Person: Nishi, Akihiro
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Nishi
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Akihiro
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Nishi, Akihiro
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Publication Intermediate Levels of Network Fluidity Amplify Economic Growth and Mitigate Economic Inequality in Experimental Social Networks(Society for Sociological Science, 2015) Nishi, Akihiro; Shirado, Hirokazu; Christakis, Nicholas A.Social connections are mutable. Prior experimental work has shown that circumstances fostering an intermediate rate of forming and breaking social ties (“network fluidity”) facilitate the maintenance of optimal levels of cooperation in experimental social networks. Previous observational work has also suggested a relationship between economic outcomes and network structure (measured statically) at a geographic level. However, it is not known how network fluidity might affect economic growth and inequality, particularly in an experimental setting. Using data from a series of online experiments involving a public goods game in 90 independent, dynamic social networks (with N=1,529 subjects), we show that increasing network fluidity simultaneously achieves the highest level of economic growth and the lowest level of economic inequality, up to a point. These effects of network fluidity on economic outcomes are mediated, in these experiments, by the levels of cooperation and tie formation that subjects evince. Finally, we show that wealthier networks are less unequal. Social network fluidity may play an important role in economic outcomes and hence in social welfare.Publication Cohort Profile: The AGES 2003 Cohort Study in Aichi, Japan(Japan Epidemiological Association, 2011) Nishi, Akihiro; Kondo, Katsunori; Hirai, Hiroshi; Kawachi, IchiroBackground: The longevity of Japanese is thought to be associated with psychosocial factors such as sense of coherence, social support, and social capital. However, the actual factors responsible and the extent of their contribution to individual health status are not known. Methods: The Aichi Gerontological Evaluation Study (AGES) 2003 Cohort Study is a prospective cohort study of community-dwelling, activities of daily living-independent people aged 65 or older living in 6 municipalities in Chita peninsula, Aichi Prefecture, Japan. Information on psychosocial factors and other individual- and community-level factors was collected in the second half of 2003 using a baseline questionnaire. Vital status and physical and cognitive decline have been followed using data derived from long-term care insurance certification. Geographical information on the study participants was also obtained. Results: A total of 13 310 (6508 men; 6802 women) study participants were registered in the study. For an interim report, we followed the cohort for 48 months, yielding 24 753 person-years of observation among men and 26 456 person-years among women. Conclusions: The AGES 2003 Cohort Study provides useful evidence for research in social epidemiology, gerontology, and health services.Publication Sex/Gender and Socioeconomic Differences in the Predictive Ability of Self-Rated Health for Mortality(Public Library of Science, 2012) Nishi, Akihiro; Kawachi, Ichiro; Shirai, Kokoro; Hirai, Hiroshi; Jeong, Seungwon; Kondo, KatsunoriBackground: Studies have reported that the predictive ability of self-rated health (SRH) for mortality varies by sex/gender and socioeconomic group. The purpose of this study is to evaluate this relationship in Japan and explore the potential reasons for differences between the groups. Methodology/Principal Findings: The analyses in the study were based on the Aichi Gerontological Evaluation Study's (AGES) 2003 Cohort Study in Chita Peninsula, Japan, which followed the four-year survival status of 14,668 community-dwelling people who were at least 65 years old at the start of the study. We first examined sex/gender and education-level differences in association with fair/poor SRH. We then estimated the sex/gender- and education-specific hazard ratios (HRs) of mortality associated with lower SRH using Cox models. Control variables, including health behaviors (smoking and drinking), symptoms of depression, and chronic co-morbid conditions, were added to sequential regression models. The results showed men and women reported a similar prevalence of lower SRH. However, lower SRH was a stronger predictor of mortality in men (HR = 2.44 [95% confidence interval (CI): 2.14–2.80]) than in women (HR = 1.88 [95% CI: 1.44–2.47]; p for sex/gender interaction = 0.018). The sex/gender difference in the predictive ability of SRH was progressively attenuated with the additional introduction of other co-morbid conditions. The predictive ability among individuals with high school education (HR = 2.39 [95% CI: 1.74–3.30]) was similar to that among individuals with less than a high school education (HR = 2.14 [95% CI: 1.83–2.50]; p for education interaction = 0.549). Conclusions: The sex/gender difference in the predictive ability of SRH for mortality among this elderly Japanese population may be explained by male/female differences in what goes into an individual's assessment of their SRH, with males apparently weighting depressive