Behavioural genetics and the anti-conceptual mentality

A behavioural geneticist called Robert Plomin has written a book called “Blueprint: How DNA Makes Us Who We Are”, which will be coming out soon. I haven’t read it and I don’t expect I will read it. Human behavioural genetics is bunk. I will explain why it is bunk and say something about why so many people apparently think it is plausible.

Behavioural geneticists like to claim that human behaviour is influenced by genes and by something called “environment”. They claim to be able to tell the influence of genes apart from the influence of environment by clever experiments. For example, identical twins have more genes in common than fraternal twins, who have more genes in common  than unrelated people. So if we look at the behaviour of identical twins compared to fraternal twins and the identical twins are more similar then their behaviour may be more genetically influenced. There are variations on these experiments that involve twins being reared apart and that sort of thing. See Chapter 6 of “Behavioral Genetics”, Sixth Edition by R. C. Plomin, J. C. DeFries, V. S. Knopik and J. M. Neiderhiser. On p.81, the authors write:

If a trait is influenced genetically, identical twins must be more similar than fra­ternal twins. However, it is also possible that the greater similarity of MZ twins is caused environmentally rather than genetically because MZ twins are the same sex and age and they look alike. The equal environments assumption of the twin method assumes that environmentally caused similarity is roughly the same for both types of twins reared in the same family. If the assumption were violated because identi­cal twins experience more similar environments than fraternal twins, this violation would inflate estimates of genetic influence. The equal environments assumption has been tested in several ways and appears reasonable for most traits (Bouchard & Prop­ ping, 1993; Derks, Dolan, & Boomsma, 2006).

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A subtle, but important, issue is that identical twins might have more similar experiences than fraternal twins because identical twins are more similar genetically. That is, some experiences may be driven genetically. Such differences between iden­tical and fraternal twins in experience are not a violation of the equal environments assumption because the differences are not caused environmentally (Eaves, Foley, & Silberg, 2003).

They continue to describe studies in which twins were adopted:

The adoption-twin combination involves twins adopted apart and compares them with twins reared together. Two major studies of this type have been conducted, one in Minnesota (Bouchard, Lykken, McGue, Segal, & Tellegen, 1990; Lykken, 2006) and one in Sweden (Kato & Pedersen, 2005; Pedersen, McClearn, Plomin, & Nes- selroade, 1992). These studies have found, for example, that identical twins reared apart from early in life are almost as similar in terms of general cognitive ability as are identical twins reared together, an outcome suggesting strong genetic influence and little environmental influence caused by growing up together in the same family (shared family environmental influence).

Let’s see what they say about tests of the EEA in Derks, Dolan, & Boomsma, 2006:

It has been shown that MZ twins in childhood more often share playmates, share the same room, and dress more alike than same-sex DZ twins (Loehlin & Nichols, 1976). However, this does not necessarily imply that the EEA is violated. First, the greater environmental similarity in MZ than DZ twins does not have to be related to a greater phenotypic similarity. Second, even if a greater environmental similarity is related to a greater phenotypic similarity, this association could be mediated by a greater genetic similarity in MZ than DZ twins (Scarr & Carter-Saltzman, 1979). The EEA is only violated when the correlation between environmental similarity and trait similarity is significantly greater than zero within zygosity groups. Eaves et al. (2003) concluded on the basis of simulation studies that the absence of any association between environmental similarity and trait similarity justifies the claim that environmental similarity is not a factor in twin resemblance. However, the counterclaim that the presence of an association between environmental similarity and trait similarity falsifies the EEA is unfounded.

So the sort of thing that behavioural geneticists have in mind when they discuss the “same environment” is whether they are in the same room and have the same playmates. If the twins are adopted they don’t live in the same room or have the same playmates so they don’t have the same environment.

This line of argument doesn’t work. A person can consider what choice to make in the light of the ideas he has adopted. So all that has to happen for separated children to have a similar “environment” is that the ideas they adopt have something to say about how you should behave based on your appearance or on anything else that can be affected by genetics like eyesight. If you have poor eyesight you may end up wearing glasses, and this may result in you being treated as the kind of person who wears glasses: you may be treated like a geek or whatever. So the relevant similarities in environment are mostly not on the level of concretes like being in the same room. Nor is there any way that intellectual similarities in environment could be removed or accounted for.

Ayn Rand had something to say about the sort of blindness to ideas exhibited above: they have the anti-conceptual mentality. In Philosophy: Who Needs It, Chapter 4, Rand writes:

These cases are examples of the anti-conceptual mentality. The main characteristic of this mentality is a special kind of passivity: not passivity as such and not across-the-board, but passivity beyond a certain limit—i.e., passivity in regard to the process of conceptualization and, therefore, in regard to fundamental principles. It is a mentality which decided, at a certain point of development, that it knows enough and does not care to look further. What does it accept as “enough”? The immediately given, directly perceivable concretes of its background—“the empiric element in experience.”

To grasp and deal with such concretes, a human being needs a certain degree of conceptual development, a process which the brain of an animal cannot perform. But after the initial feat of learning to speak, a child can counterfeit this process, by memorization and imitation. The anti-conceptual mentality stops on this level of development—on the first levels of abstractions, which identify perceptual material consisting predominantly of physical objects—and does not choose to take the next, crucial, fully volitional step: the higher levels of abstraction from abstractions, which cannot be learned by imitation.

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The anti-conceptual mentality takes most things as irreducible primaries and regards them as “self-evident.” It treats concepts as if they were (memorized) percepts; it treats abstractions as if they were perceptual concretes. To such a mentality, everything is the given: the passage of time, the four seasons, the institution of marriage, the weather, the breeding of children, a flood, a fire, an earthquake, a revolution, a book are phenomena of the same order. The distinction between the metaphysical and the man-made is not merely unknown to this mentality, it is incommunicable.

To the behavioural geneticist, people don’t have ideas. Anything that isn’t a gene has to be something concrete like a room or a particular playmate. Ideas and choices don’t exist or they are irrelevant.

An article covering Plomin’s new book contains the following paragraph:

He [Plomin] finds that genetic heritability accounts for 50% of the psychological differences between us, from personality to mental abilities. But that leaves 50% that should be accounted for by the environment. However, Plomin argues, research shows that most of that 50% is not attributable to the type of environmental influences that can be planned for or readily affected – ie it’s made up of unpredictable events. And of the environmental influences that can be moderated, much of it, he argues, is really an expression of genetics.

The position attributed to Plomin here doesn’t acknowledge the possibility of being able to think rationally about some event you haven’t predicted and solve any problem it presents. Concepts and explanations don’t exist in this worldview. If, like me, you get a sinking feeling of boredom when you read stuff written by Plomin and other human behavioural geneticists, now you know why – they have no ideas of any substance. They have nothing useful or interesting to say about anything.