| 研究実績の概要 |
The objectives of the project were attained or are will be attained with results published in academic journals and presented at conferences (Japan, France, Scotland, USA). (1) Dogs that see somebody refuse to help their owner solve a task (getting a toy out of a small container) avoid taking food from the non-helper in the presence of a neutral person who did not interact with the owner. (2) Dogs are also studied for social evaluation with a third-party exchange of objects. The exchange is reciprocal (the two actors exchange items with each other) or non-reciprocal (one actor receives items from the other, but then refuses to reciprocate). (3) Do squirrel monkeys also show a bias against third parties who fail to reciprocate? We observed a similar avoidance of non-reciprocators as in capuchin monkeys. Unlike capuchins, however, the squirrel monkeys also showed a positive preference for reciprocating third-party exchangers. (4) Combining third-party-based evaluation with a delay of gratification procedure, we found that after witnessing an unfair exchange, capuchins were less likely to wait for pieces of food to accumulate within reach (delay of gratification) when the food was transferred by the non-reciprocator but only when the total amount of food available was unknown to the monkey, i.e., there was a situation of uncertainty.
We have also obtained positive data on in-group (intra-species) preferences in capuchins, but not squirrel monkeys, in a third-party situation in which one human actor gives food to a conspecific and another gives food to an allo-specific.
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