4,036 research outputs found
Fairness and Retaliation: The Economics of Reciprocity
This paper shows that reciprocity has powerful implications for many economic domains. It is an important determinant in the enforcement of contracts and social norms and enhances the possibilities of collective action greatly. Reciprocity may render the provision of explicit incentive inefficient because the incentives may crowd out voluntary co-operation. It strongly limits the effects to competition in markets with incomplete contracts and gives rise to noncompetitive wage differences. Finally, reciprocity it is also a strong force contributing to the existence of incomplete contracts.
Cooperation and Punishment in Public Goods Experiments
This paper provides evidence that free riders are heavily punished even if punishment is costly and does not provide any material benefits for the punisher. The more free riders negatively deviate from the group standard the more they are punished. As a consequence, the existence of an opportunity for costly punishment causes a large increase in cooperation levels because potential free riders face a credible threat. We show, in particular, that in the presence of a costly punishment opportunity almost complete cooperation can be achieved and maintained although, under the standard assumptions of rationality and selfishness, there should be no cooperation at all. We also show that free riding causes strong negative emotions among cooperators. The intensity of these emotions is the stronger the more the free riders deviate from the group standard. Our results provide, therefore, support for the hypothesis that emotions are guarantors of credible threats.Voluntary cooperation, public good, punishment, emotions, social norms, experiments
Altruistic Punishment in Humans
Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the selÂźsh motives associated with signalling theory or the theory of reciprocal altruism. Here we show experimentally that the altruistic punishment of defectors is a key motive for the explanation of cooperation. Altruistic punishment means that individuals punish, although the punishment is costly for them and yields no material gain. We show that cooperation ÂŻourishes if altruistic punishment is possible, and breaks down if it is ruled out. The evidence indicates that negative emotions towards defectors are the proximate mechanism behind altruistic punishment. These results suggest that future study of the evolution of human cooperation should include a strong focus on explaining altruistic punishment.Human cooperation,Altruistic, punishment
Strong Reciprocity, Human Cooperation and the Enforcement of Social Norms
This paper provides strong evidence challenging the self-interest assumption that dominates the behavioral sciences and much evolutionary thinking. The evidence indicates that many people have a tendency to voluntarily cooperate, if treated fairly, and to punish non-cooperators. We call this behavioral propensity âstrong reciprocityâ and show empirically that it can lead to almost universal cooperation in circumstances in which purely self-interested behavior would cause a complete breakdown of cooperation. In addition, we show that people are willing to punish those who behaved unfairly towards a third person or who defected in a Prisonerâs Dilemma game with a third person. This suggests that strong reciprocity is a powerful device for the enforcement of social norms like, e.g., food-sharing norms or collective action norms. Strong Reciprocity cannot be rationalized as an adaptive trait by the leading evolutionary theories of human cooperation, i.e., by kin selection theory, reciprocal altruism theory, indirect reciprocity theory and costly signaling theory. However, multi-level selection theories and theories of cultural evolution are consistent with strong reciprocity.Strong Reciprocity, Punishment, Evolution, Human Cooperation, Social Norms
COVID-19 and the difficulty of inferring epidemiological parameters from clinical data
Knowing the infection fatality ratio (IFR) is of crucial importance for
evidence-based epidemic management: for immediate planning; for balancing the
life years saved against the life years lost due to the consequences of
management; and for evaluating the ethical issues associated with the tacit
willingness to pay substantially more for life years lost to the epidemic, than
for those to other diseases. Against this background Verity et al. (2020,
Lancet Infections Diseases) have rapidly assembled case data and used
statistical modelling to infer the IFR for COVID-19. We have attempted an
in-depth statistical review of their approach, to identify to what extent the
data are sufficiently informative about the IFR to play a greater role than the
modelling assumptions, and have tried to identify those assumptions that appear
to play a key role. Given the difficulties with other data sources, we provide
a crude alternative analysis based on the Diamond Princess Cruise ship data and
case data from China, and argue that, given the data problems, modelling of
clinical data to obtain the IFR can only be a stop-gap measure. What is needed
is near direct measurement of epidemic size by PCR and/or antibody testing of
random samples of the at risk population.Comment: Version accepted by the Lancet Infectious Diseases. See previous
version for less terse presentatio
Application of Ewald's Method for Efficient Summation of Dyon Long-Range Potentials
We study a model of dyons for SU(2) Yang-Mills theory at finite temperature T
< T_c, in particular its ability to generate a confining force between a static
quark antiquark pair. The interaction between dyons corresponds to a long-range
1/r potential, which in naive treatments with a finite number of dyons
typically gives rise to severe finite volume effects. To avoid such effects we
apply the so-called Ewald method, which has its origin in solid state physics.
