Causation in the Nature-Nurture Debate: The Case of Genotype-Environment Interaction by James Gregory Tabery Bachelor of Science, Fairfield University, 2000 Submitted to the Graduate Faculty of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2007 UNIVERSITY OF PITTSBURGH COLLEGE OF ARTS AND SCIENCES This dissertation was presented by James Gregory Tabery It was defended on July 17, 2007 and approved by Robert C. Olby, Research Professor, Dept. of History and Philosophy of Science Michael Pogue-Geile, Associate Professor, Psychology Department Kenneth F. Schaffner, University Professor, Dept. of History and Philosophy of Science Dissertation Director: Sandra D. Mitchell, Professor, Dept. of History and Philosophy of Science Dissertation Director: Paul E. Griffiths, Professor, Philosophy, University of Queensland ii Copyright © by James Gregory Tabery 2007 iii Causation in the Nature-Nurture Debate: The Case of Genotype-Environment Interaction James Gregory Tabery University of Pittsburgh, 2007 I attempt to resolve an aspect of the nature-nurture debate. Consider a typical nature-nurture question: Why do some individuals develop a complex trait such as depression, while others do not? This question incorporates an etiological query about the causal mechanisms responsible for the individual development of depression; it also incorporates an etiological query about the causes of variation responsible for individual differences in the occurrence of depression. Scientists in the developmental research tradition of biology investigate the former; scientists in the biometric research tradition of biology investigate the latter. So what is the relationship? The developmental and biometric research traditions, I argue, are united in their joint effort to elucidate what I call difference mechanisms. Difference mechanisms are regular causal mechanisms made up of difference-making variables that take different values in the natural world. On this model, individual differences are the effect of difference-makers in development that take different values in the natural world. I apply this model to the case of genotype-environment interaction (or G×E), showing that there have actually been two separate concepts of G×E: a biometric concept (or G×EB) and a developmental concept (or G×ED). These concepts also may be integrated via the difference mechanisms model: G×E results from the interdependence of difference-makers in development that take different values in the natural world. iv TABLE OF CONTENTS ACKNOWLEDGMENTS………………………………………………………………………...x PREFACE………………………………………………………………………………………..xii 1. Introduction……………………………………………………………………………………..1 1.1. Genotype-Environment Interaction…………………………………………………..2 1.2. Genotype-Environment Interaction in the Nature-Nurture Debate…………………..7 1.3. G×EB vs. G×ED……………………………………………………………………….9 1.4. Difference Mechanisms and the Interdependence of Difference-Makers in Development that Take Different Values in the Natural World…………………….11 2. R. A. Fisher, Lancelot Hogben, and the Origin(s) of Genotype-Environment Interaction……14 2.1. Introduction………………………………………………………………………….14 2.2. R. A. Fisher and the “Nonlinear Interaction of Heredity and Environment”……….16 2.2.1. The Environment Expunged………………………………………………17 2.2.2. Rothamsted and the Environment Reconsidered—the Origin of G×EB…..21 2.3. Lancelot Hogben and the “Interdependence of Nature and Nurture”……………….28 2.3.1. Cleaning the Augean Stables……………………………………………...35 2.3.2. The William Withering Memorial Lectures………………………………39 2.3.3. From Development to Interaction—the Origin of G×ED………………….47 2.4. Fisher vs. Hogben: On the Importance of Genotype-Environment Interaction……..54 2.5. The Legacies of Fisher and Hogben: G×EB vs. G×ED………………………………61 2.6. Conclusion…………………………………………………………………………..64 3. Genotype-Environment Interaction in the IQ Controversy…………………………………...66 3.1. Introduction………………………………………………………………………….66 3.2. Genotype-Environment Interaction in the IQ Controversy…………………………71 3.2.1. The Argument from Genotype-Environment Interaction…………………76 3.2.2. The Argument from Genotype-Environment Interaction Dismissed……...93 3.3. Science Studies on Genotype-Environment Interaction in the IQ Controversy…….96 3.4. G×EB vs. G×ED…………………………………………………………………….101 3.5. Conclusion…………………………………………………………………………110 4. Difference Mechanisms……………………………………………………………………...112 4.1. Introduction………………………………………………………………………...112 4.2. The Case of Genotype-Environment Interaction…………………………………..119 4.2.1. The Call for an Isolationist Pluralism……………………………………121 4.2.2. The Call for an Integrative Pluralism…………………………………….127 4.3. Difference Mechanisms……………………………………………………………130 4.3.1. Causes as Difference-Makers……………………………………………131 4.3.2. Difference-Makers in Development that Take Different Values in the Natural World……………………………………………………………133 4.3.3. The Interdependence of Difference-Makers in Development that Take Different Values in the Natural World…………………………………..143 4.4. Conclusion…………………………………………………………………………147 5. Rats! So What Is G×E? ……………………………………………………………………...149 5.1. Introduction………………………………………………………………………...149 5.2. G×EB vs. G×ED…………………………………………………………………….151 v 5.2.1. G×EB……………………………………………………………………..151 5.2.2. G×ED……………………………………………………………………..155 5.3. G×EB and G×ED……………………………………………………………………158 5.3.1. What Is an Analysis of Variance?