When are Women More Generous than Men?

Previous research on gender differences in behavior has led to seemingly contradictory findings about generosity. From data generated by 290 subject pairs, we find that women are more sensitive than men to the costs of generous actions when deciding whether or not to be generous. The factors that affect the level of generosity observed in our experiments are reciprocal motivation, the level of money payoffs, and the level of social distance in the experimental protocol. The relatively greater sensitivity of women to the costs of generous behavior can explain most of the apparent inconsistencies in previously-reported findings.

Assigning Intentions when Actions are Unobservable: the Impact of Trembling in the Trust Game

This paper reports laboratory experiments investigating behavior when players may make inferences about the intentions behind others' prior actions based on higher- or lower-accuracy information about those actions. We investigate a trust game with first mover trembling, a game in which nature determines whether the first mover's decision is implemented or reversed. The results indicate that second movers give first movers the benefit of the doubt. However, first movers do not anticipate this response. Ultimately, it appears that subjects are thinking on at least three levels when making decisions: they are concerned with their own material well being, the trustworthiness of their counterpart, and how their own actions will be perceived.

Turnover of nitrogen during decomposition of corn and soybean residue in soil

Mineralization and immobilization of N often occur simultaneously in soils, and this results in a turnover of N within pools of inorganic and organic N. Measurement of mineralization-immobilization turnover provides important information about N transformations in soil. Failure to consider the effects of this turnover, however, introduces errors in interpretations of [superscript]15N-tracer studies of transformations and movement of N in soils. Laboratory studies were conducted under controlled conditions to learn more about factors affecting amounts of turnover of N in soils used for corn production;Studies involving additions of various amounts of corn residue and [superscript]15N-labeled nitrate showed that mineralization-immobilization turnover was largely the result of sequential immobilization and mineralization rather than simultaneous processes. Moreover, availability of N in soil influenced rates of immobilization and microbial growth efficiencies occurring during the initial stages of decomposition, rates of mineralization occurring during the latter stages of decomposition, and the amount of turnover that occurred. These observations offer a rational explanation for existing confusion associated with phenomena often called priming effects and added N interactions. Studies showed that fixation and release of ammonium from clay minerals is another source of turnover of N in soils and that failure to recognize this turnover can result in an overestimation of mineralization-immobilization turnover;Studies of mineralization-immobilization turnover in soils having varied cropping histories showed that the period of immobilization during the early stages of decomposition varied in length and could extend into the next cropping season under field conditions. Observed differences in rates and amounts of immobilization during the decomposition of corn and soybean residues provide a reasonable explanation as to why corn grown after soybean requires less fertilizer than does corn grown after corn. They also provide a rational explanation as to why high rates of N fertilization promote loss of soil organic matter. Overall, the results demonstrate that a better understanding of the factors affecting mineralization-immobilization turnover in soils should help predict N availability within cropping seasons and the changes in concentrations of soil organic matter that occur across many cropping seasons

Assigning Intentions when Actions are Unobservable: the Impact of Trembling in the Trust Game

This paper reports laboratory experiments investigating behavior when players may make inferences about the intentions behind others’ prior actions based on higher- or lower-accuracy information about those actions. We investigate a trust game with first mover trembling, a game in which nature determines whether the first mover’s decision is implemented or reversed. The results indicate that second movers give first movers the benefit of the doubt. However, first movers do not anticipate this response. Ultimately, it appears that subjects are thinking on at least three levels when making decisions: they are concerned with their own material well being, the trustworthiness of their counterpart, and how their own actions will be perceived

Thrifty Viability and Traditional Mortgage Lending: A Simultaneous Equations Analysis of the Risk-Return Trade-Off

A number of studies have argued that the thrift industry is not viable as it is presently structured and regulated because mortgage yields are inadequate to cover interest and operating costs. This hypothesis suggests that observed profitability is primarily the result of the tendency of the industry to "ride" the yield curve by borrowing short and lending long. To evaluate this argument, we construct a simultaneous-equations model of thrift risk (maturity gap positions) and return (net interest margin). We find support for the notion that the industry could not be reasonably profitable if it did not take on significant interest-rate risk. For instance, a zero gap position produces a return on assets of only 19 basis points and a return on equity of only 4%. We also estimate the amount of interest-rate risk the industry can employ to increase returns on equity and assets. Our estimates show that over 50% of thrift profits earned during this period are the result of negative gap positions and interest-rate speculation. As earlier research shows, changes in regulations affecting thrift asset and liability choices can be counterproductive.

