CHIMPANZEES ARE VENGEFUL BUT NOT

SPITEFUL

Jensen, Call, Tomasello

Becca Taylor

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?

STUDY 1: FRUSTRATION VS. SPITE

Condition Tray Location

Tray Content

s

Partner

Present?

Self-Feeding Actor Food Yes

Partner Feeding Partner Food Yes

Nobody Feeding Partner Food No

Baseline Both Inedibles No

PA

STUDY 1: FRUSTRATION VS. SPITE

Condition Tray Location

Tray Content

s

Partner

Present?

Self-Feeding Actor Food Yes

Partner Feeding Partner Food Yes

Nobody Feeding Partner Food No

Baseline Both Inedibles NoSuggesting chimps were motivated by Frustration at out of reach food rather than by the personally disadvantageous situation – this is not spiteful behavior.

STUDY 2: LOSS VS. THEFT

Condition

Tray Location

Tray Content

s

Partner

Present?

Baseline Partner Inedibles No

Loss Actor Partner Food No

Outcome Disparity

Actor Partner Food Yes

Theft Actor Partner Food Yes

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.

STUDY 2: LOSS VS. THEFT

Condition

Tray Location

Tray Content

s

Partner

Present?

Baseline Partner Inedibles No

Loss Actor Partner Food No

Outcome Disparity

Actor Partner Food Yes

TheftActor Partner Food YesChimps reacted vengefully against

an individual who stole from them, but not spitefully to personally disadvantageous outcomes

STUDY 2: LOSS VS. THEFT – EXPLAINING RESULTS Identified Five Variables that might have affected the results:

Kinship, Dominance, Reciprocity, Time and Arousal

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.

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.

ANY QUESTIONS?