The reputation of punishers

Punishment is a potential mechanism to stabilise cooperation between self-regarding agents. Theoretical and empirical studies on the importance of a punitive reputation have yielded conflicting results. Here, we propose that a variety of factors interact to explain why a punitive reputation is sometimes beneficial and sometimes harmful. We predict that benefits are most likely to occur in forced play scenarios and in situations where punishment is the only means to convey an individual's cooperative intent and willingness to uphold fairness norms. By contrast, if partner choice is possible and an individual's cooperative intent can be inferred directly, then individuals with a nonpunishing cooperative reputation should typically be preferred over punishing cooperators

Sorption of Phosphate onto Surfactant-Modified Zeolite Particles

Slow-release phosphorous (P) fertilizer is basically considered as an approach to increase the efficiency of P fertilization on agricultural lands. This study aimed to examine the effect of pH solutions (3.5, 7, 9 and 11), contact times (10, 15, 30, 60, 90, 120 and 150 minutes), and solid-solution ratios (1:500 , 1:1000, and 1:1500) on the capability of zeolite as a material for the development of slow-release fertilizers for absorbing phosphate ions. The surface of natural zeolite was chemically modified through surfactant addition (hexadecyltrimethylammonium bromide - C9H42BrN or HDTMABr), and the capability of surfactant-modified zeolite (SMZ) to adsorb phosphate ions was studied through batch experiments. Results of the study showed that pH solution affected the sorption of phosphate ions onto SMZ, in which pH solution of 5.0 showed high P adsorption and was below the pHpzc of SMZ. The amount of adsorbed P onto SMZ does not vary based on changes in contact time. Result of the study also revealed that the maximum sorption capacity (Qmax) of phosphate ions onto SMZ increases with increasing solid-solution ratios. Results of this study show that SMZ may potentially be used as an material for the development of slow-release P fertilizers, in which the pH solution and solid-solution ratio control the amount of sorbed P onto SMZ

Power asymmetries and punishment in a prisoner's dilemma with variable cooperative investment

In many two-player games, players that invest in punishment finish with lower payoffs than those who abstain from punishing. These results question the effectiveness of punishment at promoting cooperation, especially when retaliation is possible. It has been suggested that these findings may stem from the unrealistic assumption that all players are equal in terms of power. However, a previous empirical study which incorporated power asymmetries into an iterated prisoner's dilemma (IPD) game failed to show that power asymmetries stabilize cooperation when punishment is possible. Instead, players cooperated in response to their partner cooperating, and punishment did not yield any additional increase in tendency to cooperate. Nevertheless, this previous study only allowed an all-or-nothing–rather than a variable–cooperation investment. It is possible that power asymmetries increase the effectiveness of punishment from strong players only when players are able to vary their investment in cooperation. We tested this hypothesis using a modified IPD game which allowed players to vary their investment in cooperation in response to being punished. As in the previous study, punishment from strong players did not increase cooperation under any circumstances. Thus, in two-player games with symmetric strategy sets, punishment does not appear to increase cooperation

Keragaman Karakter Varietas Lokal Padi Pasang Surut Kalimantan Selatan

Artificial mutation could be used in the formation of base population for selection. Local varieties which have a wide distance of relationship are expected to have a greater opportunity for obtaining more diverse offspring. The purpose of this study was to select five distinct local tidal swamp rice varieties of South Kalimantan that could be used for parental mutation. The study was conducted from March to December 2009. The distance of varietal relationship was estimated by cluster analysis using the SPSS Programme Version 11.5. Selection of the five best varieties was carried out by the Exponential Rank Method (ERM) applying 7 criteria, namely plant height, number of panicles, panicle length, grain weight/panicle, number of grains/panicle, weight of 1000 grains, and grain yield. Results of the cluster analysis based on a 82.5% similarity level showed that diversities of the 40 accessions of local tidal swamp rice in South Kalimantan were spread in four clusters, namely Cluster I (13 varieties), Cluster II (1 varieties), Cluster III (6 varieties) , and Cluster IV (20 varieties). Five varieties that were selected based on the cluster analysis and the ERM were Siam Harli, Siam Unus (Bumi Makmur), Siam Kuatek, Datu, dan Siam Unus (Barambai)

Punishment and cooperation in nature.

Humans use punishment to promote cooperation in laboratory experiments but evidence that punishment plays a similar role in non-human animals is comparatively rare. In this article, we examine why this may be the case by reviewing evidence from both laboratory experiments on humans and ecologically relevant studies on non-human animals. Generally, punishment appears to be most probable if players differ in strength or strategic options. Although these conditions are common in nature, punishment (unlike other forms of aggression) involves immediate payoff reductions to both punisher and target, with net benefits to punishers contingent on cheats behaving more cooperatively in future interactions. In many cases, aggression yielding immediate benefits may suffice to deter cheats and might explain the relative scarcity of punishment in nature

The benefits of being seen to help others: indirect reciprocity and reputation-based partner choice

When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans. This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’

The psychological foundations of reputation-based cooperation

Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here, we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others' mental states (which allows for perspective-taking and attribution of intentions) and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation. This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’

The benefits of being seen to help others: indirect reciprocity and reputation-based partner choice

When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans.Social decision makin