A simulation study on two analytical techniques for alternating treatments designs

Alternating treatments designs (ATDs) are single-case experimental designs entailing the rapid alternation of conditions, and the specific sequence of conditions is usually determined at random. The visual analysis of ATD data entails comparing the data paths formed by connecting the measurements from the same condition. Apart from visual analyses, there are at least two quantitative analytical options also comparing data paths. On option is a visual structured criterion (VSC) regarding the number of comparisons for which one conditions has to be superior to the other to consider that the difference is not only due to random fluctuations. Another option, denoted as ALIV (a comparison involving Actual and Linearly Interpolated Values), computes the mean difference between the data paths and uses a randomization test to obtain a p value. In the current study, these two options are compared, along with a binomial test, in the context of simulated data, representing ATDs with a maximum of two consecutive administrations of the same condition and a randomized block design. Both VSC and ALIV control Type I error rates, although these are closer to the nominal 5% for ALIV. In contrast, the binomial test is excessively liberal. In terms of statistical power, ALIV plus a randomization test is superior to VSC. We recommend that applied researchers complement visual analysis with the quantification of the mean difference, as per ALIV, and with a p value whenever the alternation sequence was determined at random. We have extended an already existing website providing the graphical representation and the numerical results

Four Contributions to Experimental Economics

In the following four chapters, distinct but related experimental research analyzing strategic and non-strategic economic behavior is presented. Chapter 2, entitled "Cooperation in Symmetric and Asymmetric Prisoner's Dilemma Games" is a systematic study of behavior in symmetric and asymmetric prisoner's dilemma games. The prisoner's dilemma is one of the key models in many disciplines for now over five decades. Previous prisoner's dilemma experiments show that in contrast to theoretical predictions, cooperation rates are generally very high in the symmetric payoff variant of the game. Chapter 2 studies cooperation in the prisoner's dilemma in a more realistic scenario by systematically analyzing the effects of asymmetric payoffs. Already in the early nineties Murnighan et al. (1990) noted that "research has been inexplicably absent on the effects of asymmetry". The present study takes this concern into account and focuses on this much broader type of conflict expanding the limited and rather unsystematic research conducted in this area. It analyzes and discusses the effect of asymmetry on cooperation in a 40 period prisoner's dilemma game in fixed partner design. A distinction is made between a high and low payoff symmetric prisoner's dilemma on the one hand and an asymmetric game combined out of both symmetric ones on the other hand. Asymmetry significantly decreases cooperation, as low-type players are more likely to defect after mutual cooperation while high-type players initiate cooperation more often than the former. Asymmetry also has a significant negative effect on the stability of cooperation rendering long sequences of mutual cooperation extremely rare. These results are not only a valuable addition to the existing (mostly symmetric) prisoner's dilemma literature but are also of relevance for understanding reciprocity, equity and fairness especially in light of recent theoretical developments based exclusively on symmetric experimental games. Chapter 3, entitled "Assignment versus Choice in Prisoner's Dilemma Experiments'' compares behavior in a repeated prisoner's dilemma game when players can choose between two different representations of the same prisoner's dilemma, to behavior when players are assigned to play a specific game. The chapter is concerned with the methodological question of the external validity of experimental research based on the assignment of participants to experimental games or decision situations. Experimental findings may systematically misrepresent field outcomes if assigning participants to experiments has an impact on the decisions made by the participants in the experiment and if such an assignment does not occur in the field. The chapter therefore analyzes to what extent experimental deviations from actual situations due to the assignment of participants is based exclusively on the possibility of self-selection or sorting, or whether choice has an important behavioral effect in itself. The chapter extends the results obtained in the experimental psychology literature by analyzing whether choice effects are also found in strategic contexts, rendering them of particular interest to economic environments. Based on the idea that choice either via active modification of the strategic environment or by passive self-selection into a particular strategic environment may be an important