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Dependence on a partner facilitates various types of relationship maintenance effort. In this paper, we report on two experiments in which the level of dependence was manipulated. Study 1 tested whether dependence promotes other enhancement (a form of ingratiation, whereby the likeability of the partner is positively distorted). Study 2 tested whether dependence amplifies a sense of guilt after inadvertently committing a mild form of transgression against the partner, and whether amplified guilt facilitates self-punishment. In both experiments, dependence was manipulated in a conceptually similar manner: Participants' experimental rewards were partially determined by their partner's decision. Dependence promoted other enhancement (Study 1) but did not amplify guilt, and failed to promote self-punishment (Study 2). Possible reasons for the contradictory findings of the two studies are discussed.

A previous systematic review revealed that lutein intake leads to improved cognitive function among older adults. However, the association between lutein intake and brain health remains unclear. Methods: We searched the Web of Science, PubMed, PsycInfo, and Cochrane Library for research papers. The criteria were (1) an intervention study using oral lutein intake or a cross-sectional study that examined lutein levels and the brain, (2) participants were older adults, and (3) brain activities or structures were measured using a brain imaging technique (magnetic resonance imaging (MRI) or electroencephalography (EEG)). Results: Seven studies using MRI (brain activities during rest, cognitive tasks, and brain structure) and two studies using EEG were included. We mainly focused on MRI studies. Three intervention studies using MRI indicated that 10 mg lutein intake over 12 months had a positive impact on healthy older adults’ brain activities during learning, resting-state connectivity, and gray matter volumes. Four cross-sectional studies using MRI suggested that lutein was positively associated with brain structure and neural efficiency during cognitive tasks. Conclusion: Although only nine studies that used similar datasets were reviewed, this systematic review indicates that lutein has beneficial effects on healthy older adults’ brain health.

The valuable relationships hypothesis posits that people are inclined to reconcile with their valuable-relationship partners. Focusing on a particular type of credible conciliatory signal (i.e., costly apology), the present study tested this hypothesis from the perpetrator's perspective. In studies 1 and 2, after imagining that they had committed an interpersonal transgression against one of their real friends, participants ( N =529 and 311 in studies 1 and 2, respectively) rated their willingness to incur a cost in order to apologize to the victim. Apology cost was operationalized as "canceling plans to make an apology as soon as possible" in study 1, and as "offering compensation" in study 2. The results showed that the instrumentality of the partner to achieving the participants' goals would increase their willingness to make a costly apology, after controlling for the participants' sex, version of the transgression scenario, closeness to the victim, and expected forgiveness of the victim. To ensure the external validity of this finding, studies 3 and 4 asked participants to recall one of their interpersonal transgression experiences, and to report whether they had offered compensation for it ( N =190 and 224 in studies 3 and 4, respectively). Study 3 confirmed the hypothesis, while study 4 did not directly support it. However, study 4 did show that participants were more willing to reconcile with their valuable partners. Taken together, these results indicate that the valuable relationships hypothesis applies not only to victims, but also to their perpetrators as well.

Recent experimental studies have accumulated evidence about self-punishment. In accordance with the evolutionary perspective that shame has a reputation-maintenance function, we speculated that shame would promote self-punishment. Accordingly, we tested whether proneness to shame would predict self-punishment. In the first phase of the experiment, 98 undergraduates completed the Test of Self-Conscious Affect (TOSCA), a standard measure of proneness to shame and guilt. About 2 months later, 50 of the original participants took part in a self-punishment experiment, in which they all unintentionally made an unfair resource allocation, and then had the opportunity to inflict self-punishment by abandoning some of the money they had allocated to themselves. The amount of money the participants relinquished was significantly correlated with their shame-proneness. The intensity of posttransgression shame mediated the effect of shame-proneness on self-punishment. These results provide support for the evolutionary theorization of shame as a reputation-maintenance emotion.

Curiosity is a fundamental part of human motivation that supports a variety of human intellectual behaviors ranging from early learning in children to scientific discovery. However, there has been little attention paid to the role of curiosity in aging populations. By bringing together broad but sparse neuroscientific and psychological literature on curiosity and related concepts (e.g., novelty seeking in older adults), we propose that curiosity, although it declines with age, plays an important role in maintaining cognitive function, mental health, and physical health in older adults. We identify the dopaminergic reward system and the noradrenergic system as the key brain systems implicated in curiosity processing and discuss how these brain systems contribute to the relationship between curiosity and adaptive aging.

The present study investigated a genetic underpinning of human reconciliation. Recent research has shown that people tend to inflict self-punishment as part of a repertoire of reparative acts. Since empathy generally facilitates reparative acts, we hypothesized that there exists an association between an empathy-related genetic variation, a single nucleotide polymorphism (SNP) in the oxytocin receptor ( OXTR ) gene (rs53576 A vs. G), and the tendency toward self-punishment. Participants played a modified version of the dictator game, in which they made an unfair allocation unintentionally. They then had the opportunity to punish themselves by reducing some portion of their monetary reward. The results showed that the participants with the GA or GG genotype, compared to the participants with the AA genotype, were more likely to engage in self-punishment after making the unfair allocation unintentionally. This effect was not mediated by self-critical feelings (guilt and shame) associated with the unfair allocation. The present study suggests that the OXTR polymorphism is associated with a human reconciliatory tendency.

Human friendship poses an evolutionary puzzle, since people behave more generously toward their friends than the tit-for-tat strategy stipulates. A possible explanation is that people selectively behave in a generous manner toward their true friends, but not toward fair-weather friends. Social psychological studies have suggested that people use a partner's attentiveness toward them as a cue to distinguish these two types of friends. Accordingly, it was hypothesized that people would increase their intimacy with a partner who was attentive to them. This hypothesis was tested by disentangling the frequent confounding between a partner's attention and the benefits provided by the attentive partner in two scenario experiments (studies 1a and 1b) and three laboratory experiments (studies 2a to 2c). In study 1, a partner's attentiveness was manipulated independently of the benefit provided by the partner. In study 2, the partner's attention was experimentally dissociated from any potential benefit. These studies consistently showed that the participants increased their intimacy with a partner when they received attention from the partner. This result implies that models of the evolution of friendship must incorporate information exchange regarding the valuation of the relationship, as well as the exchange of fitness-related costs and benefits.