The experience is (not) everything: Sequential outcomes and social decision-making

In multiple pre-registered experiments, we examine the effect of sequences of positive and negative experiences on altruism, trust, trustworthiness, and cooperation. For non-social experiences, we find no effect on subsequent behavior in any of these social domains. However, when experiences are social in nature, we find more cooperation after gains than after losses. For neutral experiences with gains equalizing losses, we find no evidence for a differential effect of experiences irrespective of whether the experience is social or not. Our findings are in line with recent evidence on decision making under risk, showing that the effect of prior experiences depends on task similarity. Beyond that, we extend these findings to various forms of social decision making. Our results suggest that the overall valence of an experience (gain or loss) matters, whereas its dynamic trend (improving or deteriorating) does not

Imitation, network size, and efficiency

A number of theoretical results have provided sufficient conditions for the selection of payoff-efficient equilibria in games played on networks when agents imitate successful neighbors and make occasional mistakes (stochastic stability). However, those results only guarantee full convergence in the long-run, which might be too restrictive in reality. Here, we employ a more gradual approach relying on agent-based simulations avoiding the double limit underlying these analytical results. We focus on the circular-city model, for which a sufficient condition on the population size relative to the neighborhood size was identified by Alós-Ferrer & Weidenholzer [(2006) Economics Letters, 93, 163–168]. Using more than 100,000 agent-based simulations, we find that selection of the efficient equilibrium prevails also for a large set of parameters violating the previously identified condition. Interestingly, the extent to which efficiency obtains decreases gradually as one moves away from the boundary of this condition

Evolution, Bounded Rationality and Institutions

This dissertation consists of five self-contained research papers that cover theoretical work, simulation-based research, and experimental studies. My research interests are mainly focused on two interrelated areas within economics. One area is concerned with the economic consequences as well as the foundations of boundedly rational behavior. The other area is more specific and concerns the design of institutions and how they can be used to shape behavior and align incentives. The first chapter belongs to both areas, Chapters 2 and 3 cover topics from the former area, whereas the last two chapters contribute to the latter area. Chapter 1 concerns the role of trader matching with regard to the selection of market institutions by boundedly rational traders. Chapter 2 presents results on the stability of the Cournot-Nash and the Walrasian equilibrium under imitative behavior. Chapter 3 presents a model linking response times and iterative thinking and provides experimental evidence regarding the underlying processes of iterative thinking. Chapter 4 investigates the effects of a leniency mechanism on collusive bribery and tax evasion. Chapter 5 asks how the timing of punishment and the timing of the resolution of uncertainty affect deterrence of illicit behavior. In the remainder of this section I present a brief introduction for each chapter and summarize the main findings

The reinforcement paradox: monetary incentives and Bayesian updating

We report the results of two pre-registered experiments designed to study the reinforcement paradox: increased incentives often fail to increase and sometimes even decrease performance in Bayesian updating tasks. We argue that, in the presence of win/loss cues, higher incentives have two countervailing effects: increased error rates for reinforcement behavior (win-stay, lose-shift) and increased performance for decisions resulting from Bayesian updating. We find some evidence that incentives increase performance when the win/loss cue is removed whereas when reinforcement is active the effects of incentives are mixed

Spectroscopy of a fractional Josephson vortex molecule

In long Josephson junctions with multiple discontinuities of the Josephson phase, fractional vortex molecules are spontaneously formed. At each discontinuity point a fractional Josephson vortex carrying a magnetic flux $|\Phi|<\Phi_0$, $\Phi_0\approx 2.07\times 10^{-15}$ Wb being the magnetic flux quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency that depends on $\Phi/\Phi_0$ and lies inside the plasma gap. We experimentally investigate the dependence of the eigenfrequencies of a two-vortex molecule on the distance between the vortices, on their topological charge $\wp=2\pi\Phi/\Phi_0$ and on the bias current $\gamma$ applied to the Josephson junction. We find that with decreasing distance between vortices, a splitting of the eigenfrequencies occurs, that corresponds to the emergence of collective oscillatory modes of both vortices. We use a resonant microwave spectroscopy technique and find good agreement between experimental results and theoretical predictions.Comment: submitted to Phys. Rev.

