|
| ||
|
|
||
Central Assumption (central + assumption)
Selected AbstractsEMPIRICAL COMPARISON OF G MATRIX TEST STATISTICS: FINDING BIOLOGICALLY RELEVANT CHANGEEVOLUTION, Issue 10 2009Brittny Calsbeek A central assumption of quantitative genetic theory is that the breeder's equation (R=GP,1S) accurately predicts the evolutionary response to selection. Recent studies highlight the fact that the additive genetic variance,covariance matrix (G) may change over time, rendering the breeder's equation incapable of predicting evolutionary change over more than a few generations. Although some consensus on whether G changes over time has been reached, multiple, often-incompatible methods for comparing G matrices are currently used. A major challenge of G matrix comparison is determining the biological relevance of observed change. Here, we develop a "selection skewers"G matrix comparison statistic that uses the breeder's equation to compare the response to selection given two G matrices while holding selection intensity constant. We present a bootstrap algorithm that determines the significance of G matrix differences using the selection skewers method, random skewers, Mantel's and Bartlett's tests, and eigenanalysis. We then compare these methods by applying the bootstrap to a dataset of laboratory populations of Tribolium castaneum. We find that the results of matrix comparison statistics are inconsistent based on differing a priori goals of each test, and that the selection skewers method is useful for identifying biologically relevant G matrix differences. [source] Evolutionary ecology, sexual conflict, and behavioral differentiation among baboon populationsEVOLUTIONARY ANTHROPOLOGY, Issue 5 2003Peter Henzi Abstract A central assumption of baboon socio-ecological models is that all populations have the same capacity to react to different environments. The burden of our argument is that this assumption needs to be reconsidered. Data suggest not only that hamadryas, but chacma as well, differ in interesting ways from the stock baboon model that has been derived, in the main, from earlier work on anubis and cynocephalus. Although environmental factors are behind these differences, much of their influence is a consequence of their effect on restricted ancestral populations, where selection for appropriate responses to the social challenges set by local conditions now constrains the nature of individual responses to contemporary environments. Available genetic evidence suggess a southern African origin for Papio at a time when climatic conditions were certainly no better than they are now and when temperatures, if nothing else, were probably lower. In light of this, a reconstruction of how climate has structured the sexual conflict between males and female charcma, which itself hinges on infanticide, can help explain not only the East African pattern, but also how the apparently anomalous hamadryas pattern has been derived. [source] PERFORMANCE MANAGEMENT AND BEST VALUE AUDIT IN SCOTLAND: A RESEARCH NOTE ON THEORY AND PRACTICEFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 4 2008Arthur Midwinter This paper appraises the theory and practice of Best Value Audit in Scotland, and in particular the central assumption that a robust performance management system is essential for continuous improvement in service delivery, within a rational planning model of governance. The reviews of Best Value Audit in practice reveal important gaps between theory and practice, with an overemphasis on monitoring process rather than performance. There is, therefore, considerable scope to reduce the demands of the audit process on local government, and Best Value Audit, needs to move from a theoretical model to an evidence-based model of good practice if real progress is to be made. [source] Predators, parasitoids and pathogens: species richness, trophic generality and body sizes in a natural food webJOURNAL OF ANIMAL ECOLOGY, Issue 1 2000J. Memmott Summary 1.,A food web is presented which describes trophic interactions among the herbivores, parasitoids, predators and pathogens associated with broom, Cytisus scoparius (L.) Link. The data come from published work on the community at a single site. The web comprises a total of 154 taxa: one plant, 19 herbivores, 66 parasitoids, 60 predators, five omnivores and three pathogens. There are 370 trophic links between these taxa in the web. The taxa form 82 functionally distinct groups, called trophic species. 2.,Predators consumed significantly more species than did parasitoids: a median of two prey species per species of predator (range = 1,9), compared to a median of one host species per species of parasitoid (range = 1,4). Significant differences in the number of species consumed were also found among the five predator groups: birds (median = 4), spiders (median = 5), Coleoptera (median = 1), Diptera (median = 2) and Hemiptera (median = 7). 3.,Vulnerability, measured by numbers of consumer species, was significantly affected by the herbivores' feeding styles: externally feeding herbivores were most vulnerable and the concealed herbivores were least vulnerable. Miners were vulnerable to the most parasitoid species and externally feeding herbivores were the most vulnerable to predators. 4.,Resource species had a median vulnerability of 13 consumer species, a figure far higher than that in most published food webs. No significant relationship was found between species' vulnerability to predators and vulnerability to parasitoids. However, there was a strong negative relationship between the percentage mortality due to predation and percentage mortality due to parasitism. 