Signaling hunger through aggression-the regulation of foraging in a primitively eusocial wasp

Abstract Primitively eusocial wasps are generally headed by behaviorally dominant queens who use their aggression to suppress worker reproduction. In contrast, queens in the primitively eusocial wasp Ropalidia marginata are strikingly docile and non-aggressive. However, workers exhibit dominance-subordinate interactions among themselves. These interactions do not appear to reflect reproductive competition because there is no correlation between the relative position of an individual in the dominance hierarchy of the colony and the likelihood that she will succeed a lost/removed queen. Based on the observation that foraging continues unaltered in the absence of the queen and the correlation between dominance behavior and foraging, we have previously suggested that dominancesubordinate interactions among workers in R. marginata have been co-opted to serve the function of decentralized, self-organized regulation of foraging. This idea has been supported by an earlier experimental study where it was found that a reduced demand for food led to a significant decrease in dominance behavior. In this study, we perform the converse experiment, demonstrate that dominance behavior increases under conditions of starvation, and thus provide further evidence in support of the hypothesis that intranidal workers signal hunger through aggression

Self-Deceived Individuals Are Better at Deceiving Others

<div><p>Self-deception is widespread in humans even though it can lead to disastrous consequences such as airplane crashes and financial meltdowns. Why is this potentially harmful trait so common? A controversial theory proposes that self-deception evolved to facilitate the deception of others. We test this hypothesis in the real world and find support for it: Overconfident individuals are overrated by observers and underconfident individuals are judged by observers to be worse than they actually are. Our findings suggest that people may not always reward the more accomplished individual but rather the more self-deceived. Moreover, if overconfident individuals are more likely to be risk-prone then by promoting them we may be creating institutions, including banks and armies, which are more vulnerable to risk. Our results reveal practical solutions for assessing individuals that circumvent the influence of self-deception and can be implemented in a range of organizations including educational institutions.</p></div

Banking on cooperation: An evolutionary analysis of microfinance loan repayment behaviour

Microfinance is an economic development tool that provides loans to low-income borrowers to stimulate economic growth and reduce financial hardship. Lenders typically require joint liability, where multiple borrowers share the responsibility of repaying a group loan. We propose that this lending practice creates a cooperation dilemma similar to that faced by humans and other organisms in nature across many domains. This could offer a real-world test case for evolutionary theories of cooperation from the biological sciences. In turn, such theories could provide new insights into loan repayment behaviour. We first hypothesise how group loan repayment efficacy should be affected by mechanisms of assortment from the evolutionary literature on cooperation, i.e., common ancestry (kin selection), prior interaction (reciprocity), partner choice, similarity of tags, social learning, and ecology and demography. We then assess selected hypotheses by reviewing 41 studies from 32 countries on micro-borrowers’ loan repayment, evaluating which characteristics of borrowers are associated with credit repayment behaviour. Surprisingly, we find that kinship is mostly negatively associated with repayment efficacy, but prior interaction and partner choice are both more positively associated. Our work highlights the scope of evolutionary theory to provide systematic insight into how humans respond to novel economic institutions and interventions

Self-deception and susceptibility to being deceived are positively associated.

<p>Scatterplots with best-fit lines for residuals of susceptibility to being deceived (median of the difference between a focal individual's estimate of peer performance and the actual performance of peers) plotted against residuals of self-deception (self-estimate of focal individual's performance – focal individual's actual performance) based on absolute grades (red circles and red bold lines) and relative ranks (blue squares and blue dotted lines) in (a) week one and (b) week six. The residuals were obtained via a partial correlation analysis that regressed (i) self-deception against actual grade and (ii) susceptibility to being deceived against actual grade.</p

Summary of demographic variables of study participants.

<p>*Participants' parent's professions were assigned to categories specified by the Office of National Statistics (ONS). Occupational data from the ONS were used as a reference and the gender-specific median annual full-time London earnings of the relevant category were assigned to each parent. The earnings of both parents were added together to obtain the family income. For the partial correlation analyses, the Hollingshead four factor index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104562#pone.0104562-Hollingshead1" target="_blank">[20]</a> was derived from individual earnings (as above) for each parent and the index for the parent with the highest earnings was used as a measure of family income. The ONS table used to calculate family income was titled: PROV - Work Region Occupation SOC10 (2) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104562#pone-0104562-t003" target="_blank">Table 3</a>.7a Annual pay - Gross 2011.</p><p>Summary of demographic variables of study participants.</p

Sample sizes and sex ratios for the twelve tutorial groups included in this study.

1<p>UCL - University College London; QMUL - Queen Mary University of London.</p>2<p>Numbers in parentheses indicate the total number of students present during the tutorial since not all students chose to participate in this study.</p><p>29 students participated from UCL^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104562#nt102" target="_blank">1</a>} and 44 students from QMUL^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104562#nt102" target="_blank">1</a>} (total n = 73). The mean age ± s.d. of participants was 18.76±0.90 years and 85% were female.</p><p>Sample sizes and sex ratios for the twelve tutorial groups included in this study.</p

Self-deception and deception of others are positively associated.

<p>Scatterplots with best-fit lines for residuals of deception (median estimate of focal individual's performance by peers – focal individual's actual performance) plotted against residuals of self-deception (self-estimate of focal individual's performance – focal individual's actual performance) based on absolute grades (red circles and red bold lines) and relative ranks (blue squares and blue dotted lines) in (a) week one and (b) week six. The residuals were obtained via a partial correlation analysis that regressed (i) self-deception against actual grade and (ii) deception against actual grade. Mean ± s.d. of absolute level of self-deception was 1.93±1.54 grades and 2.11±1.70 ranks in week one and 1.72±1.42 grades and 2.04±1.99 ranks in week six. Mean ± s.d. of absolute level of deception was 1.90±1.48 grades and 1.80±1.30 ranks in week one, and 1.27±1.03 grades and 1.86±1.59 ranks in week six.</p

Boxplot of dictator donations (proportion of endowment given to receiver) according to gender for US players.

<p>Solid lines represent medians while the upper and lower boundaries of the box are the upper and lower quartiles of the data. The highest and lowest values in the data (excluding outliers) are indicated by the bars extending from the boxes.</p