Advances in ultra-high-pressure and multi-dimensional liquid chromatography instrumentation and workflows

The present contribution discusses recent advances in ultra-high-pressure liquid chromatography (UHPLC) and multi-dimensional liquid chromatography (MDLC) technology. First, new developments in UHPLC column technology and system design are highlighted. The latter includes a description of a novel injector concept enabling method speed-up, emerging detectors, and instrument diagnostics approaches. Next, online MDLC workflows are reviewed and advances in modulation technology are highlighted. Finally, key applications published in 2020 are reviewed

Simultaneous observation of high order multiple quantum coherences at ultralow magnetic fields

We present a method for the simultaneous observation of heteronuclear multi-quantum coherences (up to the 3rd order), which give an additional degree of freedom for ultralow magnetic field (ULF) MR experiments, where the chemical shift is negligible. The nonequilibrium spin state is generated by Signal Amplification By Reversible Exchange (SABRE) and detected at ULF with SQUID-based NMR. We compare the results obtained by the heteronuclei Correlated SpectroscopY (COSY) with a Flip Angle FOurier Series (FAFOS) method. COSY allows a quantitative analysis of homo- and heteronuclei quantum coherences

Spectroscopy of the fractional vortex eigenfrequency in a long Josephson 0-kappa junction

Fractional Josephson vortices carry a magnetic flux Phi, which is a fraction of the magnetic flux quantum Phi_0 ~ 2.07x10^{-15} Wb. Their properties are very different from the properties of the usual integer fluxons. In particular, fractional vortices are pinned and have an oscillation eigenfrequency which is expected to be within the Josephson plasma gap. Using microwave spectroscopy, we investigate the dependence of the eigenfrequency of a fractional Josephson vortex on its magnetic flux $\Phi$ and on the bias current. The experimental results are in good agreement with the theoretical predictions.Comment: submitted to PR

When are efficient conventions selected in networks?

We study the determinants of convergence to efficient conventions in coordination games played on networks, when agents focus on past performance (imitative play). Previous theoretical results provide an incomplete picture and suggest potentially-complex interactions between the features of dynamics and behavior. We conducted an extensive simulation study (with approximately 1.12 million simulations) varying network size, interaction and information radius, the probability of actual interaction, the probability of mistakes, tie-breaking rules, and the process governing revision opportunities. Our main result is that “more interactions,” be it in the form of larger interaction neighborhoods or of a higher interaction probability, lead to less coordination on efficient conventions. A second observation, confirming previous but partial theoretical results, is that a large network size relative to the size of neighborhoods (a “large world”) facilitates convergence to efficient conventions. Third, a larger information neighborhood helps efficiency because it increases visibility of efficient payoffs across the network. Last, technical details of the dynamic specification as tie-breaking or inertia, while often relevant for specific theoretical results, appear to be of little empirical relevance in the larger space of dynamics

Thermal escape of fractional vortices in long Josephson junctions

We consider a fractional Josephson vortex in a long 0-kappa Josephson junction. A uniformly applied bias current exerts a Lorentz force on the vortex. If the bias current exceeds the critical current, an integer fluxon is torn off the kappa-vortex and the junction switches to the voltage state. In the presence of thermal fluctuations the escape process takes place with finite probability already at subcritical values of the bias current. We experimentally investigate the thermally induced escape of a fractional vortex by high resolution measurements of the critical current as a function of the topological charge kappa of the vortex and compare the results to numerical simulations for finite junction lengths and to theoretical predictions for infinite junction lengths. To study the effect caused by the junction geometry we compare the vortex escape in annular and linear junctions.Comment: submitted to PR