Transcranial magnetic stimulation (TMS) studies showed that watching others’ movements enhances motor evoked potentials (MEPs) amplitude of the muscles involved in the observed action (motor facilitation, MF). MF has been attributed to a mirror neuron system mediated by an excitability increment of primary motor cortex. It is still unclear whether the meaning an action assumed when performed in an interpersonal exchange context could affect MF. This study aims at exploring this issue by measuring MF induced by the observation of the same action coupled with opposite reward values (gain VS loss) in an economic game. Moreover, the interaction frame was manipulated by showing the same actions within different economic games, the Dictator Game (DG) and the Theft Game (TG). Both games involved two players: a Dictator/Thief and a receiver. Experimental participants played the game always as receivers whereas the Dictator/Thief role was played by our confederates. In each game Dictator/Thief’s choices were expressed by showing a grasping action of one of two cylinders, previously associated to fair/unfair choices. In the DG the dictator decides whether to share (gain condition) or not (no-gain condition) a sum of money with the receiver, while in TGs the thief decides whether to steal (loss condition) or not to steal (no-loss condition) it from the participants. While the experimental subjects watched the videos showing these movements, a single TMS pulse was delivered to their motor hand area and a MEP was recorded from the right FDI muscle. Results show that, in the DG, MEPs were modulated by status quo modification, i.e. when the dictator decided to share her/his sum of money, when this was more salient. The same was true for the TG, where the reverse happened: MEPs amplitude was higher for trials in which the thief decided to steal the participants’ money, thus changing the status quo, in blocks when the status quo maintenance occurred more often. Data support the hypothesis that the economic meaning of the observed actions differently modulates MEPs amplitude, pointing at an influence on MF exerted by a peculiar interaction between economic outcomes and variation of the subjects’ initial status quo.

Fair Play Doesn’t Matter: MEP Modulation as a Neurophysiological Signature of Status Quo Bias in Economic Interactions

ZARRI, Luca;
2014

Abstract

Transcranial magnetic stimulation (TMS) studies showed that watching others’ movements enhances motor evoked potentials (MEPs) amplitude of the muscles involved in the observed action (motor facilitation, MF). MF has been attributed to a mirror neuron system mediated by an excitability increment of primary motor cortex. It is still unclear whether the meaning an action assumed when performed in an interpersonal exchange context could affect MF. This study aims at exploring this issue by measuring MF induced by the observation of the same action coupled with opposite reward values (gain VS loss) in an economic game. Moreover, the interaction frame was manipulated by showing the same actions within different economic games, the Dictator Game (DG) and the Theft Game (TG). Both games involved two players: a Dictator/Thief and a receiver. Experimental participants played the game always as receivers whereas the Dictator/Thief role was played by our confederates. In each game Dictator/Thief’s choices were expressed by showing a grasping action of one of two cylinders, previously associated to fair/unfair choices. In the DG the dictator decides whether to share (gain condition) or not (no-gain condition) a sum of money with the receiver, while in TGs the thief decides whether to steal (loss condition) or not to steal (no-loss condition) it from the participants. While the experimental subjects watched the videos showing these movements, a single TMS pulse was delivered to their motor hand area and a MEP was recorded from the right FDI muscle. Results show that, in the DG, MEPs were modulated by status quo modification, i.e. when the dictator decided to share her/his sum of money, when this was more salient. The same was true for the TG, where the reverse happened: MEPs amplitude was higher for trials in which the thief decided to steal the participants’ money, thus changing the status quo, in blocks when the status quo maintenance occurred more often. Data support the hypothesis that the economic meaning of the observed actions differently modulates MEPs amplitude, pointing at an influence on MF exerted by a peculiar interaction between economic outcomes and variation of the subjects’ initial status quo.
TMS; MEP; Motor Facilitation; Economic Games; Neuroeconomics; Status Quo Bias
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11562/745962
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