Introduction
In human society, people help each other survive harsh realities. Mutual help is particularly common during emergencies in disaster situations [1, 2] and, rather than being limited to members of an established community, can also occur among strangers. During these periods, altruistic behavior predominates over egoistic behavior, bringing a sense of happiness to damaged communities in a phenomenon known as a post-disaster utopia [3].
The psychological basis of such social support is of interest in a variety of fields. The universality of social support outside of kin relationships is unique to humans and, thus, its underlying mental machinery remains the subject of ongoing discussion from various evolutionary perspectives [4-7]. Many researchers consider this type of behavior to be an enigma that is apparently contradictory to the individual propensity toward survival and have attempted to explain it by adopting various mediating social processes such as reciprocity [7], costly signaling [6], and cultural adaptation [4]. However, other researchers have taken these behaviors for granted by assuming that human survival is primarily a social, rather than an individual, process by referencing early humans. Early human populations had to overcome hostile environments by cooperating with others within a community because the necessity for group survival took precedence over intra-specific competitions [5]. Thus, understanding the role of psychological factors has also been of practical interest with respect to interventions for enhancing individual and community resilience [8, 9]. However, to date, empirical research has yet to explain fully the relationship between individual and community survival and the provision and receipt of support have only been investigated independently [10]. In fact, empirical research has yet to address actual emergency disaster situations in which the survival of individuals as well as the community both matter.
Multiple motivational and personality factors have been shown to promote helping behaviors in psychological studies over the past 50 years, with a particular focus on whether they are altruistic or egoistic [11, 12]. Behaviors can have altruistic or other-beneficial motivations that are triggered by empathic concerns for the person being helped [13-15] or by the social norms of helping [16-19]. In contrast, such behaviors may also be based on egoistic self-beneficial motives, such as the enhancement of self-esteem [20-22], acquisition of reputation [23], acquisition of personal networks or skills [24, 25], and/or the resolution of distress caused by a specific situation [26]. Egoistic motivation is typically associated with helping in the relevant context. For example, people who are oriented toward enhancing their own self-esteem help others when their own psychological need for esteem is high [20, 27] whereas those who score high for a Machiavellian personality help in the presence of others [28] and those who are sensitive to their own distress help when there is no other means of escaping their distress [29]. However, when the cost of helping is high, these egoistic motives are undermined and the influence of altruistic personality traits on behavior becomes more prominent [28, 30].
Although the personality factors that affect the receipt of support were investigated in the 1980s, few recent studies have followed-up on these findings. It has been shown that, under stressful circumstances, people with a high sense of mastery [31] or self-esteem [32] receive more social support. Other studies have suggested that different personality characteristics are related to different types of support reception. For example, personal predisposition (e.g., self-esteem), appraisal of stress, and coping strategies are related to the receipt of emotional, tangible, and informational support, respectively [33]. Furthermore, perceived social support, which is considered to be independent of the actual support that is received [34], is related to personal characteristics that are relevant to social interactions, such as social competence [35] and extraversion [36]. Perceived social support has also been associated with hardiness [37], while some suspected that the association can be attributable to age and experience, which both lead to higher levels of hardiness as well as a richer support network [38].
Although several previous works have investigated emergency situations [39-42], these studies appear to have made limited contributions to the understanding of the psychological bases of social support during emergency situations in actual large-scale disasters. First, these previous studies assessed dyadic interactions in which only the person being helped is in trouble. These situations do not appear to be comparable to disaster situations in which support providers as well as recipients are victims and both groups appraise the stressor in a similar way [43]. Second, because these studies employed situations in which an experimenter or actor pretended to be in trouble, there are limitations regarding the perceived genuineness of the situations. For example, the degree to which the participants suspected the genuineness or falsity of the situation, and reported such suspicions during debriefing as an excuse for not having helped, may be correlated with personality factors, causing a serious data selection bias [42]. Finally, these studies only addressed the provision of support and evaluated limited sets of personality traits, such as religiosity [39], responsibility denial [40], and sex roles [41, 42].
Thus, the present study aimed to determine the personality factors associated with social support during a large-scale natural disaster to elucidate more comprehensively the psychological basis of social support. The context mattered both individual and community survival, and is thought to be more relevant to situations in which human socio-psychological characteristics have been shaped throughout the history of human evolution. We analyzed the survey data of survivors of the 2011 Tohoku (or Great East Japan) earthquake and tsunami, in which more than 15,000 people were killed by a tsunami [44]. These data include evaluations of mutual social support during evacuation at the time of the earthquake; the questionnaire items pertain to helping and encouragement as well as perceived support. The other part of the dataset concerns two sets of personality factors: one set of factors that are specifically relevant to survival and another set for the Big Five personality dimensions. The former is a comprehensive set of psychological and behavioral characteristics known as “power to live” (with disasters) that has previously been identified as advantageous for survival during a disaster and includes leadership, problem-solving, altruism, stubbornness, etiquette, emotion regulation, self-transcendence, and active well-being [45].
Accordingly, the present study proposed three primary research questions. First, in the context of disaster, this study assessed whether multiple altruistic and egoistic motivations for helping [11, 12] would be activated and whether the latter would be sensitive to the cost of helping [28, 30]. Of the survival-oriented characteristics, altruism and etiquette may be categorized as altruistic helping motivations given their relevance to a higher degree of empathic concern and norm-compliance motivation, respectively. On the other hand, leadership and active well-being appear to overlap with personality factors that have previously been implicated in egoistically motivated helping [20-25]. The latter set of factors may be less relevant to the actual provision of help than to oral encouragement because egoistic motivation is undermined by the cost of helping [28, 30], such as when there is a seemingly higher cost (i.e., a risk of self-sacrifice) of actual helping in the face of an imminent tsunami. Second, the present study evaluated whether the contributions of various personal characteristics associated with support receipt [31-33, 35-37] would be replicated in a disaster context. For example, sense of mastery [31], self-esteem [32], and various coping styles [33], which have been implicated in the actual receipt of support, and hardiness [37], which has been implicated in the perceived receipt of support, appear to overlap with active well-being; it was noteworthy if the contribution of active well-being would be still valid after controlling the effect of age, which might have explained their apparent associations [38]. Furthermore, leadership, altruism, and extraversion may also be involved given their relevance to social interactions [35, 36]. Finally, we were interested in the levels that the two sets of personality factors (i.e., the power to live and the Big Five characteristics) contribute to the various aspects of social support. Although previous findings have suggested that both sets of characteristics contribute, the view that human survival is primarily a social rather than an individual process [5] may predict that survival-oriented characteristics are more relevant.
