We study the mutual influence of authority and persuasion in the flow of opinion. Many social organizations are characterized by a hierarchical structure where the propagation of opinion is asymmetric. In the normal flow of opinion formation a high-rank agent uses its authority (or its persuasion when necessary) to impose its opinion on others. However, agents with no authority may only use the force of its persuasion to propagate their opinions. In this contribution we describe a simple model with no social mobility, where each agent belongs to a class in the hierarchy and has also a persuasion capability. The model is studied numerically for a three levels case, and analytically within a mean field approximation, with a very good agreement between the two approaches. The stratum where the dominant opinion arises from is strongly dependent on the percentage of agents in each hierarchy level, and we obtain a phase diagram identifying the relative frequency of prevailing opinions. We also find that the time evolution of the conflicting opinions polarizes after a short transient.

We study the effect of the social stratification on the wealth distribution on a system of interacting economic agents that are constrained to interact only within their own economic class. The economical mobility of the agents is related to its success in exchange transactions. Different wealth distributions are obtained as a function of the width of the economic class. We find a range of widths in which the society is divided in two classes separated by a deep gap that prevents further exchange between poor and rich agents. As a consequence, the middle wealth class is eliminated. The high values of the Gini indices obtained in these cases indicate a highly unequal society. On the other hand, lower and higher widths induce lower Gini indices and a fairer wealth distribution.

No abstract

After mating, the physiology of Drosophila females undergoes several important changes, some of which are reflected in their rest-activity cycles. To explore the hypothesis that mating modifies the temporal organization of locomotor activity patterns, we recorded the fly activity by a video tracking method. Monitoring rest-activity patterns under light/dark (LD) cycles indicated that mated females lose their ability to anticipate the night-day transition, in stark contrast to males and virgins; this postmating response is mediated by the sex peptide (SP) acting mainly on pickpocket (ppk) expressing neurons, since reducing expression of the SP receptor (SPR) in these neurons restores the ability to anticipate the LD transition in mated females. We further provide evidence of connectivity between PPK+ neurons and the pigment-dispersing factor (PDF)-positive ventral lateral neurons (sLNv), which play a central role in the temporal organization of daily activity. Since PDF has been associated to the generation of the morning activity peak, we hypothesized that the mating signal could modulate PDF levels. Indeed, mated females have reduced PDF levels at the dorsal protocerebrum; moreover, SPR downregulation in PPK+ neurons mimics PDF levels observed in males. In sum, our results are consistent with a model whereby mating-triggered signals reaches clock neurons in the fly central nervous system to modulate the temporal organization of circadian behavior according to the needs of the new status.Author SummaryAfter mating, Drosophila females undergoes striking behavioral changes, specially in their activity patterns. Despite some of the circuits that deliver mating signals to the female brain are known the connection with the circadian network has not been explored in detail. Here, we show that mating changes the onset of daily activity, masking a central function of the clock. This modulation is mediated by the sex peptide (transferred during courtship) acting on PPK+ neurons, which, in turn, directly contact PDF+ neurons, responsible for the increase of the activity that precedes dawn. Thus, our work identifies a postmating response directly related to the circadian clock, and begins to unravel the underlying neuronal circuit.