Browsing by Subject "Experiment"

Now showing 1 - 7 of 7

Asymmetric obligations
(2011) Schildberg-Hörisch, Hannah; Riedel, Nadine
We use a laboratory experiment to investigate the behavioral effects of obligations that are not backed by binding deterrent incentives. To implement such expressive law' we introduce different levels of very weakly incentivized, symmetric and asymmetric minimum contribution levels (obligations) in a repeated public goods experiment. The results provide evidence for a weak expressive function of law: while the initial impact of high obligations on behavior is strong, it decreases over time. Asymmetric obligations are as effective as symmetric ones. Our results are compatible with the argument that expressive law affects behavior by attaching an emotional cost of disobeying the own obligation.
Contract design and insurance fraud : an experimental investigation
(2010) Schiller, Jörg; Lammers, Frauke
This paper investigates the impact of insurance contract design on the behavior of filing fraudulent claims in an experimental setup. We test how fraud behavior varies for insurance contracts with full coverage, a straight deductible or variable premiums (bonus-malus contract). In our experiment, filing fraudulent claims is a dominant strategy for selfish participants, with no psychological costs of committing fraud. While some people always commit fraud, a substantial share of people only occasionally or never defraud. In addition, we find that deductible contracts may be perceived as unfair and thus increase the extent of claim build-up compared to full coverage contracts. In contrast, bonus-malus contracts with variable insurance premiums significantly reduce the filing of fictitious claims compared to both full coverage and deductible contracts. This reduction cannot be explained by monetary incentives. Our results indicate that contract design significantly affects psychological costs and, consequently, the extent of fraudulent behavior of policyholders.
Flexible work arrangements and precautionary behaviour : theory and experimental evidence
(2020) Rostam-Afschar, Davud; Orland, Andreas
In the past years, work time in many industries has become increasingly flexible opening up a new channel for intertemporal substitution. To study this, we set up a two-period model with wage uncertainty. This extends the standard saving model by allowing a worker to allocate a fixed time budget between two work shifts or to save. To test the existence of these channels, we conduct laboratory consumption/saving experiments. A novel feature of our experiments is that we tie them to a real-effort style task. In four treatments, we turn on and off the two channels for consumption smoothing: saving and time allocation. Our four main findings are: (i) subjects exercise more effort under certainty than under risk; (ii) savings are strictly positive for at least 85 percent of subjects (iii) a majority of subjects uses time allocation to smooth consumption; (iv) saving and time shifting are substitutes, though not perfect substitutes.
Holzanatomische Veränderungen als Reaktion auf extreme Umweltereignisse in rezenten und subfossilen Eichen und deren Verifizierung im Experiment
(2014) Land, Alexander; Küppers, Manfred
This study focuses on changes in wood anatomy of recent (living study), container-grown (verification phase) and subfossil (subfossil study) oaks responding to severe biotic and abiotic events, as well as on “classical” tree-ring analysis (e.g. climate-growth relationships, signature-year analysis and age-trend analysis). Further, non-typical cell formations in wood anatomy with respect to the number, the shape and the size of xylem cells have been investigated. At this juncture, it was distinguished between continuous proxies (year-to-year), like total ring width or earlywood-vessel size, and non-continuous proxies (not year-to-year), like collapsed earlywood vessels or highly enhanced latewoodcell diameters. Measurement of annually resolved cross-section areas of earlywood vessels in recent and subfossil oak trees has been carried out by a specific developed semi-automatic tree ring image-analysis software (TRIAS). Basic objectives of this study were to connect the affecting biotic or abiotic events to specific changes in wood anatomy. Investigations on living (from locations with different side conditions in southern Germany) and container-grown (in the botanical garden, University of Hohenheim) oaks were performed to validate (verification phase) the results independently between the living and container study, getting clearer insights into the wood anatomical reaction of oaks and the homogeneity of the signal. Finally, the potential of qualitative and quantitative wood-anatomy for palaeo-climatology/-ecology is shown by applying the results to subfossil oaks (Holocene