Male white-rumped munias sing syntactically simpler songs than their domestic counterparts, Bengalese finches. The differences in song structure may reflect differences in natural selection pressures between wild and domestic environments. Deacon (2010) proposed song simplicity of the wild strain could be subject to natural selection. We hypothesized the selection pressure may be species identification. Thus, we compared song variations in relation to ecological factors and dispersal history of white-rumped munias to understand song evolutionary processes. We found geographic variations of song (...) syntactical complexity. The difference of song syntactical complexity did not corresponded to genetic distance, but did to that of the proportion of mixed flocks with sympatric related species. Birds that inhabited the areas with more mixed flocks sang simpler songs. The song complexity might be constrained to intensify distinct conspecific signals from related species. Our field work provided empirical evidence supporting a proposal made by Deacon (2010). Keywords: birdsong; evolution; masking hypothesis; Bengalese finches; song geographic variation; genetic variation. (shrink)

Male white-rumped munias sing syntactically simpler songs than their domestic counterparts, Bengalese finches. The differences in song structure may reflect differences in natural selection pressures between wild and domestic environments. Deacon proposed song simplicity of the wild strain could be subject to natural selection. We hypothesized the selection pressure may be species identification. Thus, we compared song variations in relation to ecological factors and dispersal history of white-rumped munias to understand song evolutionary processes. We found geographic variations of song syntactical (...) complexity. The difference of song syntactical complexity did not corresponded to genetic distance, but did to that of the proportion of mixed flocks with sympatric related species. Birds that inhabited the areas with more mixed flocks sang simpler songs. The song complexity might be constrained to intensify distinct conspecific signals from related species. Our field work provided empirical evidence supporting a proposal made by Deacon. Keywords: birdsong; evolution; masking hypothesis; Bengalese finches; song geographic variation; genetic variation. (shrink)

Male white-rumped munias sing syntactically simpler songs than their domestic counterparts, Bengalese finches. The differences in song structure may reflect differences in natural selection pressures between wild and domestic environments. Deacon proposed song simplicity of the wild strain could be subject to natural selection. We hypothesized the selection pressure may be species identification. Thus, we compared song variations in relation to ecological factors and dispersal history of white-rumped munias to understand song evolutionary processes. We found geographic variations of song syntactical (...) complexity. The difference of song syntactical complexity did not corresponded to genetic distance, but did to that of the proportion of mixed flocks with sympatric related species. Birds that inhabited the areas with more mixed flocks sang simpler songs. The song complexity might be constrained to intensify distinct conspecific signals from related species. Our field work provided empirical evidence supporting a proposal made by Deacon. Keywords: birdsong; evolution; masking hypothesis; Bengalese finches; song geographic variation; genetic variation. (shrink)

Taking a Darwinian approach, we propose that people reason to detect free-riders on the Wason Selection task with the sharing-rule; If one receives the resource, one is an in-group member (standard), or If one is an in-group member, one receives the resource (switched). As predicted, taking the resource-provider's perspective, both undergraduates and children (11 to 12 years old) checked for the existence of out-group members taking undeserved resource. Changing the perspective to that of the resource-recipient did not alter the selection (...) pattern in undergraduates, although the prediction was that another type of free-riding -failure to share by resource-provider- would be checked as well. However, by removing confounding factors in the materials, both undergraduates and children checked for both types of free-riding, which fully supports the prediction. These results indicate that the sharing-rule elicits a thematic content effect that cannot be explained by preceding deontic reasoning theories. (shrink)