چکیده (انگلیسی):

Objective: This study tests the hypothesis that the decision-making process in humans is often based on the fairness rather than the monetary gain/loss, when they are confronted with a choice between fairness and monetary gain/loss. Methods: The classical Ultimatum Game (UG) is used as the experimental paradigm to quantify the threshold crossover-point to switch the decision from rejection to acceptance. The fairness stimulus-response function is used for quantifying the decision threshold and the co-variation relationship between fairness and monetary gain/loss. Results: The results show that the level of fairness perception is always 27.5% lower for the rejection decision than the acceptance decision, irrespective of the offer-ratio (i.e., monetary gain/loss) or the baseline level of fairness for that decision. The data also show a co-variation relationship between fairness and offer-ratio (monetary gain/loss), but such proportionality relationship is decoupled at the even-split singularity point. The analysis shows that the decision crossover threshold is located at a slightly unfair perception, indicating tolerance to some unfairness in the decision. This suggests that a rejection decision is made when the unfairness perception threshold is reached. Conclusion: These analyses validated the hypothesis that the decision to accept/reject the monetary offer is logically consistent using the fairness criterion as the threshold for decision along the fairness-axis — even for accepting inequitable offers or rejecting hyper-equitable offers, irrespective of the amount of monetary gain/loss. The apparent decision based on the monetary gain/loss criterion is only a side effect of the co-variation between fairness and monetary gain.