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The Nature and Nurture of Generosity What can we learn from behavioral g enetics ?

This seminar explores the relationship between genetics, education, and prosocial behavior, specifically generosity. By examining twin studies and biometric modeling, we can gain a better understanding of the underlying factors that contribute to individual differences in generosity.

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The Nature and Nurture of Generosity What can we learn from behavioral g enetics ?

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  1. The Nature and Nurture of GenerosityWhatcan we learnfrombehavioralgenetics? René Bekkers Center for Philanthropic Studies VU University Amsterdam Evolutionary and SocialPsychology Seminar December 19, 2016

  2. Thanks • To the McArthur Foundation for funding the MIDUS data collection. • Colleagues who gave feedback: Dorret Boomsma, Dinand Webbink, Sara Konrath, Paul van Lange, Daniëlle Posthuma. EVSOP

  3. EVSOP

  4. Three questions • How alike are twins in the United States with respect to prosocial behavior? • Are differences among twins in giving and volunteering related to differences in education and religion? • If so, what explains these relationships? EVSOP

  5. EVSOP

  6. EVSOP

  7. Number of publicationsper yearaboutphilanthropybyacademic discipline (1899-2009) Source: Bekkers & Dursun (2013), based on Bekkers & Wiepking (2011). ‘A Literature Review of Empirical Studies of Philanthropy: Eight Mechanisms that Drive Charitable Giving’. Nonprofit and Voluntary Sector Quarterly, 40(5): 924-973. Available at www.understandingphilanthropy.com EVSOP

  8. Ubiquitouscorrelates of philanthropy • Religion: • Affiliation (yes>no) • Denomination (Protestant>Catholic) • Participation (churchattendance) • Education: • Level achieved The variancebetweenfields of study is small EVSOP

  9. Where do the correlationsoriginate? The more general research questions: • Why are religion and educationcorrelatedwith prosocial behavior? • To whatextent are these relationships the result of environmentalinfluences? • Are these relationshipscausal? EVSOP

  10. Selection and causation EVSOP

  11. All selection, no causation EVSOP

  12. Selection and Causation About 60%? IQ, parentalincome, socialscience classes, college plans, extraversion, opennesstoexperience Bekkers, R. & Ruiter, S. (2008). ‘Education and voluntary association participation: Evidence for selection and causation’. Paper presented at the 103d ASA Annual Meeting, Boston, August 2, 2008. EVSOP

  13. Selection, causation, mediation EVSOP

  14. EVSOP

  15. Three ‘theories’ onphilanthropy Philanthropy variesbetweensocialgroups • because the resources of groupmembersvary; • because the socialvalues of groupsvary; • becausemembers of different groups have different self-identities. EVSOP

  16. EVSOP

  17. The ideal experiment wouldrandomizeeducation VWO = highersecondaryeducation (≤ gymnasium) VMBO = lowervocationaleducation EVSOP

  18. Monozygotictwins EVSOP

  19. The uniqueenvironmentalinfluence of education Note that shared environmental influences are also excluded by design in this analysis EVSOP

  20. Whatbehavioralgeneticists do: the ACE model EVSOP

  21. Note • The first law of behavior genetics, as formulated by Eric Turkheimer (2000): “All human behavioral traits are heritable” • Eva Krapohl in a recent interview in The Atlantic: “Heritability describes what is; it does not predict what could be” EVSOP

  22. EVSOP

  23. ACE mediatedeffects model Koenig et al., 2007; n= 165 MZ and 100 DZ twin pairs EVSOP

  24. Biometric model fitting • Fit statistics of variousbiometric models are compared to identify the best-fitting model. • Models dependonassumptionssuch as the Equal Environments Assumption. • The EEA is oftendisputedtheoretically. • Empirical tests show it is oftenviolated. • The resulting bias, however, seems to be minor (seeFelson, Soc.Sc.Res., 2014). EVSOP

  25. Whatmoleculargeneticists do • Genome Wide Association Studies (GWAS): identify ‘candidategenes’ thatcouldexplainvariance in someoutcomevariable. • Typically, individualgeneslike OXTR and DRD4 explaintinyfractions of variance (<1%). • Typically, all single nucleotide polymorphisms (SNPs) combinedexplainlessvariance (16% of education) thanestimated in biometric models (35%) – ‘missing heritability’ problem. EVSOP