symptoms more than females.Publication Mothers and Daughters-in-Law: A Prospective Study of Informal Care-Giving Arrangements and Survival in Japan(BioMed Central, 2010) Nishi, Akihiro; Tamiya, Nanako; Kashiwagi, Masayo; Takahashi, Hideto; Sato, Mikiya; Kawachi, IchiroBackground: Daughters-in-law have played an important role in informal care-giving arrangements within East Asian traditional norms. The aim of this study was to measure the impact of daughter-in-law care-giving on the survival of care recipients. We prospectively examined the associations between different types of kinship relationship between the main family caregiver and the care recipient in relation to survival among care recipients. Methods: A questionnaire was administered to Japanese community-dwelling seniors who were eligible to receive national long-term care insurance (LTCI) community-based services. Among 191 individuals whose informal care-giving arrangement was definitively determined, we observed 58 care recipients receiving care from spouses, 58 from daughters-in-law, 27 from biological daughters, 25 from other relatives, and 23 care recipients living alone. Results: During 51 months of follow-up from December 2001, 68 care recipients died, 117 survived, and 6 moved. Hazard ratios of each care-giving arrangement were estimated by Cox proportional hazard models adjusted for care recipients' demographic factors, their care needs level based on their physical and cognitive functioning and their service use, caregivers' demographic factors, and household size. The highest risk of mortality was found for female elders receiving care from daughters-in-law (HR 4.15, 95% CI 1.02-16.90) followed by those receiving care from biological daughters (HR 1.64, 95% CI 0.37-7.21), compared to women receiving spousal care. By contrast, male elders receiving care from daughters-in-law tended to live longer than those receiving care from their spouses. Conclusions: Our finding suggests that there may be a survival "penalty" for older Japanese women who are cared for by their daughters-in-law.Publication Cooperation, decision time, and culture: Online experiments with American and Indian participants(Public Library of Science (PLoS), 2017) Nishi, Akihiro; Christakis, Nicholas A.; Rand, David G.Two separate bodies of work have examined whether culture affects cooperation in economic games and whether cooperative or non-cooperative decisions occur more quickly. Here, we connect this work by exploring the relationship between decision time and cooperation in American versus Indian subjects. We use a series of dynamic social network experiments in which subjects play a repeated public goods game: 80 sessions for a total of 1,462 subjects (1,059 from the United States, 337 from India, and 66 from other countries) making 13,560 decisions. In the first round, where subjects do not know if connecting neighbors are cooperative, American subjects are highly cooperative and decide faster when cooperating than when defecting, whereas a majority of Indian subjects defect and Indians decide faster when defecting than when cooperating. Almost the same is true in later rounds where neighbors were previously cooperative (a cooperative environment) except decision time among Indian subjects. However, when connecting neighbors were previously not cooperative (a non-cooperative environment), a large majority of both American and Indian subjects defect, and defection is faster than cooperation among both sets of subjects. Our results imply the cultural background of subjects in their real life affects the speed of cooperation decision-making differentially in online social environments.Publication Social Environment Shapes the Speed of Cooperation(Springer Nature, 2016) Nishi, Akihiro; Christakis, Nicholas A.; Evans, Anthony M.; O’Malley, A. James; Rand, David G.Are cooperative decisions typically made more quickly or slowly than non-cooperative decisions? While this question has attracted considerable attention in recent years, most research has focused on one-shot interactions. Yet it is repeated interactions that characterize most important real-world social interactions. In repeated interactions, the cooperativeness of one’s interaction partners (the “social environment”) should affect the speed of cooperation. Specifically, we propose that reciprocal decisions (choices that mirror behavior observed in the social environment), rather than cooperative decisions per se, occur more quickly. We test this hypothesis by examining four independent decision time datasets with a total of 2,088 subjects making 55,968 decisions. We show that reciprocal decisions are consistently faster than non-reciprocal decisions: cooperation is faster than defection in cooperative environments, while defection is faster than cooperation in non-cooperative environments. These differences are further enhanced by subjects’ previous behavior – reciprocal decisions are faster when they are consistent with the subject’s previous choices. Finally, mediation analyses of a fifth dataset suggest that the speed of reciprocal decisions is explained, in part, by feelings of conflict – reciprocal decisions are less conflicted than non-reciprocal decisions, and less decision conflict appears to lead to shorter decision times.