Thinking about Incest 4: Getting more Explicit about the Westermarck Effect

In previous posts in this series, I talked about genetic sexual attraction, incest, and some current characterizations of the Westermarck Effect. In this post, I want to offer a preliminary sharpening of the Westermarck Effect, based just on those previous characterizations. The most natural reading of them might give us something like this as an expression of the effect named for Westermarck:

if two individuals are intimate childhood associates, having been raised together for a number of years from early in life, then those two individuals will have a psychological aversion to sexual relations to one another and/or will lack erotic feelings for one another, and will, as a result, avoid incestual behaviors with one another when they are sexually mature.

This formulation makes intimate childhood association, however it is spelt out precisely, a sufficient condition for a cluster of attitudes, feelings, and behavior avoidances. It can also be read as making both predictions—from childhood facts to claims about adulthood—and retrodictions—from adulthood facts to claims about childhood–about attitudes, feelings, and behavior avoidances in particular individuals, and to posit a causal chain linking early life experiences to those attitudes, feelings, and avoidances.

Prediction: when intimate childhood association exists (whether or not between relatives), these aversive attitudes, feelings, and behaviors exist. Putatively supported by the rarity of sibling incest, given standard child-rearing practices, as well as the Israeli kibbutzim data (collected by Melford Spiro 1958, Yonina Talmon 1964, and Joseph Shepher 1971, 1983), and by sim-pua practices in Taiwan (that Arthur Wolf has published extensively on), which provide evidence for the mechanism being familiarity or attachment-based. Counter-evidence: finding individuals who were intimate childhood associates who have erotic feelings for one another, engaged in sexual behavior, later in life.
Retrodiction: when these aversive attitudes, feelings, and behaviors are missing, you will also find an absence of intimate childhood association. Putatively supported by cases of consensual sibling sexual attraction and incest when reunited following childhood separation, i.e., ARMGSA. Counter-evidence: finding individuals who have erotic feelings for one another, engaged in sexual behavior, later in life but also were intimate childhood associates.

One measure of the strength of the putative effect, so characterized, would be how tight this cluster is; another would be the % of individuals who prove exceptions to it, set against the % in some comparable group.

We might also wonder whether the converse of a version of this formulation of the Westermarck Effect also captures part of what Westermarck or neo-Westermarckians have in mind when they appeal to evidence for the effect:

if two sexually mature siblings have a psychological aversion to sexual relations to one another, lack erotic feelings for one another, and as a result, avoid incestual behaviors, then those individuals were intimate childhood associates, having been raised together for a number of years from early in life.

Here intimate childhood association is presented as a necessary condition for aversive attitudes, feelings, and behaviors later in life between relatives. It can also be read as making both predictions and retrodictions about what one finds if one traces individual life histories.

Prediction: siblings who lack intimate childhood association will also lack the aversive attitudes, feelings, and behaviors later in life. Putatively supported by cases of consensual sibling incest when reunited following childhood separation, i.e., ARMGSA. Counter-evidence: finding sibs without intimate childhood association but who have the aversive attitudes, feelings, and behaviors later in life.
Retrodiction: siblings who have these aversive attitudes were also intimate childhood associates. Putatively supported by the rarity of sibling incest, given standard child-rearing practices. Counter-evidence: finding sibs with aversive attitudes, feelings, behaviors, but who were not intimate childhood associates.

Again, the same kinds of measures of the strength of the effect can be offered as in the previous case.

Why does ARMGSA offer support for the claim that childhood association is both a necessary and a sufficient condition for sexual aversion between siblings? Sufficiency is easy: it’s an unexpected finding made possible by recent adoption practices and norms governing the release of information about genetic parents. But the claim that childhood association is necessary for aversion implies something like this: that unless siblings undergo intimate childhood association, they will experience GSA as adults. And that is so despite the social taboos that exist against the behaviors those feelings can lead to. This suggests that there are other mechanisms that make one sibling especially sexually attractive to another that are inhibited by childhood association. The reason to take this stronger claim serious is the phenomenology that people experiencing ARMGSA report: it feels compulsive or obsessional for people who are not, in generally, dispositionally like that. If it turns out that this experience occurs amongst those who are otherwise very diverse in their profiles, and that one never or rarely finds that phenomenology amongst siblings raised together, then we have a reason to accept the stronger claim about the relationship between childhood association amongst siblings and the absence of sexual aversion.

Finally for now, how should we spell out that pesky “intimate childhood associates”? One suggestion is a variant on the aphorism familiarity breeds contempt: familiarity breeds indifference or perhaps familiarity breeds aversion, where it is only familiarity during childhood that matters. Another is an attachment hypothesis: that what matters about intimate childhood association is during it, siblings become emotionally attached to each other in a way that precludes later sexual attraction. If that were the case, then there could be other ways of gaining that emotional attachment that has the same effect, e.g., through the provision or reception of offspring care. Whether it is familiarity or attachment or something else, a further story needs to be told about why that should lead to an inhibition on sexual attraction later in life.

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