Oak Chronology Hohenheim). An event analysis was performed within two long-lasting periods (130 years and 1.000 years) in the mid-Holocene. Frequency distribution of extreme events, like high-magnitude floods or severe late-frost events, within these two periods in the mid-Holocene was compared with frequencies during the past 100 years. One result of this study is that one signature wood-anatomical change could be related to an extreme biotic or abiotic event, if the wood-anatomical feature occurred not only on local side level but on regional or national scale. Key evidence could be found for, that 1. out-of-true and collapsed earlywood vessels combined with traumatic tissue (wood-anatomical feature F/T) occurred after very low temperatures at the time of bud break, 2. intra-annual density bands are developed after rapid drops of temperature at an early stage (feature C) of the vegetation period or within (feature D) (depending on the position within the tree ring), 3. a long-lasting summer-flood event results in highly enhanced latewood-cell diameters (feature G), 4. a long-lasting spring-flood event reduces significantly the cross-section area of all vessels within earlywood (feature SEV), 5. latewood formation is absence or highly reduced in years with severe drought periods, 6. rapid drops of temperatures among winter periods (winter frost-events) reduce cross-section areas of initially built earlywood vessels (MVA5) and 7. continuous tree-ring proxies, like total ring width or earlywood-vessel variables, are significantly influenced by different climate factors. Wood-anatomical features from the recent study for 1., 3. and 4. could also be validated in the verification phase. The link between a biotic or abiotic event and the related specific wood-anatomical feature for 2., 5. and 6. could be found either in the recent study or the verification phase. Conducted measurements of diametrical stem growth, stem-growth dynamic and water deficit demonstrate big differences between the simulations (drought, frost, water logging, defoliation) that have been carried out on container-grown oaks. The simulations show massive changes in stem-growth dynamics of container-grown oaks affected by drought, frost and defoliation, whereas the waterlogged and control oaks reacted quite similar in their behaviour, and document the good adaptation of pedunculate oak trees to flooding. Pointer years were calculated and analysed for latewood and earlywood growth at the region Main and upper Rhine. Negative latewood-pointer years show great concurrence to years of annual summer-drought periods respectively long-lasting perennial droughts. Extreme events have been dated and analysed within two mid-Holocene periods of 2527-2396 BC (upper Rhine region) and 3279-2201 BC (Main region). High-magnitude floods and winter-frost events were dated using wood-anatomical features in subfossil oak trees (HOC Hohenheim). A “period of high river dynamic” in the Main valley could be analysed around 2750 BC. This result points out that the number of flood events in this period could be much higher than in the twentieth century whereas the number of detected winter-frost events at the upper Rhine region seems not to be increased compared to the past one hundred years.
The need to decipher plant drought stress along the soil-plant-atmosphere continuum
(2023) Schweiger, Andreas H.; Zimmermann, Telse; Poll, Christian; Marhan, Sven; Leyrer, Vinzent; Berauer, Bernd J.
Lacking comparability among rainfall manipulation studies is still a major limiting factor for generalizations in ecological climate change impact research. A common framework for studying ecological drought effects is urgently needed to foster advances in ecological understanding the effects of drought. In this study, we argue, that the soil–plant–atmosphere‐continuum (SPAC), describing the flow of water from the soil through the plant to the atmosphere, can serve as a holistic concept of drought in rainfall manipulation experiments which allows for the reconciliation experimental drought ecology. Using experimental data, we show that investigations of leaf water potential in combination with edaphic and atmospheric drought – as the three main components of the SPAC – are key to understand the effect of drought on plants. Based on a systematic literature survey, we show that especially plant and atmospheric based drought quantifications are strongly underrepresented and integrative assessments of all three components are almost absent in current experimental literature. Based on our observations we argue, that studying dynamics of plant water status in the framework of the SPAC can foster comparability of different studies conducted in different ecosystems and with different plant species and can facilitate extrapolation to other systems, species or future climates.