………………………………………..158 5.3.1.1. Mill’s Methods…………………………………………………159 5.3.1.2. Fisher’s Methods……………………………………………….161 5.3.2. What Is the Measure Measuring?………………………………………..168 5.4. Conclusion…………………………………………………………………………173 6. Conclusion…………………………………………………………………………………...175 6.1. Causes of Controversy……………………………………………………………..175 6.2. Making a Difference with Difference Mechanisms………………………………..177 BIBLIOGRAPHY………………………………………………………………………………179 vi LIST OF TABLES Table 1: The components of the biometric and developmental research traditions………………2 Table 2: The components of the biometric research tradition…………………………………...28 Table 3: The components of the developmental research tradition……………………………...54 Table 4: The components of the biometric and developmental research traditions……………..59 Table 5: The components of the biometric research tradition………………………………….105 Table 6: The components of the developmental research tradition…………………………….108 Table 7: The components of the biometric and developmental research traditions……………109 Table 8: The components of the biometric and developmental research traditions……………117 Table 9: The components of the biometric research tradition………………………………….153 Table 10: The components of the developmental research tradition…………………………...156 Table 11: Subgroup means for hypothetical rat population…………………………………….164 Table 12: Subgroup means for actual rat population. Data from Cooper and Zubek (1958)…..167 vii LIST OF FIGURES Figure 1: Norms of reaction for genotypes conferring low and high MAOA activity in response to varying levels of childhood maltreatment………………………………………............4 Figure 2: R. A. Fisher……………………………………………………………………………17 Figure 3: Fisher’s experimental design for differential response of potato varieties to manurial treatments………………………………………………………………………………...24 Figure 4: Fisher’s analysis of variation due to manuring, variety, deviations from summation formula, and variation between parallel plots……………………………………………25 Figure 5: Lancelot Thomas Hogben……………………………………………………………..29 Figure 6: Two frogs, 19 days after pituitary operation by Hogben. (A) partial removal of only anterior lobe. (B) complete removal……………………………………………………...32 Figure 7: Hogben’s norms of reaction for low-bar and ultra-bar Drosophila strains derived from Krafka (1920)…………………………………………………………………………….45 Figure 8: Krafka’s norms of reaction for unselected bar stock (top), low-bar stock (middle), and ultra-bar stock (bottom) eye-facets in response to temperature………………………….52 Figure 9: Lewontin’s hypothetical reaction norm graphs for phenotypic traits caused by canalization……………………………………………….................................................79 Figure 10: Lewontin’s hypothetical reaction norm graphs for phenotypic traits caused by an additive genotype-environment relation………………………………………………….80 Figure 11: Lewontin and Feldman’s hypothetical reaction norm graph…………………………81 Figure 12: Lewontin’s actual reaction norms for viability of fourth chromosome homozygotes of Drosophila pseudoobscura……………………………………………………………….84 Figure 13: Photograph of Richard Lewontin from 1973 Boston Phoenix article “The Brains Do Battle in I.Q. Controversy”……………………………………………………………….87 Figure 14: Layzer’s hypothetical reaction norm graph for three genotypes (x1, x2, and x3) exposed to a variable environment (y)…………………………………………………...91 Figure 15: Molecular, cellular, brain-system, and organismal mechanisms involved in the production of spatial memory in rats……………………………………………………114 Figure 16: Sample Hebb-Williams maze test configurations…………………………………..115 Figure 17: Reaction norm graphs for s/s, s/l, and l/l groups measured for probability of a major depression episode (y-axis) across an array of environments (x-axis). (A) Hypothetically parallel reaction norms. (B) Non-parallel reaction norms from empirical data (Caspi et al. 2003)…………………………………………………………………………………….121 Figure 18: Mechanisms involved in the production of depression. (A) Protein synthesis at the molecular level. (B) Synapse transmission at the cellular level (modified from Hariri and Holmes 2006, Figure 1). (C) Amygdala-cingulate feedback at the brain-system