The 2014 International Planning Competition: Progress and Trends

We review the 2014 International Planning Competition (IPC-2014), the eighth in a series of competitions starting in 1998. IPC-2014 was held in three separate parts to assess state-of-the-art in three prominent areas of planning research: the deterministic (classical) part (IPCD), the learning part (IPCL), and the probabilistic part (IPPC). Each part evaluated planning systems in ways that pushed the edge of existing planner performance by introducing new challenges, novel tasks, or both. The competition surpassed again the number of competitors than its predecessor, highlighting the competition’s central role in shaping the landscape of ongoing developments in evaluating planning systems

Biases in human behavior

The paper shows that biases in individual’s decision-making may result from the process of mental editing by which subjects produce a “representation” of the decision problem. During this process, individuals make systematic use of default classifications in order to reduce the short-term memory load and the complexity of symbolic manipulation. The result is the construction of an imperfect mental representation of the problem that nevertheless has the advantage of being simple, and yielding “satisficing” decisions. The imperfection origins in a trade-off that exists between the simplicity of representation of a strategy and his efficiency. To obtain simplicity, the strategy’s rules have to be memorized and represented with some degree of abstraction, that allow to drastically reduce their number. Raising the level of abstraction with which a strategy’s rule is represented, means to extend the domain of validity of the rule beyond the field in which the rule has been experimented, and may therefore induce to include unintentionally domains in which the rule is inefficient. Therefore the rise of errors in the mental representation of a problem may be the "natural" effect of the categorization and the identification of the building blocks of a strategy. The biases may be persistent and give rise to lock-in effect, in which individuals remain trapped in sub-optimal strategies, as it is proved by experimental results on stability of sub-optimal strategies in games like Target The Two. To understand why sub-optimal strategies, that embody errors, are locally stable, i.e. cannot be improved by small changes in the rules, it is considered Kauffman’ NK model, because, among other properties, it shows that if there are interdependencies among the rules of a system, than the system admits many sub-optimal solutions that are locally stable, i.e. cannot be improved by simple mutations. But the fitness function in NK model is a random one, while in our context it is more reasonable to define the fitness of a strategy as efficiency of the program. If we introduce this kind of fitness, then the stability properties of the NK model do not hold any longer: the paper shows that while the elementary statements of a strategy are interdependent, it is possible to achieve an optimal configuration of the strategy via mutations and in consequence the sub-optimal solutions are not locally stable under mutations. The paper therefore provides a different explanation of the existence and stability of suboptimal strategies, based on the difficulty to redefine the sub-problems that constitute the building blocks of the problem’s representation

Testing systems of identical components

We consider the problem of testing sequentially the components of a multi-component reliability system in order to figure out the state of the system via costly tests. In particular, systems with identical components are considered. The notion of lexicographically large binary decision trees is introduced and a heuristic algorithm based on that notion is proposed. The performance of the heuristic algorithm is demonstrated by computational results, for various classes of functions. In particular, in all 200 random cases where the underlying function is a threshold function, the proposed heuristic produces optimal solutions

Success from Satisficing and Imitation: Entrepreneurs’ Location Choice and Implications of Heuristics for Local Economic Development

Decisions about location choice provide an opportunity to compare the predictions of optimization models, which require exhaustive search through very large choice sets, against the actual decision processes used by entrepreneurs choosing where to allocate investment capital. This paper presents new data on entrepreneurs’ self-described decision processes when choosing where to locate, based on scripted interviews with 49 well-placed business owners and senior managers in charge of location choice. Consideration sets are surprisingly small, especially among those who are successful. According to entrepreneurs’ own accounts, locations are frequently discovered by chance rather than systematic search. Few describe decision processes that bear any resemblance to equating marginal benefit with marginal cost as prescribed by standard optimization theory. Nearly all interviewees describe location choice decisions based on threshold conditions, providing direct evidence of satisficing rather than optimization. Imitation is beneficial for small investment projects. Decision process data collected here suggests a need to rethink standard policy tools used to stimulate local economic development.Process Model, Bounded Rationality, Interview Data, Ethnic, Discrimination, Low income, Neighborhood, Lexicographic, Non-compensatory, Business Owners

