Happy to Help? a Systematic Review and Meta-Analysis of the Effects of Performing Acts of Kindness on the Well-Being of the Acto
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Happy to help? A systematic review and meta-analysis of the effects of performing acts of kindness on the well-being of the actor Oliver Scott Curry ([email protected]) Lee Rowland Sally Zlotowitz John McAlaney Harvey Whitehouse September 2016 Abstract Does being kind make you happy? Recent advances in the behavioural sciences have provided a number of explanations of human social, cooperative and altruistic behaviour. These theories predict that people will be ‘happy to help’ family, friends, community members, spouses, and even strangers under some conditions. As a preliminary test of whether and to what extent these predictions are supported by the existing literature, here we conduct a systematic review and meta-analysis of the experimental evidence that kindness interventions (for example, performing ’random acts of kindness’) boost subjective well-being. Our initial search of the literature identifies 376 articles; of which 19 (21 studies) meet the inclusion criteria (total N=2,685). We find that the overall effect of kindness on well-being is small-to-medium (d = 0.38). There is also some indication of publication bias – lower quality studies tended to find larger effects – suggesting that the true effect size may be smaller still (0.31 ≤ d ≤ 0.34). We also find that the design and methodological limitations of existing studies preclude the testing of specific theories of kindness. We recommend that future research: distinguish between the effects of kindness to specific categories of people (for example, family, friends, strangers); take kindness- specific individual differences into account; and consider a wider range of distal outcome measures. Such research will advance our understanding of the causes and consequences of kindness, and help practitioners to maximise the effectiveness of kindness interventions. Keywords: kindness, altruism, happiness, well-being, positive psychology "1 Happy to help? A systematic review and meta-analysis of the effects of performing acts of kindness on the well-being of the actor Oliver Scott Curry ([email protected]) Lee Rowland Sally Zlotowitz John McAlaney Harvey Whitehouse September 2016 Introduction Does being kind make you happy? Does doing good make you feel good? Over the past few decades, advances in the evolutionary behavioural sciences have developed numerous theories of human social, cooperative and altruistic behaviour. These theories — kin altruism, mutualism, reciprocal altruism, and competitive altruism — make it possible to explain a variety of different ‘kinds of kindness’ (for example, love, sympathy, gratitude and heroism). And they predict that people will be ‘happy to help’ family, friends, community members, spouses, and even strangers under some conditions. More recently, there has been growing interest in using kindness as an intervention to boost ‘subjective well-being’ (including happiness, life-satisfaction and positive affect). It has been argued that altruism — acting at a cost to benefit others – benefits the altruist as well as the beneficiary. The appeal of this ‘good news story’ is obvious: if it is true that ‘helping helps the helper’, then encouraging people to be kind(er) to others could provide a simple, accessible, inexpensive, self-sustaining and effective means of tackling a variety of social problems. Here we outline existing theories of altruism and their relation to kindness, and consider the predictions these theories make about well-being. And in order to investigate whether and to what extent these predictions have been tested, and to give an overview of the literature as a whole, we conduct a systematic review and meta-analysis of the experimental studies of the effects of kind acts on the well-being of the actor. We end with a discussion of the limitations of the existing literature, and make recommendations for future research. "2 The causes of kindness Humans are social animals. Their ancestors have been living in social groups for over 50 million years (Shultz, Opie, & Atkinson, 2011), and for the past 2 million years humans have been making a living as intensely collaborative hunter-gathers (Tooby & DeVore, 1987). Social life affords numerous opportunities for mutually beneficial cooperative interactions. And humans, like other social animals, have been equipped by natural selection with a variety of traits and dispositions – love, loyalty, benevolence and bravery – that enable them to seize these opportunities. In addition, the human capacity for culture – the ability to invent and share new ways of living – has allowed them to build and elaborate upon this benevolent biological foundation, with rules, norms and other