Setup of the chimpanzee study.

<p>Illustration of the experimental setup for chimpanzees, viewed from the experimenter's point of view. The observed condition (pictured here) consisted of three different roles, subject (left), observer (middle) and receiver (right). In the stealing task (left), subjects could steal food from the receiver by collapsing the food platform. In the helping task (left), subjects could give food to the recipient, which they couldn't obtain otherwise.</p

Setup of the child study.

<p>Illustration of the experimental setup for children, viewed from the subject's perspective. In the stealing task (left) subjects could only finish their sticker sheet if they took a star-shaped sticker from sticker sheet 2, destined for an anonymous next participant. In the helping task (right) subjects received one additional sticker. They had the option of either leaving the sticker for the next participant or taking it home.</p

Results_Trust

Results_Trus

Results of the child study.

<p>Mean percentage of responses as a function of task and condition in Experiment 1.</p

Results of the chimpanzee study.

<p>Mean percentage of responses as a function of task and condition in Experiment 2.</p

Summer Student Report

This document contains my summer student report for every application I've developed or upgraded in the period of 3 months (13/06- 12/09

Methods and Statistics from Social disappointment explains chimpanzees' behaviour in the inequity aversion task

Chimpanzees’ refusal of less-preferred food when an experimenter has previously provided preferred food to a conspecific has been taken as evidence for a sense of fairness. Here, we present a novel hypothesis—the social disappointment hypothesis—according to which food refusals express chimpanzees' disappointment in the human experimenter for not rewarding them as well as they could have. We tested this hypothesis using a two-by-two design in which food was either distributed by an experimenter or a machine and with a partner present or absent. We found that chimpanzees were more likely to reject food when it was distributed by an experimenter rather than by a machine and that they were not more likely to do so when a partner was present. These results suggest that chimpanzees’ refusal of less-preferred food stems from social disappointment in the experimenter and not from a sense of fairness

Video S3 Machine Partner Condition from Social disappointment explains chimpanzees' behaviour in the inequity aversion task

Chimpanzees’ refusal of less-preferred food when an experimenter has previously provided preferred food to a conspecific has been taken as evidence for a sense of fairness. Here, we present a novel hypothesis—the social disappointment hypothesis—according to which food refusals express chimpanzees' disappointment in the human experimenter for not rewarding them as well as they could have. We tested this hypothesis using a two-by-two design in which food was either distributed by an experimenter or a machine and with a partner present or absent. We found that chimpanzees were more likely to reject food when it was distributed by an experimenter rather than by a machine and that they were not more likely to do so when a partner was present. These results suggest that chimpanzees’ refusal of less-preferred food stems from social disappointment in the experimenter and not from a sense of fairness

Video S4 Machine No Partner Condition from Social disappointment explains chimpanzees' behaviour in the inequity aversion task

Chimpanzees’ refusal of less-preferred food when an experimenter has previously provided preferred food to a conspecific has been taken as evidence for a sense of fairness. Here, we present a novel hypothesis—the social disappointment hypothesis—according to which food refusals express chimpanzees' disappointment in the human experimenter for not rewarding them as well as they could have. We tested this hypothesis using a two-by-two design in which food was either distributed by an experimenter or a machine and with a partner present or absent. We found that chimpanzees were more likely to reject food when it was distributed by an experimenter rather than by a machine and that they were not more likely to do so when a partner was present. These results suggest that chimpanzees’ refusal of less-preferred food stems from social disappointment in the experimenter and not from a sense of fairness