  26. Geneticists analyzed 2,165,398 single nucleotide polymorphisms and found NONE telllingus who is a friendly person https://twitter.com/renebekkers/status/806922437250011136 EVSOP

  27. Where is the socialscience? • In the varianceexplainedby shared and uniqueenvironmental factors. • Let usrule out geneticeffectsbylooking at monozygotictwinsonly. • Anydifferencebetween MZ twins must have roots in the unique environment. • Thischoiceavoidsproblemswith the EEA. • Notethat MZ twinsalso share 100% of shared environmentaleffects. EVSOP

  28. The problem • “…families whoseunobservablecharacteristicscausethem to have a high likelihood of volunteering are also more likely to educatetheirchildren, so the relationshipbetweenschooling and volunteering is just a correlationcausedbyanexcluded common cause.” John Gibson (2001) EVSOP

  29. This is notmyidea • In 2001, New Zealand economist John Gibson published a studyof volunteeringamong 85 identicaltwinpairs. • Thougheducation in the pooled sample is associatedwith more volunteering, pairwisecomparisonsreveal the opposite. • The twinwith more years of educationwas found to volunteerfewerhours. EVSOP

  30. The implication • Geneticeffectscause a positiveassociationbetweeneducation and volunteering. • Unique environmentaleffects of education on volunteering are negative in this sample. • Oneinterpretation of the negative effect is thatit is the result of the opportunitycost of volunteering, potentiallyamplifiedby a decisionmakingprocesswithin the household. EVSOP

  31. Relatedliterature • The twin fixed effects model has been used in economics to estimate the influence of schooling on income since the 1970s (Behrman & Taubman, 1976; Ashenfelter & Kreuger, 1994; Ashenfelter & Rouse, 1998; Isacsson, 1999; Miller, Mulvey & Martin, 1995; Bonjour et al., 2003). EVSOP

  32. Environment mediation model Notethatthis is a uniqueenvironment mediation model EVSOP

  33. The MIDUS data • Two wave longitudinal panel surveyonMidlife in the United States (1995 and 2005) sponsoredby the McArthur Foundation. • The RDD sample selection procedure includedtwinscreeningquestions. • Only English-speaking respondents aged 25-74 living in the US who were physically and mentally able to complete the interview were allowed to participate. EVSOP

  34. Assessingzygosity EVSOP

  35. Are twins different at all? Yes – here’s the discordancetable: Proportions of respondentsfrom the sametwin pair notreportingexactly the same level of education and religiousaffiliation EVSOP

  36. ACE model results EVSOP

  37. ACE model for volunteer hours EVSOP

  38. ACE model for volunteer hours EVSOP

  39. ACE model for volunteer hours EVSOP

  40. ACE model for volunteer hours EVSOP

  41. ACE model for volunteer hours EVSOP

  42. ACE model for volunteer hours EVSOP

  43. Remember • “Heritability describes what is; it does not predict what could be”. These are the results of educational careers and systems for those in midlife in the US. • “All human behavioral traits are heritable”. 25% is not much compared to 75% for IQ. EVSOP

  44. The highereducatedgive more These differences are massive: amountsdonated in the top category are ninetimes the amountdonated in the lowestcategory EVSOP

  45. The highereducatedvolunteer more Again, large differences – 4 to 6 times EVSOP

  46. The religiousgive more Religiousgiving is included in thisfigure. Excludingdonations to religion, the differences are much smaller. EVSOP

  47. The religiousvolunteer more Thisfigureincludesvolunteering for religiousorganizations. EVSOP

  48. Twobasicregression models • Betweeneffects model: ignores the twin pair structure, replicatesbivariate analyses. Includesgenetic + shared and uniqueenvironmentaleffects (ACE). • Within MZ twinfixedeffects model: does the highereducated / more religioustwin of an MZ pair give and volunteer more than the lesseducated / religiousco-twin? Includesonlyuniqueenvironmentaleffects. EVSOP

  49. Regressors • Church attendance (times per year) • Religious affiliation: none (reference), Catholic, Protestant, Other (0-1) • Level of education (1-12) • Strength of religiosity (z-standardized) EVSOP

  50. Education and giving EVSOP

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