RESUMEN
Objective:To investigate the effect of a single-trial transcranial direct current stimulation(tDCS) of the dorsolateral prefrontal cortex (DLPFC) on fairness-related decision-making behavior.Methods:From September 2018 to February 2019, a total of 60 healthy participants between the ages of 18 and 45 were enrolled.Then, the participants were randomly divided into 3 groups with 20 in each group to receive left anode stimulation/right cathode stimulation (left anode /right cathode group), left cathode/right anode stimulation (left cathode /right anode group) or bilateral control electrodes (sham stimulation group) on the bilateral dorsolateral prefrontal cortices (DLPFC), respectively.After tDCS, the participants immediately completed the ultimatum game (UG) task as responders and a fairness questionnaire in turn.SPSS 22.0 statistical software was used to analyze the data with repeated measurement ANOVA and nonparametric test.Results:In the UG task, there was no significant difference in the acceptance rate among the three groups of participants as responders (all P>0.05). When analyzing the acceptance rate facing different proposers (" computer" and " human" ) under different fairness levels in the three stimulus types through the paired samples Wilcoxon test, it was found that the acceptance rate of the sham stimulation group to the extremely unfair proposals proposed by the human opponent was lower than that proposed by the computer(0.28 (0, 0.67), 0.44 (0.33, 0.89), Z=-2.14, P=0.032), while there was no difference in acceptance rates (both P>0.05) in the face of fair or unfair proposals proposed by computer and human opponents.The acceptance rate of the left cathode /right anode group to the unfair(0.90 (0.50, 1.00), 1.00 (0.70, 1.00), Z=-1.90, P=0.046)or extremely unfair(0.44 (0, 1.00), 0.89 (0.50, 1.00), Z=-2.73, P=0.006) proposals proposed by human opponents was significantly lower than the proposals proposed by computer opponent, and there was no differences in acceptance rate when facing fair proposals proposed by computer and human opponents ( P> 0.05). There were no significant differences in acceptance rates in the left anode /right cathode group when faced with fair, unfair, and extremely unfair schemes proposed by computer and human opponents (all P>0.05). For fairness questionnaire scores, a repeated measurements ANOVA showed that the interaction effect between group and proposer types was not significant ( F(2, 54)=2.037, P=0.140), and the group main effect was not significant ( F(1, 54)=0.165, P=0.848), but the proposer type main effect was significant ( F(1, 54)=6.363, P=0.015), indicating that the fairness questionnaire score in the face of the human opponents was lower than when facing the computer opponents( P<0.05). Conclusion:Although a single-trial tDCS on bilateral DLPFC has no significant effect on the overall acceptance rate of fairness-related decision-making, it affects the decision-making of unfair distribution scheme proposed by human or computer.
RESUMEN
Este trabajo se propone examinar la influencia de las envidias benigna y maligna en las ofertas del proponente en condición de envidiado y envidioso en el Juego del Ultimátum en 172 estudiantes universitarios de Córdoba, Argentina. Se empleó un diseño factorial interindividual 2 (tipo de envidia: maligna y benigna) X 2 (condición del participante: envidiado y envidioso) con un grupo adicional de control absoluto. Se compararon las ofertas en el Juego del Ultimátum según la condición experimental. No se observaron diferencias estadísticamente significativas entre las distintas condiciones. Sin embargo, se observó que la preocupación por ser envidiado se relacionó positivamente con las ofertas en el juego.
This study aimed to examine the influence of benign and malicious envy upon offers from proponents with envious and envied status in the Ultimatum Game. Participants were 172 university students from Cordoba (Argentina). A factorial inter-subject 2 (type envy: benign and malicious) 3 2 (condition of the participant: envied and envious) design was used, with an additional absolute control group. Offers in the Ultimatum Game were compared according to experimental condition. No statistically significant differences were observed between the different conditions. Nevertheless, the fear of being envied was positively associated with offers in the Ultimatum Game.