The genetics of morality and prosociality Salomon Israel, Liat Hasenfratz and Ariel Knafo-Noam Genetically informed research of phenotypes related to morality has proliferated rapidly in the last few years, sparking paradigm shifts from theories based solely on socialization toward ones integrating biological influences. Here, we review recent genetic research in the area of morality that has received the most attention in genetic studies: prosociality — positive emotions, attitudes, and behaviors directed toward others. Individual differences in prosociality emerge early in life, increase in heritability as children develop, and are related to variation in genes regulating neurotransmitter systems central to social affect, cognition, and behavior. The majority of molecular genetic studies have been candidate-based, however genome-wide studies are emerging, with the potential to elucidate novel biological pathways associated with individual differences in morality. Address Department of Psychology, The Hebrew University of Jerusalem, Jerusalem, Israel Corresponding authors: Israel, Salomon (salomon.israel@mail.huji.ac.il) and Knafo-Noam, Ariel (ariel.knafo@huji.ac.il) Current Opinion in Psychology 2015, 6:55–59 This review comes from a themed issue on Morality and ethics Edited by Francesca Gino and Shaul Shalvi http://dx.doi.org/10.1016/j.copsyc.2015.03.027 2352-250X/# 2015 Published by Elsevier Ltd. Introduction People vary markedly in what they appraise to be right from wrong; in how they experience or report emotions that motivate moral action; in the extent to which these moral intentions override self-oriented preferences; and in the degree by which they behave consistently with their morals. Understanding the causes behind this heterogene- ity in moral sentiment and behavior continues to be a topic of profound interest across the social sciences. Genetically informed research of phenotypes related to morality has proliferated rapidly in the last few years in psychology, economics, and political science, sparking paradigm shifts from theories focused on socialization toward ones inte- grating biological influences [1,2  ]. The phenotype that has received by far the most attention in genetic research on morality is prosociality — positive emotions, attitudes, and behaviors directed toward others. Prosociality is a compelling model phenotype because it shares phyloge- netic origins with other primates and, in humans, it is amenable to measurement in both children and adults [3]. Measurement of genetic factors contributing to prosociality Like morality, measurement of prosociality is multidimen- sional, spanning affect, cognition, attitude, and behavior [4  ]. At the affective level, prosociality includes empa- thy — an other-oriented affective tendency to compre- hend and share the emotional states of others [5  ]. At the cognitive level, aspects of Theory of Mind — the ability to appreciate others’ mental states and to under- stand that others have beliefs, intentions, and perspectives that are different from one’s own — may be necessary for some prosocial behaviors [6]. At the attitudinal level are values such as benevolence — regard toward the welfare of close contacts, and universalism — regard for the welfare of all people and for nature [7]. Finally, at the behavioral level is prosocial-behavior — voluntary behavior intended to benefit another [5  ]. Fitting the multidimensionality of this construct, multiple modes of measurement (self-report and informant-report, experimental decision making tasks, brain imaging) are regularly employed to observe how genetic effects relate to individual differences in prosoci- ality. The bulk of this research has relied on quantitative- genetic methods, however rapid advancements in the feasibility of genotyping has spurred findings based on molecular genetic techniques. The integrative picture emerging from these research programs is one of indi- vidual differences in prosociality emerging early in life, increasing in heritability as children develop, and related to variations in genes regulating neurotransmitter sys- tems central to social affect, cognition, and behavior [3]. Research examining the synergistic processes by which genes and the environment together influence prosoci- ality is also underway. Most quantitative research partitioning the variance for morality phenotypes into genetic and environmental fac- tors has traditionally relied on the twin design. In this design, the covariance between scores for a given phe- notype is compared between identical (monozygotic) twins — who share virtually all of their genetic se- quence — and fraternal (dizygotic) twins — who share, on average, half of their genetic variance. Assuming that MZ and DZ twins are equal in terms of how similar their environments are, then greater MZ twin concordance indicates a genetic basis for the measured phenotype (heritability). Similarity beyond this genetic effect is attributed to environmental influences making siblings similar (shared environment effect), and any differences Available online at www.sciencedirect.com ScienceDirect www.sciencedirect.com Current Opinion in Psychology 2015, 6:55–59