Revisiting Strategic versus Non-strategic Cooperation

We use a novel experimental design to disentangle strategically- and non-strategically-motivated cooperation. By using contingent responses in a repeated sequential prisoners’ dilemma with a known probabilistic end, we differentiate end-game behavior from continuation behavior within individuals while controlling for expectations. This design allows us to determine the extent to which strategically-cooperating individuals are responsible for the so-called endgame effect. Experiments with two different subject pools indicate that the most common motive for cooperation in repeated games is strategic and that the extent to which endgame effects are driven by strategically-cooperating individuals depends on the profitability of cooperation.reputation building;strong reciprocity;conditional cooperation;strategic cooperation

Time Vs. Goods: The Value of Measuring Household Production Technologies

We take U.S. and Israeli household data on expenditures of time and goods, generate an exhaustive set of commodities that households produce/consume using them, and calculate their relative goods intensities. Leisure activities are uniformly relatively time intensive, health, travel and lodging relatively goods intensive. We demonstrate how education and age alter the goods intensity of household production. The results of this accounting can be used as guides to: Understanding how goods and income taxation interact to affect welfare; expanding notions of the determinants of international flows of goods; generating models of business cycles and endogenous growth to include interactions of goods and time consumption; and obtaining better measures of the distribution of well being.

A note on the food of Malabar travally, Carangoides malabaricus (Bloch & Schneider) from the north-western Bay of Bengal

Carangoides malabaricus(Bloch & Schneider) is the most important carangid landed by the trawlers operating in the north-western Bay of Bengal. It is observed in the trawl catches at all hours of the day. Preliminary observations on the food and feeding habits of the fish collected during 1964-66 show that it is essentially a carnivore and a column feeder and that Acetes, prawns, Squilla, crabs and miscellaneous small fishes are the important items of food besides small quantities of mysids, amphipods, other crustaceans, squids and cuttle fish

Conditional Cooperation: Disentangling Strategic from Non-Strategic Motivations

We use a novel experimental design to examine the role of reputational concerns in explaining conditional cooperation in social dilemmas. By using the strategy method in a repeated sequential prisoners’ dilemma in which the probabilistic end is known, we can distinguish between strategically and non-strategically motivated cooperation. Second movers who are strong reciprocators ought to conditionally cooperate with first movers irrespective of whether the game continues or not. In contrast, strategically motivated second movers conditionally cooperate only if the game continues and they otherwise defect. Experimental results, with two different subject pools, indicate reputation building is used around 30% of the time, which accounts for between 50% and 75% of all realized cooperative actions. The percentage of strong reciprocators varied between 6% to 23%.cooperation;reputation building;strong reciprocity;repeated prisoners’ dilemma

The Demand for Variety: A Household Production Perspective

Product diversity pervades every modern marketplace, and economists have devoted substantial attention to firms' decisions about the supply of variety. This study looks at the consumer's side by discussing the demand for variety. Using the framework of the home-production model, we trace differences in demand to differences in the opportunity costs of various activities. The cost differences are associated with investments in human capital; and the resulting differences in schooling attainment produce differences in time costs that in turn alter the kinds and variety of activities in which household members engage. Using time-budget surveys from Australia, Israel, the Netherlands, Sweden, the United States and West Germany from between 1985 and 1994, we find substantial differences among households in the extent of variety in the nonwork activities that they produce. More educated individuals generate more variety, engaging in both additional activities and the same ones as the less educated, with most of the effect of education on the variety of nonroutine activities. There is more variety on weekends; women engage in more different activities than men; young children add to variety in household consumption/production, especially among women; and income effects are clearly positive.

The demand for variety: a household production perspective

Economists have devoted substantial attention to firms’ supply of variety, but little to consumers' demand for variety. Employing the framework of home production, we trace differences in demand to differences in the opportunity costs of activities, which are associated with investments in human capital. Schooling alters time costs and changes the variety of activities household members choose. In time budgets from Australia, Israel, and West Germany we find that higher own and spouses' incomes raise variety (suggesting positive income effects). Education increases variety independent of income and earnings; part of its impact goes beyond a correlation of educational attainment with preferences for variety

Heralded phase-contrast imaging using an orbital angular momentum phase-filter

We utilise the position and orbital angular momentum (OAM) correlations between the signal and idler photons generated in the down-conversion process to obtain ghost images of a phase object. By using an OAM phase filter, which is non-local with respect to the object, the images exhibit isotropic edge-enhancement. This imaging technique is the first demonstration of a full-field, phase-contrast imaging system with non-local edge enhancement, and enables imaging of phase objects using significantly fewer photons than standard phase-contrast imaging techniques

Spreading dynamics on spatially constrained complex brain networks

The study of dynamical systems defined on complex networks provides a natural framework with which to investigate myriad features of neural dynamics and has been widely undertaken. Typically, however, networks employed in theoretical studies bear little relation to the spatial embedding or connectivity of the neural networks that they attempt to replicate. Here, we employ detailed neuroimaging data to define a network whose spatial embedding represents accurately the folded structure of the cortical surface of a rat brain and investigate the propagation of activity over this network under simple spreading and connectivity rules. By comparison with standard network models with the same coarse statistics, we show that the cortical geometry influences profoundly the speed of propagation of activation through the network. Our conclusions are of high relevance to the theoretical modelling of epileptic seizure events and indicate that such studies which omit physiological network structure risk simplifying the dynamics in a potentially significant way

Testing for entanglement with periodic coarse-graining

Continuous variables systems find valuable applications in quantum information processing. To deal with an infinite-dimensional Hilbert space, one in general has to handle large numbers of discretized measurements in tasks such as entanglement detection. Here we employ the continuous transverse spatial variables of photon pairs to experimentally demonstrate novel entanglement criteria based on a periodic structure of coarse-grained measurements. The periodization of the measurements allows for an efficient evaluation of entanglement using spatial masks acting as mode analyzers over the entire transverse field distribution of the photons and without the need to reconstruct the probability densities of the conjugate continuous variables. Our experimental results demonstrate the utility of the derived criteria with a success rate in entanglement detection of $\sim60\%$ relative to $7344$ studied cases.Comment: V1: revtex4, 10 pages, 4 figures + supp. material (4 pages, 1 figure) V2: Substantial revisions implemented both in theory and experimental data analysi

The transition from a coherent optical vortex to a Rankine vortex: beam contrast dependence on topological charge

Spatially coherent helically phased light beams carry orbital angular momentum (OAM) and contain phase singularities at their centre. Destructive interference at the position of the phase singularity means the intensity at this point is necessarily zero, which results in a high contrast between the centre and the surrounding annular intensity distribution. Beams of reduced spatial coherence yet still carrying OAM have previously been referred to as Rankine vortices. Such beams no longer possess zero intensity at their centre, exhibiting a contrast that decreases as their spatial coherence is reduced. In this work, we study the contrast of a vortex beam as a function of its spatial coherence and topological charge. We show that beams carrying higher values of topological charge display a radial intensity contrast that is more resilient to a reduction in spatial coherence of the source