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Adjustment Hypothesis (adjustment + hypothesis)
Selected AbstractsThe regulation of brood reduction in Booted Eagles Hieraaetus pennatus through habitat heterogeneityIBIS, Issue 4 2008EVA CASADO Brood reduction, the death of one or more chicks through siblicide or starvation, can occur through density-dependence in fecundity. Brood reduction may arise in territorial breeding systems either as a response to a high level of territorial interference in a situation of high density or as a result of habitat heterogeneity. To test the predictions of the two main hypotheses that attempt to explain how density-dependent fecundity is generated, the Habitat Heterogeneity Hypothesis (HHH) and the Individual Adjustment Hypothesis (IAH), we analysed the relationship between density and fecundity in an expanding population of Booted Eagles in Doņana National Park, Spain, using an 18-year data series. We also studied the occurrence and frequency of brood reduction in the same Booted Eagle population to appreciate further its effects and the factors that influence its occurrence and frequency. Our results support the HHH in the present situation of high density, as fecundity in the better territories (older and more frequently occupied) was higher than in low quality territories and was not affected by population density in high density periods. Nevertheless, the fecundity of high quality territories was affected (although not significantly) by population density in periods of low density, suggesting that the IAH was supported when only high quality territories were occupied. Older territories were used more frequently and chicks in these areas hatched earlier and suffered lower mortality than in new territories. We found a significant negative relationship between mean fecundity and its skewness, a finding that also supports HHH. During years of food shortage, less frequently occupied territories suffered higher rates of brood reduction. Brood reduction in this Booted Eagle population was a consequence of the heterogeneous structure of the habitat, with some territories having a higher probability of brood reduction than others. Parental nutritional condition did not affect brood reduction. The effect of brood reduction on nestling quality and population dynamics is also discussed. [source] An Assessment of the Disorderly Adjustment Hypothesis for Industrial Economies,INTERNATIONAL FINANCE, Issue 1 2006Hilary Croke Much has been written about prospects for US current account adjustment, including the possibility of what is sometimes referred to as a ,disorderly correction': a sharp fall in the exchange rate that boosts interest rates, depresses stock prices and weakens economic activity. This paper assesses some of the empirical evidence bearing on the plausibility of the disorderly adjustment scenario, drawing on the experience of previous current account adjustments in industrial economies. We examined the paths of key economic performance indicators before, during and after the onset of adjustment, building on the analysis of Freund (2000). We found little evidence among past adjustment episodes of the features highlighted by the disorderly adjustment hypothesis. Although some episodes in our sample experienced significant shortfalls in GDP growth after the onset of adjustment, these shortfalls were not associated with significant and sustained depreciations of real exchange rates, increases in real interest rates or declines in real stock prices. By contrast, it was among the episodes where GDP growth picked up during adjustment that the most substantial depreciations of real exchange rates occurred. These findings do not preclude the possibility that future current account adjustments could be disruptive, but they weaken the historical basis for predicting such an outcome. [source] Density dependence hypotheses and the distribution of fecundityJOURNAL OF ANIMAL ECOLOGY, Issue 2 2008Miguel Ferrer Summary 1Beja & Palma (2008, Journal of Animal Ecology, 77, doi: 10.1111/j.1365-2656.2007.01312.x) attempt to provide a critical analysis of the effectiveness and limitations of a previously published method (Ferrer et al. 2006, Journal of Animal Ecology, 75, 111,117.) to discriminate between Habitat Heterogeneity Hypothesis and the Individual Adjustment Hypothesis using real data from a Bonelli's eagle Hieraaetus fasciatus population. 2They conclude that significant and strong correlations between mean and CV or skewness are expected under a biologically plausible assumption about brood size distribution, and that the two hypotheses cannot therefore be distinguished. 3A major concern we have with their paper centres on this biologically plausible brood-size distribution. They used the same quasi-Poisson distribution of brood sizes (typical for a saturate population under Habitat Heterogeneity Hypothesis) for both families of simulations. So, is not surprising that both groups gave similar results. 4They argued that this approach was ,empirical', free of theoretical assumptions. But in testing between hypotheses, what we are looking for is precisely the differences among theoretical brood-size distributions predicted under the two hypotheses. 5Summarizing, with the same mean fecundity at high densities, both hypotheses must have different brood-size distributions. So the use of a single left-skewed distribution, typical of a real saturated population (most likely under Habitat Heterogeneity Hypothesis) in attempts to distinguish between the two hypotheses by re-sampling several times on the same left-skewed distribution, as done by Beja & Palma, is clearly inappropriate. [source] Mood Adjustment via Mass CommunicationJOURNAL OF COMMUNICATION, Issue 2 2003Silvia Knobloch The author has proposed and experimentally tested the mood adjustment approach, complementing mood management theory. Participants were placed in an initial mood and led to anticipate different activities after the waiting period. The upcoming activities were either dynamic or lengthy (arousal) and associated with either pleasure or performance (valence), resulting in a 2 × 2 design. During an ostensible waiting period, participants listened to choices of popular music at their will in a computer-aided procedure. This music taken from the Top 30 charts had been evaluated in a pretest for energy and joyfulness as musical qualities in order to create sets of musical selections that were either low or high in