Why Behavioral Genetics Matters
Behavioral genetics has occupied a unique position within psychology, repeatedly inciting acrimonious debates over many of the discipline's defining issues. In their article published in this issue of Perspectives on Psychological Science, Plomin, DeFries, Knopik, and Neiderhiser (2016) push the academic controversies to the side and show how behavioral genetic research has fundamentally altered our understanding of the nature of individual differences in psychological traits. They are to be commended for their comprehensive summary of enduring results. Indeed, in the midst of the ongoing "replicability crisis," their review can be read as a celebration of the field's maturity and accomplishments. Plomin, DeFries, Knopik, and Neiderhiser (PDKN) organize their review around 10 robustly replicated "big" findings. Those whose view of behavioral genetics is anchored in the nature nurture debates of the 20th Century will be surprised by the broad scope of the topics covered. PDKN describe how behavioral genetic research has enriched our understanding of psychological development and even the nosology of mental illness. Significantly, four of their findings have very little to do with genetics at all, being specifically concerned with the nature of environmental influence. Elsewhere, these authors have made the point that some of the strongest evidence for the existence of environmental influences derives from behavioral genetic research, and for good reason. Furthermore, they justly emphasize that strong causal interpretations of behavioral genetic findings are indeed warranted. Because drawing causal inferences from observational data can be so often fraught with difficulty, one of the attractions of behavioral genetics for the larger field of psychology is that it offers a set of complementary research designs justifying strong inference in observational settings (Lee, 2012; McGue, Osler, Christensen, 2010) But is behavioral genetics really less susceptible to falsepositive findings than other areas of psychology? PDKN believe so, and they provide five reasons to justify that belief. Ironically, the first of these, which they designate "Controversy," owes as much to the critics of the field as to behavioral geneticists themselves. Over the past 50 years, psychology has viewed behavioral genetics with a fair degree of skepticism. The doubts of their colleagues have forced behavioral geneticists to adopt high standards of proof large sample sizes, converging evidence from complementary research designs, transparent multisite collaborations, and attention to alternative explanations. Making common cause with their colleagues in human genetics studying diseases and anthropometric traits, behavioral geneticists at the molecular frontier have mustered the will to stamp out nonreplicability, and the resulting culture has turned the broad endeavor of gene trait mapping into one of the most trustworthy fields in all of biomedical and social science (Ioannidis, 2013) Seeing that uncritical acceptance of research findings has proven a major impediment to scientific progress elsewhere (Duarte et al. 2015) behavioral geneticists may perhaps owe a debt to those who have challenged their methods and interpretations. The benefits of being "blessed by brilliant enemies," as E. O. Wilson put it, can be appreciated by virtue of their absence from an area of behavioral genetic research that did not make PDKN's list: gene environment interaction (GxE) There is general recognition that GxE effects on behavior are pervasive. The downside of this recognition, in our view, is that reports of GxE are not met with the same skepticism as findings from other areas of behavioral genetics. Over the past 15 years, there has been a consequent explosion of published GxE research in psychology. Unfortunately, much of this research has been susceptible to the same limitations with which other areas of psychology are struggling small samples, ad hoc analytical decisions, multiple model tests, etc. And the result? GxE research has a rather poor record of replicability, leading to calls for its claims to meet the same standards of proof that have been established in other areas of genetics (Duncan Keller, 2011) The only place where we might quibble with PDKN's conclusions is their analysis of the search for marginal 611932 PPSXXX10.1177/1745691615611932Lee, McGueWhy Behavioral Genetics Matters research article2015
Perspectives on psychological science a journal of the Association for Psychological Science