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To avoid polarization and maintain small-worldness in society, people who act as attitudinal brokers are critical. These people maintain social ties with people who have dissimilar and even incompatible attitudes. Based on resting-state functional magnetic resonance imaging (n = 139) and the complete social networks from two Korean villages (n = 1508), we investigated the individual-level neural capacity and social-level structural opportunity for attitudinal brokerage regarding gender role attitudes. First, using a connectome-based predictive model, we successfully identified the brain functional connectivity that predicts attitudinal diversity of respondents' social network members. Brain regions that contributed most to the prediction included mentalizing regions known to be recruited in reading and understanding others’ belief states. This result was corroborated by leave-one-out cross-validation, fivefold cross-validation and external validation where the brain connectivity identified in one village was used to predict the attitudinal diversity in another independent village. Second, the association between functional connectivity and attitudinal diversity of social network members was contingent on a specific position in a social network, namely, the structural brokerage position where people have ties with two people who are not otherwise connected.

Objectives Physical activity (PA) is an established protective factor for many chronic diseases. Numerous studies have established positive relationships between social networks and PA. Accordingly, this study examined the relationship between social network structures (specifically the network size and the number and proportion of same-sex alters) and self-reported PA in Korean middle-age adults, where the term "alter" refers to a respondent's social network members. Methods We analyzed 8,092 participants of the Cardiovascular and Metabolic Diseases Etiology Research Center cohort. We assessed the association between each network structure variable and PA level using a linear regression model. Then, we employed logistic regression to evaluate associations between social network structure and adherence to guideline-recommended exercise levels. Socio-demographic factors and health status measures were used as covariates. Results In both sexes, the social network size and proportion of same-sex network members showed positive relationships with total and moderate-to-vigorous PA. Notably, female participants with a greater number of kin were more likely to satisfy the recommended amount of total PA. Conclusions These findings suggest that large scale, same-sex intervention programs can help to achieve recommended PA regimens.

Using panel survey data with comparable variables, this study tests whether certain sets of hypotheses that are related to rational-choice and purposive-action theories of birth behavior hold in Korea as well as in Japan. In a previous study, Yamaguchi (2009) tested similar sets of hypotheses with Japanese panel data and they were largely supported. First, we clarify that although the rate of first marital birth is higher for Korea than for Japan despite the former's smaller total fertility rate (TFR), Korean women tend to delay the timing of second birth following the first birth compared with Japanese women, and the rate of third childbirth is lower for Korea than for Japan. The latter two tendencies contribute to the lower average marital birth rate in Korea than in Japan. Despite these differences, there are many commonalities between the two countries regarding the determinants of marital childbirth. The magnitude of the effects of these determinants differs between the two countries, however. First, we found that the negative interaction effect between parity and income on fertility rate predicted by Gary Becker's theory regarding the quality-price of children exists for both Japan and Korea. The theory is supported more strongly for Korea than for Japan, however. This finding indicates that policies to reduce the costs of attaining "high-quality children," such as children's educational and medical expenses, will be effective in raising fertility, but more efficiently so in Korea than in Japan. Second, we found that the availability of childcare leave increases the rate of marital fertility in both Japan and Korea. This tendency, however, holds more strongly in Japan than in Korea. Although this finding may be a result of the fact that the legally entitled term of childcare is much longer in Japan than in Korea, it nonetheless indicates that childcare leave policies in Japan were more successful than their Korean counterparts in raising fertility.

Since its first appearance in the late 1950s, Neoclassical economic theory of fertility, especially as exemplified by Gary Becker's model of household production function that assumed a unitary utility function of the household, has become one of the most popular paradigms to examine fertility changes. This paper intends to expand the economic model by incorporating the social network approach into the original paradigm. Social networks are crucial in determining the fertility rate of a society above and beyond parameters originally included in the neoclassical economic model in two ways. First, the extent that separate utilities of spouses could be treated in one function is, in part, dependent on the network embeddedness of spouses: intra-household network. If spouses are not embedded into each other's networks, it would be natural to drop the assumption of the unitary utility function and reformulate the decision process based on bargaining. Second, in addition to the intra-household network, inter-house networks also play a role in couple's decisions with regard to fertility. Couples need information about other couples' fertility decisions for their own and also normative pressures from other couples or friends are crucial in the dynamic process of fertility change. Social networks are a major conduit both for information and normative constraints. This paper focuses on the first kind of networks (intra-household networks) with illustrative empirical results by using the two waves of Korean Longitudinal Survey of Women and Families (KLOWF).