When are Women More Generous than Men?

Previous research on gender differences in behavior has led to seemingly contradictory findings about generosity. From data generated by 290 subject pairs, we find that women are more sensitive than men to the costs of generous actions when deciding whether to be generous. The factors that affect the level of generosity observed in our experiments are reciprocal motivation, the level of money payoffs, and the level of social distance in the experimental protocol. The relatively greater sensitivity of women to the costs of generous behavior can explain most of the apparent inconsistencies in previously reported findings. (JE

Characterisation of bacterioplankton communities in the meltwater ponds of Bratina Island, Victoria Land, Antarctica

A unique collection of Antarctic aquatic environments (meltwater ponds) lies in close proximity on the rock and sediment-covered undulating surface of the McMurdo Ice Shelf, near Bratina Island (Victoria Land, Antarctica). During the 2009–10 mid-austral summer, sets of discrete water samples were collected across the vertical geochemical gradients of five meltwater ponds (Egg, P70E, Legin, Salt and Orange) for geochemical and microbial community structure analysis. Bacterial DNA fingerprints (using Automated Ribosomal Intergenic Spacer Analysis) statistically clustered communities within ponds based on ANOSIM (R = 0.766, P = 0.001); however, one highly stratified pond (Egg) had two distinct depth-related bacterial communities (R = 0.975, P = 0.008). 454 pyrosequencing at three depths within Egg also identified phylum level shifts and increased diversity with depth, Bacteroidetes being the dominant phyla in the surface sample and Proteobacteria being dominant in the bottom two depths. BEST analysis, which attempts to link community structure and the geochemistry of a pond, identified conductivity and pH individually, and to a lesser extent Ag109, NO2 and V51 as dominant influences to the microbial community structure in these ponds. Increasing abundances of major halo-tolerant OTUs across the strong conductivity gradient reinforce it as the primary driver of community structure in this stud

Benthic microbial communities of coastal terrestrial and ice shelf Antarctic meltwater ponds.

The numerous perennial meltwater ponds distributed throughout Antarctica represent diverse and productive ecosystems central to the ecological functioning of the surrounding ultra oligotrophic environment. The dominant taxa in the pond benthic communities have been well described however, little is known regarding their regional dispersal and local drivers to community structure. The benthic microbial communities of 12 meltwater ponds in the McMurdo Sound of Antarctica were investigated to examine variation between pond microbial communities and their biogeography. Geochemically comparable but geomorphologically distinct ponds were selected from Bratina Island (ice shelf) and Miers Valley (terrestrial) (<40 km between study sites), and community structure within ponds was compared using DNA fingerprinting and pyrosequencing of 16S rRNA gene amplicons. More than 85% of total sequence reads were shared between pooled benthic communities at different locations (OTU0.05), which in combination with favorable prevailing winds suggests aeolian regional distribution. Consistent with previous findings Proteobacteria and Bacteroidetes were the dominant phyla representing over 50% of total sequences; however, a large number of other phyla (21) were also detected in this ecosystem. Although dominant Bacteria were ubiquitous between ponds, site and local selection resulted in heterogeneous community structures and with more than 45% of diversity being pond specific. Potassium was identified as the most significant contributing factor to the cosmopolitan community structure and aluminum to the location unique community based on a BEST analysis (Spearman's correlation coefficient of 0.632 and 0.806, respectively). These results indicate that the microbial communities in meltwater ponds are easily dispersed regionally and that the local geochemical environment drives the ponds community structure