YOKOTA Kunihiro    Department   Hiroshima shudo University  The Faculty of Health Sciences    Position   Professor
Date	2023/04/19
Presentation Theme	Can the behavioural equilibrium follow the 80/20 rule in human beings?
Conference	Anual conference for the European Human Behavior and Evilution Association 2023
Promoters	The European Human Behavior and Evilution Association
Conference Type	International
Presentation Type	Poster
Contribution Type	Collaborative
Venue	University of London, UK
Publisher and common publisher	Minami Natsumeda,, Daisuke Nakanishi.
Details	Objective(s): The 80/20 principle is an empirical rule whereby a group or an organization are composed of both, workers and non-workers. Equilibrium based on the 80/20 rule has been observed in ant colonies, which can be explained by the kin selection theory. However, humans cooperate with non-kin, even with strangers. The question is whether the 80/20 rule can be observed among human beings. Previous research argued, theoretically, that stable behavioural equilibrium following the 80/20 rule, occurred in a situation with the payoff structure of diminishing returns (e.g., Producer-Scrounger equilibrium). As there is little empirical evidence of the 80/20 rule phenomenon among humans, we conducted an experiment using two types of group tasks (disjunctive/additive). We hypothesized that equilibrium as per the 80/20 rule, should be observed in the disjunctive task because it theoretically included the payoff structure of diminishing returns. Methods: Seventy-five undergraduates participated in the experiment and performed five trials of a calculation task in groups of four or five. Experimental rewards were determined either by the outcome of one group member who solved the most answers (disjunctive task condition) or by the average of all members’ outcomes (additive task condition). Results: In disjunctive tasks, there was a stable difference between the performance of the higher and lower rank members across all trials. In contrast, in additive tasks, the behavioural variance within a group converged over trials. Conclusion(s): Equilibrium based on the 80/20 rule was observed in disjunctive, but not in, additive tasks.