Home About us Contact
|
Home About us Contact | ||
|
|
||
First Empirical Test (first + empirical_test)
Selected AbstractsHow Does the Comforting Process Work?HUMAN COMMUNICATION RESEARCH, Issue 3 2006An Empirical Test of an Appraisal-Based Model of Comforting Burleson and Goldsmith's (1998) comforting model suggests an appraisal-based mechanism through which comforting messages can bring about a positive change in emotional states. This study is a first empirical test of three causal linkages implied by the appraisal-based comforting model. Participants (N = 258) talked about an upsetting event with a confederate trained to display low, moderate, or high levels of person centeredness and nonverbal immediacy. After the conversation, participants completed several scales. Latent composite structural equation modeling was used to examine the model, which showed that person-centered and immediate emotional support exerted a direct effect on emotional improvement. Above and beyond this direct effect, person-centered comfort also encouraged people to verbalize their thoughts and emotions. These verbalizations facilitated cognitive appraisals, which in turn exerted a strong direct effect on emotional improvement. Mediation analyses further suggested that verbalizations of positive emotion words in conjunction with reappraisals partially mediated the influence of person-centered comfort on emotional improvement. [source] An experimental test for effects of the maternal environment on delayed germinationJOURNAL OF ECOLOGY, Issue 5 2010Katja Tielbörger Summary 1.,Recent models on bet-hedging germination in annual plants assume a negative relationship between the proportion of offspring that germinate and the quality of the maternal environment. An increase in the proportion of seeds remaining dormant in the next year, when produced in seasons with high reproduction may result from selection that avoids overcrowding in the following year. 2.,We present the first empirical test of this prediction by utilizing a field experiment in Israel which manipulated the entire maternal environment. We subjected semi-arid and Mediterranean annual plant communities to different rainfall treatments: control, reduced and increased rainfall. We then related maternal environment quality to offspring germination fractions for three focal species in two consecutive seasons. 3.,There was a negative relationship between the quality of the maternal environment and offspring germination fraction in four out of twelve cases. The negative relationship was stronger for the least competitive species and in the environment with high competition intensity, supporting the role of competition for the observed pattern. 4.,Our results suggest that competition with all neighbours is more likely to explain the pattern than sib competition. 5.,Synthesis. Our findings provide the first experimental evidence of a highly reliable cue (productivity of maternal environment) that allows for plants to respond to their future biotic environment. There is an urgent need for testing predictions of theoretical models in natural populations and for incorporating the role of density dependence in studies of bet-hedging germination. [source] Prejudicial Attitudes Toward Older Adults May Be Exaggerated When People Feel Vulnerable to Infectious Disease: Evidence and ImplicationsANALYSES OF SOCIAL ISSUES & PUBLIC POLICY, Issue 1 2009Lesley A. Duncan Prejudice against elderly people ("ageism") is an issue of increasing social concern, but the psychological roots of ageism are only partially understood. Recent theorizing suggests that ageism may result, in part, from fallible cue-based disease-avoidance mechanisms. The perception of subjectively atypical physical features (including features associated with aging) may implicitly activate aversive semantic concepts (implicit ageism), and this implicit ageism is likely to emerge among perceivers who are especially worried about the transmission of infectious diseases. We report an experiment (N = 88) that provides the first empirical test of this hypothesis. Results revealed that implicit ageism is predicted by the interactive effects of chronic perceptions of vulnerability to infectious disease and by the temporary salience of disease-causing pathogens. Moreover, these effects are moderated by perceivers' cultural background. Implications for public policy are discussed. [source] Growth responses of African savanna trees implicate atmospheric [CO2] as a driver of past and current changes in savanna tree coverAUSTRAL ECOLOGY, Issue 4 2010BARNEY S. KGOPE Abstract Atmospheric CO2 has more than doubled since the last glacial maximum (LGM) and could double again within this century, largely due to anthropogenic activity. It has been suggested that low [CO2] contributed to reduced tree cover in savanna and grassland biomes at LGM, and that increasing [CO2] over the last century promoted increases in woody plants in these ecosystems over the past few decades. Despite the implications of this idea for understanding global carbon cycle dynamics and key global role of the savanna biome, there are still very few experimental studies quantifying the effects of CO2 on tree growth and demography in savannas and grasslands. In this paper we present photosynthetic, growth and carbon allocation responses of African savanna trees (Acacia karroo and Acacia nilotica) and a C4 grass, Themeda triandra, exposed to a gradient of CO2 concentrations from 180 (typical of LGM) to 1000 µmol mol,1 in open-top chambers in a glasshouse as a first empirical test of this idea. Photosynthesis, total stem length, total stem diameter, shoot dry weight and root dry weight of the acacias increased significantly across the CO2 gradient, saturating at higher CO2 concentrations. After clipping to simulate fire, plants showed an even greater response in total stem length, total stem diameter and shoot dry weight, signalling the importance of re-sprouting following disturbances such as fire or herbivory in savanna systems. Root starch (per unit root mass and total root starch per plant) increased steeply along the CO2 gradient, explaining the re-sprouting response. In contrast to the strong response of tree seedlings to the CO2 gradient, grass productivity showed little variation, even at low CO2 concentrations. These results suggest that CO2 has significant direct effects on tree recruitment in grassy ecosystems, influencing the ability of trees to recover from fire damage and herbivory. Fire and herbivore regimes that were effective in controlling tree increases in grassy ecosystems could thus be much less effective in a CO2 -rich world, but field-based tests are needed to confirm this suggestion. [source] | ||||||||||