Humans actively share resources with one another to a much greater degree than do other great apes, and much human sharing is governed by social norms of fairness and equity. When in receipt of a windfall of resources, human children begin showing tendencies towards equitable distribution with others at five to seven years of age. Arguably, however, the primordial situation for human sharing of resources is that which follows cooperative activities such as collaborative foraging, when several individuals must share the spoils of their joint efforts. Here we show that children of around three years of age share with others much more equitably in collaborative activities than they do in either windfall or parallel-work situations. By contrast, one of humans' two nearest primate relatives, chimpanzees (Pan troglodytes), 'share' (make food available to another individual) just as often whether they have collaborated with them or not. This species difference raises the possibility that humans' tendency to distribute resources equitably may have its evolutionary roots in the sharing of spoils after collaborative efforts.
To address a controversy in the literature concerning whether monkeys show an aversion to inequity, individuals of a New World monkey species, cotton top tamarins (Saguinus oedipus) were tested in an offering task and in a bartering task. At issue was whether the monkeys rejected rewards because of a violation of expectancy of the preferred reward, or whether they rejected rewards because of a sensitivity to socially mediated inequity. The data from both tasks indicated that the subjects were more likely to reject when preferred rewards were presented, either because of another animal eating the reward (the social condition) or because of rewards being presented but inaccessible. The bartering task led to the only behavioral indication of aversion due specifically to social inequity, which was demonstrated when tamarins' sensitivity to the difference in rewards increased with exposure to other tamarins working to receive the preferred rewards. The results suggest that social inequity aversion will be assessed by tamarins, and possibly by other primates, only under conditions of limited resources and a requirement of work, which may make the situation a bit more competitive and thus drives attention toward both social and reward evaluation.
Objective: This study reports the efficacy and safety of zoledronic acid (ZOL) in preventing bone loss in postmenopausal patients receiving an aromatase inhibitor (AI) following tamoxifen. Methods: Postmenopausal patients with stage I–III hormone receptor-positive breast cancer who received tamoxifen for 2.5–3 years were randomized to receive letrozole (2.5 mg/day) with (n = 47) or without (n = 43) ZOL (4 mg i.v. every 6 months) for 2 years. The primary endpoint was percent change from baseline in lumbar spine (LS) bone mineral density (BMD) up to 60 months. Results: Ninety patients (86 evaluable) with a median age of 59 years (42.9–83.6), 50/86 of whom had previously been treated with chemotherapy, were followed for a median time of 41.4 months. While the control group showed a significant decrease in LS T-score (p = 0.0005), the ZOL group presented an increase over time (p = 0.0143). Change over time in LS T-score was significantly different between groups, favoring ZOL (p < 0.0001 at 24 and 48 months). No fractures, renal dysfunction or osteonecrosis of the jaw were reported. The toxicity profile was similar to those previously reported for each drug. Conclusion: The addition of ZOL to letrozole was safe and efficacious in maintaining LS BMD in postmenopausal patients with hormone receptor-positive breast cancer and who were receiving letrozole following 2.5–3 years of tamoxifen.
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