Genetics as an Omitted Variable in Psychology and Social Science

Here’s the abstract of an article by Frank Schmidt in the Archives of Scientific Psychology:

Governments often base social intervention programs on studies done by psychologists and other social scientists.Often these studies fail to mention other research suggesting that such interventions may have a limited chance of actually working. The omitted research that is not mentioned often shows that the behaviors and performances targeted for improvement by the environmental intervention programs are mostly caused by genetic differences between people and for that reason may be more difficult to change than implied in these studies. This is particularly true when the goal is to greatly reduce or eliminate differences between people in such domains as school achievement, impulsive behaviors, or intelligence. This problem of omitted research creates two problems. It tends to call into question the credibility of all social science research, even the studies that do not omit relevant research.And from an applied point of view, it leads to the expenditure of taxpayer dollars on programs that are unlikely to produce the desired outcomes.

Here are a few paragraphs from early in the article:

The first area of problem research focuses on the ostensible effects of life experiences on life outcomes. This broad area includes many research areas and topics in different psychological specialties. The aspect of much of this research that is problematic is the common failure to acknowledge the relevant findings in the field of behavior genetics.

These findings show that virtually all tendencies, traits, behaviors, and life outcomes have a substantial genetic basis (cf.Bouchard, 1997a, 1997b, 2004; Colarelli & Arvey, 2015; Lee & McGue, 2016; McGue & Bouchard, 1998; Plomin, DeFries, Knopik,& Neiderhiser, 2013; Plomin, DeFries, Knopik, & Neiderhaise, 2016; Plomin, Owen, & McGuffin, 1994; Turkheimer, 2000). Even day-to-day variability in positive and negative affect has been shown to be substantially heritable (Zheng, Plomin, & von Stumm, 2016).Research has further shown that most supposedly purely environmental variables (such as the number of books and magazines in the home) that are often concluded to be environmental causes of later life outcomes are themselves genetically influenced (e.g., see Plomin & Bergman, 1991; Plomin et al., 2016). That is, they are substantially influenced by the genetic makeup of the parents in the home, whose genes are passed on to their offspring.

Research also indicates that people seek out and create their own environments based on their genetically influenced proclivities and interests (Scarr, 1996; Scarr,1989; Scarr & McCartney, 1983).The forgoing is a very brief overview but is believed to be sufficient to establish the main point. These behavior genetics findings do not mean that experiences of people do not have any effect on their later life outcomes. But they do mean that failure to even mention potential or likely genetic influences on these outcomes is a serious problem, one that reduces the credibility of the research. The following are some examples of studies that fail to acknowledge these well-established research findings.

A number of studies report that children who grow up in dysfunctional or abusive families tend later as adults to be abusive themselves(cf. Kaufman & Zigler, 1987, 1989). The interpretation is typically entirely environmental: It is assumed that the earlier experiences cause the later behavior. There is no acknowledgment of the fact that all major behaviors, including abusive personality tendencies, have a genetic component (Plomin, Owen, & McGuffin, 1994; Plomin et al.,2016; Turkheimer, 2000). There is no mention of the possibility that the genes that lead the parents to be abusive are passed on to their children and are an important reason why their children later themselves also become abusive as adults (Rowe, 1994). There are numerous examples of such studies in the literature (Kaufman &  Zigler,1987, 1989)

Here’s the final paragraph:

The hope is that the information presented in this article will lead to recognition in the literature of the role of behavior genetics findings in studies interpreting relationships between experiences and later life outcomes; and to recognition of the central role of GMA in studies examining specific aptitudes and abilities. At present the literatures in these two areas contain many studies that are scientifically incomplete. These changes are important for establishment of the credibility of research conclusions in these areas and may help to deter credibility losses across other areas of research.

I note that this also has implications for economic theory…