property of many empirical problems studied using experimental methods, the research goal is to separate a choice effect from sorting or self-selection effects. The experimental results clearly indicate that the mere fact that participants can choose the game they want to play has a statistically significant impact on behavior. Cooperation rates are up to 60% higher in the games that were not assigned to but chosen by participants. These findings are consistent with the robust evidence of the psychology literature on non-strategic contexts that choice increases motivation, trust, and performance. Given that in many contexts agents choose the strategic situation they get involved in, assigning participants to experiments may affect the external validity of some experimental findings. Chapter 4, entitled "The Role of Rivalry - Public Goods versus Common-Pool Resources" moves from the 2 person prisoner's dilemma game structure to the analysis of behavior in a 4 person quadratic public good and a quadratic common-pool resource game. Despite a large theoretical and empirical literature on public goods and common-pool resources, a systematic comparison of these two types of social dilemmas is lacking. In fact, there is some confusion about these two types of dilemma situations. As a result, they are often treated alike. An explicit example of this is provided by Gintis (2000) who argues that while "common pool resource and public goods games are equivalent for Homo Oeconomicus, people treat them quite differently in practice. This is because the status quo in the public goods game is the individual keeping all the money in the private account, while the status quo in the common pool resource game is that the resource is not being used at all." In line with the theoretical literature, the chapter first establishes theoretically that public good and common-pool resource games as used in the experimental literature are two distinct types of social dilemmas, the fundamental difference between the two games being the degree of rivalry. It is shown that the distinguishing feature of these two types of games lies in the distributional factor that determines whether the good is rival or non-rival. This difference gives rise to two distinct strategic environments. Based on these theoretical differences an experiment is devised that tests whether the theoretical differences have an impact on behavior. The results show that participants clearly respond to the differences in rivalry. Aggregate behavior in both games starts relatively close to Pareto efficiency and converges quickly to the respective Nash equilibrium. This clearly indicates that the differences in rivalry affect behavior, strengthening the importance of differentiating between the two types of games. Despite this difference reflecting the structure of the two games, there appear to be some behavioral similarities. In both games, aggregate behavior starts in the neighborhood of the Pareto optimum and moves rather quickly to the respective aggregate Nash equilibrium. Chapter 5 entitled "Purchase Decisions with Non-linear Pricing Options under Risk" moves away from a strategic game setting to an analysis of decisions under risk. The chapter reports on an experimental investigation of purchase decisions with linear and non-linear pricing under risk. Standard economic theory suggests that customers should be indifferent to the format of a price reduction. In particular this implies that one would expect a customer to switch from one pricing scheme to another (one supplier to another) as long as there is at least an expected reduction in the effective purchase price. The recent surge in the use of rebates, discounts, bonus and point schemes implemented by retailers but also observed in other levels of the production chain begs the question of whether traditional economic explanations do fully account for the increased usage of non-linear pricing methods. An understanding of potential behavioral reasons for using such pricing schemes - as presented in this chapter - may not only be relevant for their design, but also for wider policy considerations. The experiment presented is based on a single period stochastic inventory problem with endogenous cost. It extends classic binary lottery experiments to test standard decision theoretic predictions concerning purchasing behavior in a rebate and a discount scheme. The question to what extent customers continue to purchase under two mathematically isomorph formats of non-linear schemes even if switching to a linear pricing scheme is optimal is investigated. The results indicate that rebate and discount schemes exert a statistically significant attraction on customers. Given the increased role of non-linear pricing schemes, systematic deviations from optimal behavior are an important element in the design of such schemes and may raise consumer protection and competition policy issues. The chapter concludes with a discussion on how the results can be explained by decision heuristics.</p

Investigating Properties of Phonotactic Knowledge Through Web-Based Experimentation

