No abstract

Sexual selection may affect human altruistic behaviour. Evolutionary psychology predicts that human mate preference reflects sexual selection. We investigated sex differences in preference for opposite-sex altruism according to recipient because the reasons for altruistic behaviour differ according to the relationship between actor and recipient. We employed the Self-Report Altruism Scale Distinguished by the Recipient, which was newly developed to evaluate altruism among Japanese undergraduates. We asked participants to evaluate preferences for each item based on the recipient of the altruistic behaviour (family members, friends or acquaintances, and strangers). Preference for opposite-sex altruism differed according to recipient, gender of the participant, and relationship type, and several significant interactions were observed among these factors. We suggest that whereas women use a potential partner's altruism towards strangers as a costly signal of their resource-holding potential when choosing a mate, they consider altruism towards family when they are in a long-term relationship to ensure that resources are not allocated to non-relatives.

Men's altruism may have evolved, via female choice, as a signal of either their genetic quality or their willingness to allocate resources to offspring. The possibility that men display altruism to signal their genetic quality may be tested by examining women's preference for men's altruism across the stages of the menstrual cycle. Because women can maximize reproductive benefits by mating with men who have "good genes" on highfertility versus low-fertility days, women should show a heightened preference for male altruism on high-fertility days compared to low-fertility days, and this heightened preference should be more apparent when women evaluate men for short-term sexual relationships than for long-term committed relationships. The possibility that men display altruism to signal their willingness to provision, as opposed to their genetic quality, may be tested by examining women's preference for men's altruism toward different recipients. More specifically, altruistic behavior toward family members may reflect a willingness to provide resources for kin and, hence, willingness to provision, whereas altruistic behavior toward strangers may function as an honest signal of genetic quality. In two samples of young women (Ns = 131 and 481), we found no differences between high-and low-fertility participants in preference for men's altruism, and women preferred men's altruism more in long-term than short-term relationships. The findings suggest that men's altruistic behavior functions as a signal of willingness to provide resources rather than genetic quality.

This study describes the development and evaluation of the Self-Report Altruism Scale Distinguished by the Recipient (SRAS-DR). The relationship between an actor and a recipient is important for evolutionary studies of altruistic behavior. However, the existing scale for Japanese undergraduates does not distinguish recipients of altruistic behaviors. We developed a new self-report altruism scale based on an evolutionary viewpoint. In Study 1, undergraduate students described their altruistic behaviors in daily life, which we classified according to the recipients (family members, friends or acquaintances and strangers). Then we chose 21 items (7 items for each recipient class) to construct the SRAS-DR by using exploratory factor analyses. In Study 2, we investigated validity and reliability of the scale. The scores were significantly correlated with other relevant scales as well as with behavioral indicators. Test-retest reliability was high. These results indicate that the SRAS-DR has acceptable reliability and validity, and can be used in evolutionary studies of human altruism.

This paper presents experiments and an analysis on self-excited vibration of a plate supported by air pressure in a floating conveying machine. In this study, the instability conditions are examined by theoretical analysis in consideration of the effect of compressibility of air in a chamber. The system’s characteristic equation is derived from the plate motion coupled with equations of the gap flow between the plate and the chamber surface. The vibration characteristics and the instability conditions of the self-excited vibration are examined through experiments. The stability of the plate is affected by an air flow rate, a mass of the plate, a spring stiffness of the plate. We clarified those influences on the instability conditions of the self-excited vibration. The unsteady fluid force acting on the plate (bottom surface) is investigated by measuring the unsteady pressure. The local work done by the unsteady fluid force is also clarified. Lastly, the instability mechanism and important parameters of the self-excited vibration are discussed based on the theoretical model and experimental results.