5.,The broom food web contains nine orders of insects, a figure higher than previously recorded. The web also contains vertebrates, arachnids, bacteria and fungi. Most of the interactions between the orders were weak. Connectance was calculated for the complete web, the parasitoid sub-web and the predator sub-web. The connectance of the predator sub-web, a value of 0·0364, was more than an order of magnitude larger than the connectance of the entire web (0·0156) or the parasitoid sub-web (0·018). 6.,The body lengths of 52 species in the food web were estimated from field guides or museum specimens. Larger predators consumed smaller prey in 93% of predator,prey interactions. Smaller parasitoids consumed larger hosts in 79% of parasitoid,host interactions. Parasitoids were significantly smaller than predators. 7.,The 52 species were arranged in order of increasing body length along the columns and down the rows of a food web matrix. The predator sub-web was predominantly upper triangular with 8% of non-zero elements falling below the leading diagonal. The parasitoid sub-web was predominantly lower triangular with 21% non-zero elements falling above the leading diagonal. The entire web contains entries both above and below the main diagonal and thus violates a central assumption of the cascade model. [source] The importance of growth and mortality costs in the evolution of the optimal life historyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2006D. A. ROFF Abstract A central assumption of life history theory is that the evolution of the component traits is determined in part by trade-offs between these traits. Whereas the existence of such trade-offs has been well demonstrated, the relative importance of these remains unclear. In this paper we use optimality theory to test the hypothesis that the trade-off between present and future fecundity induced by the costs of continued growth is a sufficient explanation for the optimal age at first reproduction, ,, and the optimal allocation to reproduction, G, in 38 populations of perch and Arctic char. This hypothesis is rejected for both traits and we conclude that this trade-off, by itself, is an insufficient explanation for the observed values of , and G. Similarly, a fitness function that assumes a mortality cost to reproduction but no growth cost cannot account for the observed values of ,. In contrast, under the assumption that fitness is maximized, the observed life histories can be accounted for by the joint action of trade-offs between growth and reproductive allocation and between mortality and reproductive allocation (Individual Juvenile Mortality model). Although the ability of the growth/mortality model to fit the data does not prove that this is the mechanism driving the evolution of the optimal age at first reproduction and allocation to reproduction, the fit does demonstrate that the hypothesis is consistent with the data and hence cannot at this time be rejected. We also examine two simpler versions of this model, one in which adult mortality is a constant proportion of juvenile mortality [Proportional Juvenile Mortality (PJM) model] and one in which the proportionality is constant within but not necessarily between species [Specific Juvenile Mortality (SSJM) model]. We find that the PJM model is unacceptable but that the SSJM model produces fits suggesting that, within the two species studied, juvenile mortality is proportional to adult mortality but the value differs between the two species. [source] Progressive stage transition does mean getting better: a further test of the Transtheoretical Model in recovery from alcohol problemsADDICTION, Issue 6 2009Nick Heather ABSTRACT Aims To test two central assumptions of the Transtheoretical Model (TTM) regarding recovery from alcohol problems: (i) individuals making a forward transition from pre-action to action stages will show greater drinking improvements than those remaining in pre-action stages; and (ii) individuals remaining in pre-action stages will not demonstrate improvements in drinking outcomes. Design and setting Large, multi-centre, randomized controlled trial of treatment for alcohol problems [United Kingdom Alcohol Treatment Trial (UKATT)]. Measurements Stage of change, drinks per drinking day and percentage days abstinent at baseline, 3- and 12-month follow-ups. Findings In support of TTM assumption 1, improvements in drinking outcomes were consistently greater among clients who showed a forward stage transition (Cohen's d = 0.68) than among those who did not (d = 0.10). Two tests of assumption 2 showed a significant improvement in drinking outcomes in non-transition groups, inconsistent with the TTM; one test showed a significant deterioration and the other showed equivalent drinking outcomes across time. An explanation is offered as to why, under the relevant assumption of the TTM, clients in non-transition groups showed small changes in drinking outcomes. Conclusions In contrast to a previous study by Callaghan and colleagues, our findings largely support the TTM account of recovery from alcohol problems in treatment. The discrepancy can be explained by the use in our study of a more reliable and valid method for assigning stage of change. [source] Does progressive stage transition mean getting better?ADDICTION, Issue 10 2007A test of the Transtheoretical Model in alcoholism recovery ABSTRACT Aims To test two central assumptions of stage movement in the Transtheoretical Model (TTM) vis-à-vis alcoholism recovery: (assumption 1) individuals making a forward transition to the action-oriented stages (i.e. preparation/action) will manifest relatively greater drinking improvements