The goal of this dissertation is to advance the state of the art of research in constraint-based phonotactics. It takes a two-pronged approach: a technological contribution intended to facilitate future research, and experiments which seek to shed light on high-level questions about the properties of phonotactic models that can guide the development of theoretical work. The technological contribution is a software package called Speriment which allows experimenters to create and run experiments over the internet without advanced programming techniques. This software is particularly well suited to the kinds of experiments often run in phonotactic research, but can also be used for experiments in other domains of linguistics and the social sciences. It is hoped that this software will make it faster and easier to conduct phonotactic and other experiments as well as encourage experimenters to increase the reproducibility and transparency of their research. The experiments presented here address questions that assume constraint-based phonotactic frameworks, but that do not rely on particular theories of the content of the constraint set. That is, they apply to constraint-based frameworks for theories of phonotactics, with the first study seeking to distinguish between two such frameworks, a linear version of Harmonic Grammar and Maximum Entropy, while the second investigates whether phonotactic knowledge is independent of knowledge of phonological alternations. These coarse-grained questions about phonotactic knowledge on how pieces of phonotactic knowledge interact with each other and with another part of the grammar are intended to add to the groundwork on which phonotactic models and models of all phonological knowledge are built. Their findings have implications for which constraint-based frameworks should be used for future theories and how these theories can be reliably tested

Using a visual structured criterion for the analysis of alternating-treatment designs

Although visual inspection remains common in the analysis of single-case designs, the lack of agreement between raters is an issue that may seriously compromise its validity. Thus, the purpose of our study was to develop and examine the properties of a simple structured criterion to supplement the visual analysis of alternating-treatment designs. To this end, we generated simulated datasets with varying number of points, number of conditions, effect sizes and autocorrelations, and then measured Type I error rates and power produced by the visual structured criterion (VSC) and permutation analyses. We also validated the results for Type I error rates using nonsimulated data. Overall, our results indicate that using the VSC as a supplement for the analysis of systematically alternating-treatment designs with at least five points per condition generally provides adequate control over Type I error rates and sufficient power to detect most behavior changes

Analyzing data from single-case alternating treatments designs

Alternating treatments designs (ATDs) have received comparatively less attention than other single-case experimental designs in terms of data analysis, as most analytical proposals and illustrations have been made in the context of designs including phases with several consecutive measurements in the same condition. One of the specific features of ATDs is the rapid (and usually randomly determined) alternation of conditions, which requires adapting the analytical techniques. First, we review the methodologically desirable features of ATDs, as well as the characteristics of the published single-case research using an ATD, which are relevant for data analysis. Second, we review several existing options for ATD data analysis. Third, we propose 2 new procedures, suggested as alternatives improving some of the limitations of extant analytical techniques. Fourth, we illustrate the application of existing techniques and the new proposals in order to discuss their differences and similarities. We advocate for the use of the new proposals in ATDs, because they entail meaningful comparisons between the conditions without assumptions about the design or the data pattern. We provide R code for all computations and for the graphical representation of the comparisons involved. (PsycINFO Database Record

The interaction between the proliferating macroalga Asparagopsis taxiformis and the coral Astroides calycularis induces changes in microbiome and metabolomic fingerprints

Mediterranean Sea ecosystems are considered as hotspots of biological introductions, exposed to possible negative effects of non-indigenous species. In such temperate marine ecosystems, macroalgae may be dominant, with a great percentage of their diversity represented by introduced species. Their interaction with temperate indigenous benthic organisms have been poorly investigated. To provide new insights, we performed an experimental study on the interaction between the introduced proliferative red alga Asparagopsis taxiformis and the indigenous Mediterranean coral Astroides calycularis. The biological response measurements included meta-barcoding of the associated microbial communities and metabolomic fingerprinting of both species. Significant changes were detected among both associated microbial communities, the interspecific differences decreasing with stronger host interaction. No short term effects of the macroalga on the coral health, neither on its polyp activity or its metabolism, were detected. In contrast, the contact interaction with the coral induced a change in the macroalgal metabolomic fingerprint with a significant increase of its bioactivity against the marine bacteria Aliivibrio fischeri. This induction was related to the expression of bioactive metabolites located on the macroalgal surface, a phenomenon which might represent an immediate defensive response of the macroalga or an allelopathic offense against coral.ERA-NET Biome project "SEAPROLIF"; CNRS; Provence Alpes Cote d'Azur Region; TOTAL Fundation; Fundacao para a Ciencia e a Tecnologia (FCT) [Netbiome/0002/2011]; FCT fellowships [SFRH/BPD/63703/2009, SFRH/BPD/107878/2015]info:eu-repo/semantics/publishedVersio

