Tilburg University

About: Tilburg University is a education organization based out in Tilburg, Noord-Brabant, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 5550 authors who have published 22330 publications receiving 791335 citations.

Supply and demand determine the market value of food providers in wild vervet monkeys

Abstract: Animals neither negotiate verbally nor conclude binding contracts, but nevertheless regularly exchange goods and services without overt coercion and manage to arrive at agreements over exchange rates. Biological market theory predicts that such exchange rates fluctuate according to the law of supply and demand. Previous studies showed that primates pay more when commodities become scarcer: subordinates groomed dominants longer before being tolerated at food sites in periods of shortage; females groomed mothers longer before obtaining permission to handle their infants when there were fewer newborns and males groomed fertile females longer before obtaining their compliance when fewer such females were present. We further substantiated these results by conducting a 2-step experiment in 2 groups of free-ranging vervet monkeys in the Loskop Dam Nature Reserve, South Africa. We first allowed a single low-ranking female to repeatedly provide food to her entire group by triggering the opening of a container and measured grooming bouts involving this female in the hour after she made the reward available. We then measured the shifts in grooming patterns after we added a second food container that could be opened by another low-ranking female, the second provider. All 4 providers received more grooming, relative to the amount of grooming they provided themselves. As biological market theory predicts, the initial gain of first providers was partially lost again after the introduction of a second provider in both groups. We conclude that grooming was fine-tuned to changes in the value of these females as social partners.

Appraisal patterns of envy and related emotions

Abstract: Envy is a frustrating emotion that arises from upward social comparison. Two studies investigated the appraisals that distinguish benign envy (aimed at improving one’s own situation) from malicious envy (aimed at pulling down the superior other). Study 1 found that appraisals of deservingness and control potential differentiated both types of envy. We manipulated these appraisals in Study 2 and found that while both did not influence the intensity of envy, they did determine the type of envy that resulted. The more a situation was appraised as undeserved, the more participants experienced malicious envy. Benign envy was experienced more when the situation was not undeserved, and the most when the situation was appraised as both deserved and controllable. The current research also clarifies how the types of envy differ from the related emotions admiration and resentment.