News endorser influence in social media
(2020) Teutsch, Doris; Trepte, Sabine
Social networking sites have become an online realm where users are exposed to news about current affairs. People mainly encounter news incidentally because they are re-distributed by users whom they befriended or follow on social media platforms. In my dissertation project, I draw on shared reality theory in order to examine the question of how the relationship to the news endorser, the person who shares news content, determines social influence on opinion formation about shared news. The shared reality theory posits that people strive to achieve socially shared beliefs about any object and topic because of the fundamental epistemic need to establish what is real. Social verification of beliefs in interpersonal communication renders uncertain and ambiguous individual perceptions as valid and objectively true. However, reliable social verification may be provided only by others who are regarded as epistemic authority, in other words as someone whose judgment one can trust. People assign epistemic authority particularly to socially close others, such as friends and family, or to members of their in-group. I inferred from this that people should be influenced by the view of a socially close news endorser when forming an opinion about shared news content but not by the view of a socially distant news endorser. In Study 1, a laboratory experiment (N = 226), I manipulated a female news endorser’s social closeness by presenting her as an in-group or out-group member. Participants’ opinion and memory of a news article were not affected by the news endorser’s opinion in either of the conditions. I concluded that the news article did not elicit motivation to strive for shared reality because participants were confident about their own judgment. Therefore, they did not rely on the news endorser’s view when forming an opinion about the news topic. Moreover, the results revealed that participants had stronger trust in the news endorser when she expressed a positive (vs. negative) opinion about the news topic, while social closeness to the news endorser did not predict trust. On the one hand, this is in line with the social norm of sharing positive thoughts and experiences on social networking sites: adherence to the positivity norm results in more favorable social ratings. On the other hand, my findings indicate that participants generally had a positive opinion about the topic of the stimulus article and thus had more trust in news endorsers who expressed a similar opinion. In Study 2, an online experiment (N = 1, 116), I exposed participants to a news post by a relational close vs. relational distant news endorser by having them name a close or distant actual Facebook friend. There was a small influence of the news endorser’s opinion on participants’ thought and opinion valence irrespective of whether the news endorser was a close or distant friend. The finding was surprising, particularly because participants reported stronger trust in the view of the close friend than in the view of a distant friend. I concluded that in light of an ambiguity eliciting news article, people may even rely on the views of less trustworthy news endorsers in order to establish a socially shared and, therefore, valid opinion about a news topic. Drawing on shared reality theory, I hypothesized that social influence on opinion formation is mediated by news endorser congruent responses to a news post. The results indicated a tendency for the proposed indirect relation however, the effect size was small and the sample in Study 2 was not large enough to provide the necessary statistical power to detect the mediation. In conclusion, the results of my empirical studies provide first insights regarding the conditions under which a single news endorser influences opinion formation about news shared on social networking sites. I found limited support for shared reality creation as underlying mechanism of such social influence. Thus, my work contributes to the understanding of social influence on news perception happening in social networking sites and proposes theoretical refinements to shared reality theory. I suggest that future research should focus on the role of social and affiliative motivation for social influences on opinion formation about news shared on social networking sites.
Der Sleeper Effekt : Theoriekritik und der Versuch eines Nachweises
(2018) Lindemann, Ann-Kathrin; Scheufele, Bertram
The sleeper effect was first described by Hovland, Lumsdaine and Sheffield (1949) in the 1940s. In the study, the influence of a propaganda movie on the attitudes of American soldiers seemed to grow over time: five days after watching the movie, the soldiers were less likely to agree with the movies conclusions than nine weeks later, when they showed a significant attitude change in line with the movies narrative. Consequently, the sleeper effect was defined as a persuasive media effect gaining strength with the passage of time. Despite its long research history, the origin of the sleeper effect is still undetermined (Kumkale & Albarracín, 2004). Therefore, one of the main objectives of this study is an in-depth review of the existing research literature regarding the underlying mechanisms which might cause the effect. Once these basic mechanisms are identified, the second objective is to test these principles in an experimental setting. The present study shows, that neither the order of presentation of the experimental stimuli, nor the extent of pre-existing attitudes have any influence on the sleeper effect - first and foremost, because the sleeper effect failed to occur in this experiment. Therefore, the question on how the sleeper effect is formed remains unsolved.