A Priori Justification for Effect Measures in Single-Case Experimental Designs

Due to the complex nature of single-case experimental design data, numerous effect measures are available to quantify and evaluate the effectiveness of an intervention. An inappropriate choice of the effect measure can result in a misrepresentation of the intervention effectiveness and this can have far-reaching implications for theory, practice and policymaking. As guidelines for reporting appropriate justification for selecting an effect measure are missing, the first aim is to identify the relevant dimensions for effect measure selection and justification prior to data gathering. The second aim is to use these dimensions to construct a user-friendly flowchart or decision tree guiding applied researchers in this process. The use of the flowchart is illustrated in the context of a preregistered protocol. This study is the first study that attempts to propose reporting guidelines to justify the effect measure choice, before collecting the data, to avoid selective reporting of the largest quantifications of an effect. A proper justification, less prone to confirmation bias, and transparent and explicit reporting can enhance the credibility of the single-case design study findings

Investigation of charge migration/transfer in radical cations using Ehrenfest method with fully quantum nuclear motion

The main focus of this thesis is to investigate the effect of charge migration on molecular dynamics. Upon the creation of a superposition of cationic states by a short ionizing pulse in an attosecond pump-probe experiment, the electronic wavefunction is in a non-stationary state and the initial dynamics are purely electronic, driven by Charge Migration (CM) before the onset of any nuclear motions. The CM can be simulated using a frozen nuclear framework but its importance on long-term dynamics and competition with vibrationally mediated charge motion (i.e. Charge Transfer (CT)) remains unknown. Unravelling the mechanism behind CM and its importance on electron and nuclear coherence can help in designing an initial superposition of electronic states to steer nuclear motions toward a specific product. Further control of the photo-reactivity could be achieved with the use of probe/control laser pulses and open the door for more direct comparison with experimental results. In order to investigate the dynamics upon photoionization with an attosecond pump-pulse, the coupled electron-nuclear dynamics of the system is simulated using nonadiabatic quantum dynamics techniques within the sudden approximation. A single-set approach is adopted for the expansion of the nuclear wavefunction using a linear combination of Gaussian Wavepackets (GWP). The calculation is done using the Quantum-Ehrenfest method (QuEh) and the time-dependent Potential Energy Surfaces (PES) are evaluated with the Complete Active Space Configuration Interatcion (CAS-CI) method. The resulting dynamics are analyzed with adiabatic/diabatic state populations, Normal Mode (NM) displacements and bond lengths averaged over the nuclear wavepacket using Gross Gaussian populations (GGP). To reduce the cost of computation, the algorithm implemented in QUANTICS is parallelized with a Message Passing Interface (MPI). Further, the section of code which interacts with the database that contains previously calculated points on the PES is rewritten using the Structured Query Language (SQL) and the SQLite engine. For the purpose of unravelling the mechanism behind CM, the nonadiabatic dynamics of a model retinal Protonated Schiff Base (rPSB) and benzene are investigated by defining the initial electronic wavefunction in a systematic way. As demonstrated by the results on rPSB, the relaxation mechanism such as single and double bond length alternation and isomerization can controlled by varying the initial composition of electronic states. With the rich symmetry of benzene, the initial nuclear dynamics which are controlled by an initial gradient and electron dynamics can be analyzed using symmetry rules. The initial gradient is a combination of totally symmetric motion and non-symmetric components which correspond to the intra- (eigenstate) and inter-state (couplings) gradients, respectively. The electron dynamics and its associated nuclear motions can be examined by grouping together the localized holes where the CM occurs. With the initial gradient and CM, one can predict the initial nuclear relaxation and possibly control the photo-products formed by designing a specific superposition of electronic eigenstates. To explore the effect of laser pulses on dynamics, an implementation within the dipole approximation using the dipole-electric field dot product is done in the GAUSSIAN program. The dynamics in the presence of an infrared probe pulse is simulated on model systems such as allene and the ethylene cation. The pulse is able to induce change in the electron and nuclear dynamics of the system and some of its effect can be explained using irreducible representations and the alignment of the electric fields. The work presented in this thesis offers an insight into the photocontrol of molecules and opens the door for further investigation of charge-directed dynamics