On the Significance of Information

Diese Dissertation unterstreicht die Rolle von Informationen bei der Erforschung ökonomischer Entscheidungen. Das erste Kapitel beschäftigt sich mit dem Zugang zu akkuraten Informationen über die Wirksamkeit medizinischer Interventionen. Unserem Model zufolge besteht in vielen entwickelten Ländern Nachfrage für Zugang zu unabhängigen medizinischen Informationen wie Cochrane Reviews. Wir schätzen, dass für viele Länder diese Nachfrage zu moderaten oder geringen Kosten erfüllt werden kann. Das zweite Kapitel beschäftigt sich mit der Kommunikation solcher Informationen und untersucht den unterstützenden Effekt natürlicher Häufigkeiten bei der Berechnung von A-posteriori Wahrscheinlichkeiten (Gigerenzer & Hoffrage, 1995). Durch eine Meta-Analyse erklären wir Konzepte und entflechten die Effekte von 15 Studienmerkmalen. Im einfachsten Studiendesign führen natürliche Häufigkeiten zu 24 Prozent korrekten Antworten verglichen mit 4 Prozent bei konditionellen Wahrscheinlichkeiten. Die finalen beiden Kapitel analysieren Satisficing-Strategien für unsichere Entscheidungsumgebungen in denen Agenten eine vollumfassende, probabilistische Beschreibung des Entscheidungsproblems fehlt. Simon (1955) zufolge nutzen Satisficing-Strategien ein Anspruchsniveau um die Suche nach weiteren Entscheidungsalternativen zu beenden. Das dritte Kapitel beschreibt wie solche Strategien in der ökonomischen Literatur als Präferenz modelliert werden um Entscheidungen zu erklären die der Nutzenmaximierung unterlegen sind während die Kognitionswissenschaften diese Strategien als Lösungen für Inferenzprobleme betrachten. Wir erklären die Divergenz mit unterschiedlichen Annahmen über die vorliegenden Informationen der Agenten. Das letzte Kapitel untersucht Satisficing-Strategien unter Taxifahrern. Wir stellen fest, dass die Stundenlöhne von Taxifahrern kaum vorhersagbar sind und ihre Entscheidungen Schichten zu beenden am besten durch einfache Satisficing-Strategien vorhergesagt werden können.This doctoral thesis emphasizes the significance of informational conditions in studying economic decisions. The first chapter concerns access to accurate probabilistic information in the domain of medical interventions. We estimate that, in many developed countries, there appears to be demand for governments to grant citizens free access to impartial reviews of medical evidence, as provided in Cochrane Reviews. For these countries, we estimate that this demand can be met at low costs. The second chapter concerns the communication of such information and examines the facilitating effect of natural frequencies on the derivation of posterior probabilities, as delineated by Gigerenzer and Hoffrage (1995). In a meta-analysis, we clarify concepts and disentangle the effects of 15 study characteristics. We find that in the simplest study design, 4 percent correct solutions when presented with conditional probabilities and 24 percent when presented with natural frequencies. The final two chapters examine the satisficing class of strategies for uncertain decision environments in which agents lack a full probabilistic description of the decision problem. According to Simon (1955), satisficing strategies use aspiration levels to terminate search for suitable alternatives. The third chapter describes how in economics, satisficing is modeled as a preference structure or as a decision rule that yields choices inferior to utility maximization, whereas in cognitive science, satisficing strategies use aspiration levels to solve inference problems. We explain the divergence, noting that they refer to risky and uncertain environments, respectively. The final chapter examines satisficing in an applied setting, studying taxi drivers' shift termination behavior. We find that drivers' hourly earnings are very uncertain and drivers’ behavior is best predicted by simple satisficing strategies that terminate shifts when reaching an aspired shift income or shift duration