Chimpanzees are vengeful but not spiteful

1. Chimpanzees are vengeful but not spiteful Jensen, Call, Tomasello Becca Taylor

2. Fairness and Punishment • The goal of this study was to gauge chimpanzees’ sense of fairness: • Will they react to personally harmful actions by retaliation against the perpetrator? • Will they react negatively towards personally disadvantageous outcomes by behaving spitefully towards conspecifics’ fortunes?

3. Study 1: Frustration Vs. Spite P A

4. Study 1: Frustration Vs. Spite Suggesting chimps were motivated by Frustration at out of reach food rather than by the personally disadvantageous situation – this is not spiteful behavior.

5. Study 2: Loss Vs. Theft • In the Loss and Outcome Disparity conditions the experimenter moves the food away from the Actor while the actor is eating; • In the Theft condition the Partner has access to a rope to pull the tray away from the Actor.

6. Study 2: Loss Vs. Theft Chimps reacted vengefully against an individual who stole from them, but not spitefully to personally disadvantageous outcomes

7. Study 2: Loss Vs. Theft – explaining Results • Identified Five Variables that might have affected the results: • Kinship, Dominance, Reciprocity, Time and Arousal

8. Study 2: Loss Vs. Theft – explaining Results: Arousal • Arousal was measured in times displays and tantrums were exhibited by actors over the various conditions. • Chimps were more aroused by theft than loss, but not significantly more by theft than O.D. or by O.D. than by loss. • Chimps were more likely to collapse the table when aroused.

9. Conclusions: Vengeful, Not Spiteful • At least on a short time scale chimps are retaliatory – Retribution would be beneficial as a punishment naturally, • But here, we don’t see that, perhaps because benefits outweighed the costs of stealing. • Not spiteful: the goal of chimps’ actions were not to decrease conspecifics’ welfare. Spitefulness may be a uniquely human phenomenon.

10. Any Questions?