these qualities. In the experiment proper, selective exposure to energetic-joyful music as dependent measure was unobtrusively recorded via software. Results regarding self-exposure across time show that patterns of music listening differ with initial mood and anticipation, lending support to mood adjustment hypotheses. Mood management processes occurred in the beginning of the waiting period, whereas mood adjustment purposes set in toward the anticipated activity. [source] An Assessment of the Disorderly Adjustment Hypothesis for Industrial Economies,INTERNATIONAL FINANCE, Issue 1 2006Hilary Croke Much has been written about prospects for US current account adjustment, including the possibility of what is sometimes referred to as a ,disorderly correction': a sharp fall in the exchange rate that boosts interest rates, depresses stock prices and weakens economic activity. This paper assesses some of the empirical evidence bearing on the plausibility of the disorderly adjustment scenario, drawing on the experience of previous current account adjustments in industrial economies. We examined the paths of key economic performance indicators before, during and after the onset of adjustment, building on the analysis of Freund (2000). We found little evidence among past adjustment episodes of the features highlighted by the disorderly adjustment hypothesis. Although some episodes in our sample experienced significant shortfalls in GDP growth after the onset of adjustment, these shortfalls were not associated with significant and sustained depreciations of real exchange rates, increases in real interest rates or declines in real stock prices. By contrast, it was among the episodes where GDP growth picked up during adjustment that the most substantial depreciations of real exchange rates occurred. These findings do not preclude the possibility that future current account adjustments could be disruptive, but they weaken the historical basis for predicting such an outcome. [source] How to test different density-dependent fecundity hypotheses in an increasing or stable populationJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006MIGUEL FERRER Summary 1We report on a simulation study of increasing and stable populations working under two different hypotheses of density dependence of fecundity: the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH). Our aim is to find critical differences between the two regulatory hypotheses in natural populations. 2Populations under HHH show a strong negative relationship between fecundity and the coefficient of variation of fecundity. We also found a strong negative relationship between fecundity and skewness, demonstrating that, as fecundity decreases, the form of the distribution of brood sizes changes, being more left-skewed due to more territories failing to produce any offspring. 3This strong relationship was found only in the simulations of populations under HHH; whether increasing or stable, and under different ratios of good : poor territories and different population sizes. In contrast, no relationship between mean fecundity and skewness was found among simulations under IAH. 4Populations under IAH also showed a significant relationship between mean fecundity and the coefficient of variation of fecundity, but with a lower slope than in populations under HHH. 5In conclusion, skewness was found to be an adequate critical test that showed significant and strong relationships with mean fecundity only in populations under HHH, whether increasing or stable. This test is useful for species with a discrete distribution of offspring with a small number of integer categories, including most of the bird and mammal species. [source] REVIEW: The evolution of polyembryony in parasitoid waspsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 9 2010M. SEGOLI Abstract Polyembryony has evolved independently in four families of parasitoid wasps. We review three main hypotheses for the selective forces favouring this developmental mode in parasitoids: polyembryony (i) reduces the costs of egg limitation; (ii) reduces the genetic conflict among offspring; and (iii) allows offspring to adjust their numbers to the quality of the host. Using comparative data and verbal and mathematical arguments, we evaluate the relative importance of the different selective forces through different evolutionary stages and in the different groups of polyembryonic wasps. We conclude that reducing the cost of egg limitation is especially important when large broods are favoured. Reducing genetic conflict may be most important when broods are small, thus might have been important during, or immediately following, the initial transition from monoembryony to polyembryony. Empirical data provide little support for the brood-size adjustment hypothesis, although it is likely to interact with other selective forces favouring polyembryony. [source] The mental adjustment to cancer (MAC) scale: French replication and assessment of positive and negative adjustment dimensionsPSYCHO-ONCOLOGY, Issue 1 2003Sandrine Cayrou The Mental Adjustment to Cancer (MAC) scale was validated on a heterogeneous French sample of 317 cancer patients. Internal consistency was satisfactory for the original subscales (, coefficients=0.62,0.80), except for the Fatalism subscale (,=0.40). The intercorrelations of the subscales and the correlations between the subscales and Anxiety and Depression criteria were congruent with the values reported in the literature. Multidimensional Scaling revealed three positive and three negative subsets of items revealing adjustment to cancer. Congeneric factor analysis of the subsets was performed with LISREL 8.3 and only three of them (after discarding certain items) were retained: Fighting Spirit (FS) Hopelessness/Helplessness (HH) and Anxious Preoccupation (AP). A confirmatory hierarchical factor analysis on the 21 items included showed that FS measured positive adjustment to cancer and HH and AP measured negative adjustment. A differential adjustment hypothesis was proposed in order to explain the stability and instability of the measures of the diverse constructs. The three revised subscales showed the same validity pattern as the corresponding original scales, but the magnitude of the correlations was considerably improved with respect to the original subscales. The practical and the theoretical importance of FS, HH and AP are emphasized. Copyright Š 2003 John Wiley & Sons, Ltd. [source] | ||||||||||