than their counterparts remaining in the pre-action stages (i.e. pre-contemplation, contemplation); and (assumption 2) individuals remaining in the pre-action stages across time will not demonstrate clinically relevant improvement in drinking outcomes. Design and setting Secondary data analyses of data from Project MATCH, a large multi-site alcoholism treatment-matching study. Measurements At baseline and 3 months post-treatment, the following variables were measured: stage-of-change (based on the University of Rhode Island Change Assessment measure and the most recent stage assignment algorithm), drinks per drinking day (DDD) and percentage days abstinent (PDA). Findings Six of the eight tests of assumptions 1 and 2 failed to support the basic tenets of the TTM. Our study demonstrated that individuals making a progressive stage transition to the action-oriented stages (i.e. preparation/action) do not necessarily manifest greater improvements in drinking-related behavior than individuals remaining in the pre-action stages (i.e. pre-contemplation, contemplation), and that individuals remaining in the pre-action stages over time actually do manifest statistically significant and clinically important improvements in drinking-related behavior. Conclusions Our findings challenge not only the criterion validity associated with stage movement in the TTM account of alcoholism recovery, but also recent TTM-based substance abuse treatment approaches which systematically promote forward stage transition as a primary clinical goal and marker of therapeutic success. [source] Kafka, Critical Theory, Dialectical Theology: Adorno's Case against Hans-Joachim SchoepsGERMAN LIFE AND LETTERS, Issue 2 2010Margarete Kohlenbach ABSTRACT Theodor Adorno derived from his reading of Kafka some of the central assumptions that inform the critical theory of the Frankfurt School. He opposed theological Kafka interpretations in general, and in particular rejected Hans-Joachim Schoeps's reading of Kafka in the context of Karl Barth's dialectical theology. Adorno and Schoeps thus came to exemplify the dichotomy with which we still characterise the early reception of Kafka's work as either secular (sociological or political) or theological and religious. The disintegration of religion as a comprehensive social system in twentieth-century Germany means that writers can agree with traditional theology and religion in some regards while opposing them in others. This article argues that any unqualified adoption of the dichotomy between the secular and the religious is detrimental to our understanding of both Kafka's work and its early reception. First, the article outlines some of the major discrepancies in Kafka's heterogeneous engagements with religion. Second, it places Adorno's rejection of Schoeps's interpretation in the political context of National Socialism and the Holocaust. Finally, it compares Adorno's notion of ,inverse theology' with Schoeps's inversion of salvation history. Throughout, the article aims to ascertain the differences as well as the underlying commonalities between Adorno's and Schoeps's Kafka reception. Wesentliche Richtlinien der Kritischen Theorie der Frankfurter Schule verdanken sich der Kafka-Rezeption Adornos, die theologische Deutungen Kafkas im allgemeinen abweist und insbesondere Hans-Joachim Schoeps' Verständnis von Kafkas Werk im Kontext der Dialektischen Theologie Karl Barths verwirft. Adorno und Schoeps repräsentieren die Pole einer Dichotomie, mit der noch heute die Beiträge der frühen Kafka-Rezeption entweder als soziologisch und politisch oder als theologisch und religiös klassifiziert werden. Die Desintegration religiösen Lebens in der deutschen Gesellschaft des 20. Jahrhunderts bringt es mit sich, dass Schriftsteller in jeweils bestimmten Hinsichten traditionelle Theologie und Religion verwerfen,und,übernehmen können. Der vorliegende Beitrag argumentiert, dass jede nicht-spezifizierte Vorstellung einer Dichotomie von religiösem und weltlichem Leben und Denken aufgegeben werden muss, wenn wir Kafkas Werk und seine frühe Rezeption verstehen wollen. Der Beitrag skizziert zunächst zentrale Diskrepanzen in Kafkas heterogenen Bezugnahmen auf Religiöses. Im Anschluss stellt er Adornos Schoeps-Kritik in den politischen Kontext von Nationalsozialismus und Holocaust. Wie der Beitrag als ganzer soll der abschließende Vergleich der Begiffe ,inverse Theologie' (Adorno) und ,Unheilsgeschichte' (Schoeps) ein angemessenes Verständnis der Unterschiede und Gemeinsamkeiten in der Kafka-Deutung der beiden Autoren ermöglichen. [source] Overeducation in the Labour MarketJOURNAL OF ECONOMIC SURVEYS, Issue 3 2006Séamus McGuinness Abstract., This paper presents a review of the literature on overeducation. The paper assesses the consistency of overeducation within the context of a number of theoretical frameworks including Human Capital Theory (HCT) and Assignment Theory. The analysis goes on to discuss the various measurement controversies associated with the study of overeducation in order to provide an assessment of the extent to which the impacts of the phenomenon represent an economic reality as opposed to a statistical artefact. After reviewing the literature, it is concluded that the impacts of overeducation are likely to be non-trivial and that the phenomenon may potentially be costly to individuals and firms, as well as the economy more generally. The existence of overeducation also raises some doubts with respect to the validity of some of the central assumptions and predictions of HCT that are unlikely to be fully explained by gaps in the standard wage equation framework. [source] | |||||||||||||