
From the 1973 study:
From the 1986 study:
These items are different from the items found in the definitional RWA and SDO scales, and some of them measure traits that today are considered different but related. Nevertheless, they are consistent with conservatism/liberalism. The “Jazz” item was meant to measure a general discomfort with ambiguity or complexity that is believed to be present amongst conservatives. Kenny G. hadn't been heard from yet. You may question to what degree each of these questions is related to the types of conservatism you’re familiar with, but together (along with the thirty items I haven’t listed) they make at least a sketch of conservatism. They illustrate the types of attitudes that have been found strongly heritable.
Heritability is the ratio of genetically-caused variation (which can be considered fixed) to total variation (which includes environmentally-attributed variability, and is not fixed). Estimates of heritability are dependent on the variability of the environments that have been experienced by the subjects. You’d get a different answer if you studied children raised by wolves, or fifth-century BCE Spartan noblekids. Some interpretations of heritability must assume a more-or-less fixed range of environmental and experiential history.
In his 1993 study Tesser looked further into the significance of the heritability of attitudes that are related to left-right political orientation. He found that heritability has important further consequences. A heritable attitude by its nature is resistant against variations in environment and experience.
Tesser found that more-heritable, less-learned attitudes are accessed more quickly than less-heritable, more-learned attitudes. He demonstrated this by timing subjects’ responses (“Yes”, “?”, “No”) to the attitude items. He adjusted for the length of the text, which affects comprehension speed. Other psychological and linguistic research tells us that more-quickly-accessed ideas are also accessed more frequently and with less reflection.
Behaviors, which are to some extent the products of attitudes, are often affected by the social environment. Tesser found that the behavioral expression of more-heritable attitudes is more difficult to affect by social input than the expression of less-heritable attitudes.
Attitudes serve a variety of our psychic needs. Attitudes are believed to help us to protect our self-concepts, to help us function effectively inter-personally, and to help clarify us to ourselves. It is easier and more comfortable to relate with those who share our attitudes. Tesser found that we are inclined to weigh more-heritable attitudes more heavily in choosing who to socialize with than we weigh less-heritable, more-learned attitudes. Tesser’s study evaluated this in a context that involved choosing opposite-sex individuals as friends, romantic partners, or spouses, and found roughly the same effect in each of these scenarios. (It's likely that the same effect applies to same-sex companions.)
So the heritability of ideological attitudes contributes to their durability and to the great ideological divide.
Next: Conservative Conspiracies
More information:
[Tesser 1993] “The Importance of Heritability in Psychological Research: The Case of Attitudes,” Abraham Tesser, “Psychological Review,” Vol. 100, 1993.
© 2021, Ross A. Hangartner