Learning from unrealized versus realized prices

Our market experiment investigates the extent to which traders learn from the price, differentiating between situations where orders are submitted before versus after the price has realized. When market participants have to submit their bids conditional on the price, they show a bias by reacting only to their private information and not to the hypothetical value of the price. In a sequential trading mechanism, where the price is known at the bid submission, bids react to price to an extent that is roughly consistent with the benchmark theory

Learning From Unrealized versus Realized Prices

Our experiments investigate the extent to which traders learn from the price, differentiating between situations where orders are submitted before versus after the price has realized. In simultaneous markets with bids that are conditional on the price, traders neglect the information conveyed by the hypothetical value of the price. In sequential markets where the price is known prior to the bid submission, traders react to price to an extent that is roughly consistent with the benchmark theory. The difference's robustness to a number of variations provides insights about the drivers of this effect

Decision-Making in Markets

Diese Dissertation erforscht, auf welchen unterschiedlichen Wegen Informationsverarbeitung Investitionsentscheidungen beeinflusst. Auf der Basis kontrollierter Laborexperimente wird untersucht, wie Entscheidungen mit der Art der Information sowie mit dem Entscheidungskontext variieren. Im ersten Kapitel legt ein Experiment die Schwierigkeit mit hypothetischem Denken bzw. mit dem Lernen aus hypothetischen Ereignissen offen. Im Kapitel Zwei untersucht ein anderes Experiment, wie Informationsverarbeitung die Reaktionen der Investoren auf Ambiguität verändert, denn ein eindeutiges, optimales Lernverhalten gibt es unter Ambiguität nicht. Das letzte Kapitel stellt anhand desselben Experiments die Unabhängigkeit zwischen dem Lernprozess und den Risikopräferenzen in Frage.This dissertation investigates various channels through which information processing affects investment decisions. Controlled laboratory experiments allow for studying how subjects’ decisions vary with the type of information and the decision-context. The experiment in the first chapter discloses the difficulty with contingent reasoning, i.e. learning from hypothetical events. A different experiment in Chapter Two analyzes how information processing changes investors’ reactions to ambiguity—an environment with multiple rational learning rules. Using the same experiment, the last chapter questions the independence between belief updating and risk preferences

Learning under Ambiguity: An Experiment in Gradual Information Processing

This experiment studies belief updating under ambiguity, using subjects' bid and ask prices for an asset with ambiguous payoff distribution. Bid and ask quotes allow for distinguishing between the two main paradigms of updating under ambiguity--full Bayesian updating and maximum likelihood updating. We find substantial heterogeneity in subjects' reaction to information. The majority of subjects (54\%) chose quotes that were in line with full Bayesian updating, while another, non-negligible, group (35\%) behaved like maximum likelihood updaters. (JEL: G11, C91, D81

The Resolution of Uncertainty in the Value and Probability Domains

We compare preferences for temporal resolution when uncertainty is resolved over a probability rather than a value. In various frameworks–e.g., Kreps and Porteus (1978)–, preferences over gradual versus one-shot resolution do not depend on whether values or probabilities define the main object of uncertainty. In our experiment, however, most subjects resolved uncertain values gradually but uncertain probabilities all at once–both in the gain and loss frames. This systematic discrepancy motivates an explanation for it that we call "process utility", which highlights the importance of information processing when deducing revealed preferences for temporal resolution from choice data

Antibacterial and antibiotic-potentiation activity of the constituents from aerial part of Donella welwitshii (Sapotaceae) against multidrug resistant phenotypes

Abstract Background The rise of multidrug-resistant (MDR) bacteria is a real public health problem worldwide and is responsible for the increase in hospital infections. Donella welwitschii is a liana or shrub belonging to the family Sapotaceae and traditionally used to cure coughs. Objective This study was conducted with the objective to validate the medicinal properties of this plant, the aerial part was studied for its phytochemical composition using column and PTLC chromatography and exploring its antibacterial and antibiotic-modifying activity as well as those of its phytochemicals. Methods The structures of the compounds were elucidated from their physical and spectroscopic data in conjunction with literature. The antibacterial activity of the isolated metabolites was performed toward a panel of MDR Gram negative and Gram-positive bacteria. The broth micro-dilution method was used to determine antibacterial activities, efflux pump effect using the efflux pump inhibitor (EPI) (phenylalanine-arginine-ß-naphthylamide (PAβN)), as well as the modulating activity of antibiotics. Monitoring the acidification of the bacterial growth medium was used to study the effects of the samples on the bacterial proton-ATPase pumps and cellular ATP production. Results Eleven compounds were isolated including pentacyclic triterpenes, C-glucosyl benzophenones. With a MIC value < 10 μg/mL, diospyric acid (7) significantly inhibited the growth of Escherichia coli AG102, Enterobacter aerogenes ATCC13048, Klebsiella pneumoniae KP55, Providencia stuartii NEA16 and Staphylococcus aureus MRSA3. 28-hydroxy-β-amyrin (8) significantly impaired the growth of Enterobacter aerogenes EA27, Klebsiella pneumoniae ATCC11296 and Staphylococcus aureus MRSA6; and oleanolic acid (9) strongly impaired the growth of Escherichia coli AG 102, Enterobacter aerogenes EA27 and Providencia stuartii PS2636. Diospyric acid (7) and 28-hydroxy-β-amyrin (8) induced perturbation of H+-ATPase pump and inhibition of the cellular ATP production. Moreover, at MIC/2 and MIC/4, compounds 7, 8, and 9 strongly improved the antibacterial activity of norfloxacin, ciprofloxacin and doxycycline with antibiotic-modulating factors ranging between 2 and 64. Conclusion The overall results of the current work demonstrate that diospyric acid (7), 28-hydroxy-β-amyrin (8) and oleanolic acid (9) are the major bioactive constituents of Donella welwitschia towards Gram-negative bacteria expressing MDR phenotypes