The basic idea of Ewald's method is to consider a finite number of dyons inside
a finite cubic volume and enforce periodicity of this volume. We explain the
technicalities of Ewald's method and outline how the method can be applied to a
wider class of 1/r^p long-range potentials.Comment: 8 pages, 4 figures, contribution to conference "Confinement X
Strong reciprocity, human cooperation, and the enforcement of social norms
This paper provides strong evidence challenging the self-interest assumption that dominates the behavioral sciences and much evolutionary thinking. The evidence indicates that many people have a tendency to voluntarily cooperate, if treated fairly, and to punish noncooperators. We call this behavioral propensity "strong reciprocityâ and show empirically that it can lead to almost universal cooperation in circumstances in which purely self-interested behavior would cause a complete breakdown of cooperation. In addition, we show that people are willing to punish those who behaved unfairly towards a third person or who defected in a Prisoner's Dilemma game with a third person. This suggests that strong reciprocity is a powerful device for the enforcement of social norms involving, for example, food sharing or collective action. Strong reciprocity cannot be rationalized as an adaptive trait by the leading evolutionary theories of human cooperation (in other words, kin selection, reciprocal altruism, indirect reciprocity, and costly signaling theory). However, multilevel selection theories of cultural evolution are consistent with strong reciprocit
The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b
For extrasolar planets discovered using the radial velocity method, the
spectral characterization of the host star leads to a mass-estimate of the star
and subsequently of the orbiting planet. In contrast, if also the orbital
velocity of the planet would be known, the masses of both star and planet could
be determined directly using Newton's law of gravity, just as in the case of
stellar double-line eclipsing binaries. Here we report on the detection of the
orbital velocity of extrasolar planet HD209458b. High dispersion ground-based
spectroscopy during a transit of this planet reveals absorption lines from
carbon monoxide produced in the planet atmosphere, which shift significantly in
wavelength due to the change in the radial component of the planet orbital
velocity. These observations result in a mass determination of the star and
planet of 1.00+-0.22 Msun and 0.64+-0.09 Mjup respectively. A ~2 km/sec
blueshift of the carbon monoxide signal with respect to the systemic velocity
of the host star suggests the presence of a strong wind flowing from the
irradiated dayside to the non-irradiated nightside of the planet within the
0.01-0.1 mbar atmospheric pressure range probed by these observations. The
strength of the carbon monoxide signal suggests a CO mixing ratio of 1-3x10-3
in this planet's upper atmosphere.Comment: 11 Pages main article and 6 pages suppl. information: A final, edited
version appears in the 24 May 2010 issue of Natur
A Spectroscopic and Photometric Investigation of the Mercury-Manganese Star KIC 6128830
The advent of space-based photometry provides the opportunity for the first
precise characterizations of variability in Mercury-Manganese (HgMn/CP3) stars,
which might advance our understanding of their internal structure. We have
carried out a spectroscopic and photometric investigation of the candidate CP3
star KIC 6128830. A detailed abundance analysis based on newly-acquired
high-resolution spectra was performed, which confirms that the star's abundance
pattern is fully consistent with its proposed classification. Photometric
variability was investigated using four years of archival Kepler data. In
agreement with results from the literature, we have identified a single
significant and independent frequency =0.2065424 d with a
peak-to-peak amplitude of 3.4 mmag and harmonic frequencies up to .
Drawing on the predictions of state-of-the-art pulsation models and information
on evolutionary status, we discuss the origin of the observed light changes.
Our calculations predict the occurrence of g-mode pulsations at the observed
variability frequency. On the other hand, the strictly mono-periodic nature of
the variability strongly suggests a rotational origin. While we prefer the
rotational explanation, the present data leave some uncertainty.Comment: 13 pages, 13 figures, accepted for publication in MNRA
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