Publications

Juvenile hormones (JHs) are key insect endocrine signals, regulating pre-adult development and adult life history strategies, physiology, and behavior. The importance of JHs for insects has led to the development of insecticides targeting JH signaling pathways. While effective against target pests, they can also affect beneficial insects, such as pollinators and natural pest enemies, many of which are Hymenopterans. In social Hymenoptera, JH-III plays key roles in regulating processes crucial for colony organisation and function. Emerging evidence of JH’s roles and its agrochemical disruption highlights the need for deeper research in non-target pests and particularly in beneficial insects such as key pollinator bees. Studying JH functions requires effective means to manipulate its circulating levels and signaling pathways. A common method for reducing JH titers includes applying the phytotoxin Precocene-I (P-I), which abolishes JH biosynthesis in the Corpora Allata (CA) glands. However, achieving consistently effective topical treatments has proven challenging. Here, we investigated the dynamics of the effect of P-I manipulations on JH titers and reproductive development in queenless worker groups of a key pollinator bumble bee. A single P-I treatment effectively reduced circulating JH levels in newly emerged workers, even after 12 days. The treatment delayed but did not prevent ovarian activation. Multiple treatments failed to further reduce JH titers or ovarian activity and were overall less effective than surgically removing the CA glands. Finally, we suggest guidelines for developing P-I manipulation studies relevant to insects, and more generally, compare methods for reducing circulating JH levels in insects.

Previous research has established that men are more likely to vote for populist radical right parties (PRRPs) than women. This article shows how cross-national and temporal variations in PRRPs’ electoral success interact with individuals’ risk propensity to affect this gender gap. We hypothesize that gender differences in the electoral support of PRRPs stem from disparities in risk-taking. We conceptualize risk in terms of two components, social and electoral, and demonstrate that women are more risk-averse regarding both. Our analysis is based on public opinion data from 14 countries (2002–2016) combined with macro-level data on PRRPs’ past parliamentary fortunes. To distinguish between the social and the electoral component in risk-taking, we use the illustrative case study of Germany. Findings demonstrate that gender differences in risk-taking and, by implication, the differences between women’s and men’s responses to the electoral context, are key to understanding the voting gender gap.

This paper characterizes the preferences over bounded infinite utility streams that satisfy the time value of money principle and an additivity property, and preferences that in addition are impatient. Based on this characterization, the paper introduces a concept of optimization that is robust to a small imprecision in the specification of the preference, and proves that the set of feasible streams of payoffs of a finite Markov decision process admits such a robust optimization.

Causative constructions come in lexical and periphrastic variants, exemplified in English by Sam killed Lee and Sam caused Lee to die. While use of the former, the lexical causative, entails the truth of the latter, an entailment in the other direction does not hold.  The source of this asymmetry is commonly ascribed to the lexical causative having an additional prerequisite of “direct causation", such that the causative relation holds between a contiguous cause and effect (Fodor 1970, Katz 1970).  However, this explanation encounters both empirical and theoretical problems (Nelleman & van der Koot  2012). To explain the source of the directness inferences (as well as other longstanding puzzles), we propose a formal analysis based on the framework of Structural Equation Models (SEMs) (Pearl 2000) which provides the necessary background for licensing causal inferences. Specifically, we provide a formalization of a 'sufficient set of conditions' within a model and demonstrate its role in the selectional parameters of causative descriptions. We argue that “causal sufficiency” is not a property of singular conditions, but rather sets of conditions, which are individually necessary but only sufficient when taken together (a view originally motivated in the philosophical literature by Mackie 1965). We further introduce the notion of a “completion event” of a sufficient set, which is critical to explain the particular inferential profile of lexical causatives. 

This paper introduces a systematic way of analyzing the semantics of causative linguistic expressions, and of how causal relations are expressed in natural languages. The starting point for this broad agenda is to provide an explanation for the asymmetrical inferential relationship between two causative constructions: change-of-state (CoS) verbs and the verb cause, commonly ascribed to the former having an additional prerequisite of direct causation. The direct causation hypothesis, however, is fraught with empirical and theoretical challenges. At the theoretical level, capturing the felicity conditions specific to CoS verbs and the notion of direct causation requires a means of modelling complex causal structures. This is on no account a trivial task, as it necessitates, inter alia, modelling causation in a way that is germane to the linguistic expressions designating such relations. Hence, the main objective of this paper is to develop a framework for modelling the  semantics of causal statements. For this purpose, this paper makes use of the framework
of Structural Equation Modelling (SEM), and it demonstrates how this approach provides tools for a rigorous model-theoretic treatment of the differential semantics of causal  expressions. This paper introduces formal logical definitions of different types of conditions  using SEM networks, and show how this proposal and the formal tools it employs allow us to make sense of the asymmetric entailment relationship between the two constructions. In our proposal, CoS verbs do not require contiguity between cause and effect at all, but instead they require that its subject is set by default to a participant in completion event, the event which “completes” a sufficient set of conditions, such that following this event (but not before) the values of the set of conditions in the sufficient set entail that the effect occurs. According to this, the intuition of direct causation arises (epiphenomenally) from contrasting CoS verbs with overt cause sentences: the stronger selection pattern of the former - which requires a completion event - may exclude more temporally distant conditions, while the latter admits any necessary condition. 

 An absorbing game is a two-person zero-sum repeated game. Some of the entries are ``absorbing'' in the sense that, following the play of an absorbing entry, with positive probability all future payoffs are equal to that entry's payoff. The outcome of the game is the long-run average payoff.
 We prove that a two-person zero-sum absorbing game, with either finite or compact action sets, has, for each e>0, e-optimal strategies with finite memory. In fact, we show that there is an e-optimal strategy that depends on the clock and three states of memory.