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Smart People / Cognitive Enhancement
Published in Jonathan Anomaly, Creating Future People, 2020
Behavior genetics was born when Francis Galton began studying twins separated at birth in order to sort out the effects of nature and nurture on personality (1875). The methods for measuring traits have improved considerably, and the number of twins studied throughout their life course is now in the tens of thousands. The first rigorous studies began in the 1970s, and we now have five decades of research, including thousands of papers published in peer-reviewed journals (Plomin, 2018). Intelligence is among the most carefully studied traits in psychology. Behavior genetics researchers have also studied many other traits, ranging from health and height to political ideology and religiosity, in order to figure out how heritable they are.
Genetic Principles
Published in Gail S. Anderson, Biological Influences on Criminal Behavior, 2019
Heritability is a term that is commonly used in behavior genetics studies. It is a measure of the proportion of the variance or variability in a trait that can be attributed to genetics, as opposed to the variance attributed to the environment.7 It is usually presented as a percentage or on a scale of 0–1 (heritability coefficient). For example, a heritability of 60%, or 0.6, suggests that 60% of the variability for that trait in a population is under genetic control. This can be somewhat misleading, as usually, a large number of genes are involved, each contributing a differing amount of genetic control to the trait. Some may only have a very tiny contribution, and others much more, but the heritability statistic does not distinguish this. Moreover, in many cases, there is an interactive effect between the genes and the environment.
The Epidemiological Approach
Published in Hanna Pickard, Serge H. Ahmed, The Routledge Handbook of Philosophy and Science of Addiction, 2019
One of the most attractive features of epidemiological case-crossover research is the use of the subject as his/her own control. This approach finesses a question that always bedevils behavioral genetics research on MZ co-twins, when the goal is to identify environmental determinants of disease outcomes. In these MZ co-twin studies, relative risk estimation is based on the number of twin pairs with an exposed case and with an non-exposed co-twin control (E+, E- discordance), divided by the number of twin pairs with an exposed co-twin control and a non-exposed case (E-, E+ discordance). The ‘fly in the ointment’ unanswered question in these between-individual studies is this: “Why did one twin get exposed when the other MZ co-twin did not get exposed, even though both twins shared genetic vulnerability traits and many facets of environment up to the time of the study?” The epidemiological case-crossover approach, with its within-individual approach, also matches for all genes (by virtue of a ‘subject as own control’ design), and in addition it matches for all environmental experiences (and for gene-by-environment interactions), up to the time of the study interval. In this sense, more than is true in behavior genetics research on MZ co-twins, the result of case-crossover research is enhanced control of genetic, epigenetic, and early-life determinants of the case outcome, as well as many gene–environment interactions. Self-matching in case-crossover research motivates conditional contingency tables, as illustrated in Table 21.1, or logistic GZLM for RR estimation.
Commentary on “Same-Sex Marriage and Common Mental Health Diagnoses: A Sibling Comparison and Adoption Approach”
Published in The Journal of Sex Research, 2023
The current study was not designed to find direct linkage between genes related to sexual orientation, mental illness, or their overlap. Instead, it was focused on whether common familial factors might explain part of the association between sexual orientation and mental health diagnoses. Given the long history of associating homosexuality with mental illness, articles such as this receive both praise and criticism. Part of the resistance to talking about findings from behavior genetics research, especially as it relates to stigmatized minorities, is related to fears of (re)pathologization, (re)criminalization, and the potential use as justification for “corrective” or “eugenic” interventions. On the other hand, modern behavior genetics strives to increase understanding of the interplay of genes and environment. We are always and at all times the product of our biology in interaction with our environment. Every thought we have is a neuro-chemical reaction. Dismissing the study of potential biological influence on human behavioral trait development because it might be potentially socially dangerous if misapplied, runs the risk of ignoring the potential insights that an integrated bio-psycho-social perspective might afford. Indeed, the Xu et al. study serves to underscore how research on behavioral genetics can point to the need to search for additional unmeasured factors that may help explain the mental health disparities associated with sexual orientation.
Environmental Sensitivity in Adults: Psychometric Properties of the Japanese Version of the Highly Sensitive Person Scale 10-Item Version
Published in Journal of Personality Assessment, 2023
Shuhei Iimura, Kosuke Yano, Yukiko Ishii
As has been suggested by influential developmental theories such as the bioecological model of human development (Bronfenbrenner & Morris, 2006), from birth to death, humans are affected by a wide range of environmental influences, and we undergo neurophysiological and psychosocial development through dynamic interactions with these environments. In this sense, humans are social beings that cannot be separated from their environment. However, it is important to note that individual differences in sensitivity to environmental influences can be observed (e.g., Aron et al., 2012; Belsky & Pluess, 2009; Boyce & Ellis, 2005; Ellis et al., 2011; Monroe & Simons, 1991; Pluess & Belsky, 2013). Some individuals are more likely to be susceptible to both positive and negative experiences than others. Currently, such individual differences in sensitivity to the environment are being empirically studied from the perspectives of developmental psychology, neurophysiology, behavioral genetics, molecular genetics, and personality psychology within the integrated framework of Environmental Sensitivity Theory (Greven et al., 2019; Pluess, 2015). In this paper, we discuss our development of a brief Japanese version of the Highly Sensitive Person (HSP) scale to measure individual differences in sensitivity in adults (Aron & Aron, 1997; Takahashi, 2016), and provide new information on its psychometric properties.
Perceived Stress and Sleep Quality in Midlife and Later: Controlling for Genetic and Environmental Influences
Published in Behavioral Sleep Medicine, 2020
Yueqin Hu, Marieke Visser, Sierra Kaiser
In addition to these hypotheses, given the possible heritability of perceived stress and sleep quality, we will also analyze the influence of additive genetics, shared environment and individual-specific environment in the stress–sleep relationship. Behavior genetics by means of twin, family and adoption studies can help decipher the relative contribution of genetic and environmental variability in behavioral traits (Moore et al., 2011). This study will employ the methods of behavior genetics, and use the ACE model (Boomsma, Busjahn, & Peltonen, 2002; Falconer, 1960; Neale & Cardon, 1992) on monozygotic twins and dizygotic twins to separate the contribution of genes, shared environment, and individual-specific environment. Then, for variables that are largely influenced by genes and shared environment, we will use the co-twin design (CTC, e.g, Burt et al., 2010; McGue, Osler, & Christensen, 2010) to control for any genetic and familial confounds.