social institutions that further inculcate and amplify cooperation and altruism (Hammerstein, 2003). According to game theory – the mathematical analysis of social interaction – there is not one type of cooperation, there are many, and hence many different types of social, cooperative and altruistic behaviour (Curry, 2016; Lehmann & Keller, 2006; Nunn & Lewis, 2001; Sachs, Mueller, Wilcox, & Bull, 2004). These theories make it possible to identify and distinguish between several different ‘kinds of kindness’. People will be kind to their families Natural selection will favour altruism when the cost to the acting gene is outweighed by the benefits to copies of that gene that reside in other individuals – that is in genetic relatives or family members (Dawkins, 1979; Hamilton, 1964). As predicted by this theory of ‘kin selection’, many organisms possess adaptations for detecting and delivering benefits (or avoiding harm) to kin (Gardner & West, 2014) — the most common example being parental care of offspring (Clutton-Brock, 1991; Royle, Smiseth, & Kölliker, 2012). Humans and their recent primate ancestors have always lived in groups composed mostly of genetic relatives (Chapais, 2014; Walker, 2014), and there is evidence to suggest that they too possess adaptations for kin altruism. Humans detect kin by means of a variety of cues, including maternal perinatal association, co-residence (Lieberman, Tooby, & Cosmides, 2003, 2007), and possibly phenotype matching (DeBruine, 2005; Mateo, 2015). A preference for helping kin has been demonstrated in numerous experiments (Curry, Roberts, & Dunbar, 2013; Madsen, et al., 2007). And human kin altruism is evident in patterns of parental (Geary & Flinn, 2001) and grandparental (Euler & Weitzel, 1996) investment, as well as its absence (Daly & Wilson, 1996). It has also been argued that "3 sympathy – a sensitivity to the needs of others – originally evolved to facilitate parental care (Hublin, 2009; Preston & de Waal, 2002), before becoming available to facilitate other types of cooperation. Thus, kin selection can explain kindness in the form of love, care, sympathy and compassion. And the theory predicts that these tendencies will be elicited by others who exhibit cues of genetic relatedness, especially vulnerable children. Consistent with this perspective, research has shown that people are more generous when donating to charities using images of children with negative (sad, distressed) as opposed to neutral emotional expressions (Burt & Strongman, 2005; Small & Verrochi, 2009). People will be kind to members of their communities Natural selection will favour altruism to those with whom the actor shares a common interest – team mates, group members, coalition partners, and others who are ‘in the same boat’. Game theorists typically model such ‘mutualistic’ interactions as coordination problems (D. K. Lewis, 1969; Schelling, 1960) – including ‘stag hunts’ (Skyrms, 2004) and ‘soldiers dilemmas’ (Clutton-Brock, 2009). The benefits of ‘working together’ are evident from the ubiquity in nature of herds, shoals, flocks, and collaborative hunting (Boinski & Garber, 2000; Boos, Kolbe, Kappeler, & Ellwart, 2011), as well as the formation of alliances and coalitions (Bissonnette, et al., 2015; Harcourt & de Waal, 1992). Coordinating to mutual advantage has been a recurrent feature of the social lives of humans and their recent ancestors, especially with regard to collaborative hunting (Alvard, 2001; Alvard & Nolin, 2002), and forming coalitions to compete with rival coalitions (Wrangham, 1999). Humans have psychological adaptations for detecting coalitions by means of a variety of different ‘badges of membership’ (Kurzban, Tooby, & Cosmides, 2001; McElreath, Boyd, & Richerson, 2003; Pietraszewski, Curry, Petersen, Cosmides, & Tooby, 2015; Tooby & Cosmides, 2010); and they spontaneously form, and are altruistic to, their own groups (sometimes at the expense of other groups) (Balliet, Wu, & De Dreu, 2014; Bernhard, Fischbacher, & Fehr, 2006; Sherif, Harvey, White, Hood, & Sherif, 1954/1961; Tajfel, 1970). Coordination to mutual advantage also seems to have spurred the evolution of a sophisticated ‘theory of mind’ – the ability to think about what others are thinking and feeling (Tomasello, Carpenter, Call, Behne, & Moll, 2005; Young, Camprodon, Hauser, Pascual-Leone, & Saxe, 2010). "4 Thus, mutualism (coordination to mutual advantage) can explain kindness in the form of loyalty, solidarity, camaraderie, civic-mindedness, community spirit, and commitment to a cause ‘greater than oneself’. And the theory predicts that these tendencies will be elicited by other members of the groups with which one identifies (including strangers) (Whitehouse & Lanman, 2014). Consistent with this perspective, research has demonstrated that geographical proximity (and perhaps perceptions