The Signalling Power of Sanctions in Collective Action Problems

We present a model of collective action in a heterogenous population of egoists and conditional cooperators. Each player is uncertain about the cooperative inclinations of the other player. A government or principal who has information about the distribution of types may introduce sanctions for defection. We study the impact of such sanctions through the e¤ect on the beliefs of the players about the distribution of types they are facing. It is shown that in equilibrium sanctions can crowd out trust between agents by sending a signal that there are many egoists around. This can lead the government to set low sanctions to induce trust and 'crowd in' cooperation. In cases where conditional cooperation is an important factor in collective action, as is the case in tax compliance, the model provides a rationale for the low observed sanctions in the real world.Collective action, trust, incentives, crowding out, conditional cooperation

The birth process of periodic orbits in non-twist maps

We study the birth process of periodic orbits in non-twist systems, by means of a model map which contains all the typical features of such a system. The most common form of the birth process, or standard scenario, is described in detail. This scenario involves several steps: first one “dimerized” chain of saddle-center pairs is born, then a second, and eventually these two chains are reconnected into two Poincaré-Birkhoff chains.\ud \ud We also discuss several variations on this standard scenario. These variations can give rise to arbitrarily many chains, intertwined in a complex fashion, and the reconnection of these chains can be highly non-trivial.\ud Finally we study the effect of dissipation on the birth process. For sufficiently small dissipation one can still recognize the birth and reconnection processes, but with several new features. In the first place, the chains do not consist anymore of conservative saddles and centers, but rather of dissipative saddles and nodes. Furthermore, the dissipation destrtoys the symmetry between the inner and outer chains, and as a result the reconnection does not take place in one single step anymore, but in three

Status-Seeking in Criminal Subcultures and the Double Dividend of Zero-Tolerance

This paper offers a new argument for why a more aggressive enforcement of minor offenses ('zero-tolerance') may yield a double dividend in that it reduces both minor offenses and more severe crime. We develop a model of criminal subcultures in which people gain social status among their peers for being 'tough' by committing criminal acts. As zero-tolerance keeps relatively 'gutless' people from committing a minor offense, the signaling value of that action increases, which makes it attractive for some people who would otherwise commit more severe crime. If social status is sufficiently important in criminal subcultures, zero-tolerance reduces crime across the board.status concerns, street crime, subcultures, penalties, zero-tolerance, broken windows policing

Mode competition in a system of two parametrically driven pendulums: the role of symmetry

This paper is the final part in a series of four on the dynamics of two coupled, parametrically driven pendulums. In the previous three parts (Banning and van der Weele, Mode competition in a system of two parametrically driven pendulums; the Hamiltonian case, Physica A 220 (1995) 485¿533; Banning et al., Mode competition in a system of two parametrically driven pendulums; the dissipative case, Physica A 245 (1997) 11¿48; Banning et al., Mode competition in a system of two parametrically driven pendulums with nonlinear coupling, Physica A 245 (1997) 49¿98) we have given a detailed survey of the different oscillations in the system, with particular emphasis on mode interaction. In the present paper we use group theory to highlight the role of symmetry. It is shown how certain symmetries can obstruct period doubling and Hopf bifurcations; the associated routes to chaos cannot proceed until these symmetries have been broken. The symmetry approach also reveals the general mechanism of mode interaction and enables a useful comparison with other systems

Heroes of Agricultural Innovation

New technology has a prominent place in the theory and practice of innovation, but the association between high tech and innovation is not inevitable. In this paper, we discuss six metaphorical heroes of agricultural innovation, starting with the dominant hero of frontier science and technology. At first sight, our six heroes can be divided in those who are pro- and those who are anti-technology. Yet in the end technology, and more specifically GM technology, does not emerge as the main issue. Empowering the poor, finding solutions for urgent climate problems, and enhancing the quality of our daily relations to food and the environment – these are the issues the heroes are fighting for. Relations between innovation and (frontier) technology are better seen as a matter of pragmatic consideration, we will argue