Beauty matters: social preferences in a three-person ultimatum game

Abstract

Preference for beauty is human nature, as previous behavior studies have supported the notion of "beauty premium" in which attractive people were more easily to get promoted and receive higher salaries. In the present study, 29 males were recruited to participate in a three-person ultimatum game (UG) including a proposer, a responder and a powerless third player. Each subject, playing as the responder, had to decide whether to accept an offer from the allocator both for himself and a female third person. We aimed to elucidate how the facial attractiveness of the female subject affected the male subjects' fairness and decision-making in social exchanges. Frontal feedback-related negativity (FRN) in response to four offers in an attractive-face condition revealed no significant differences between offers; however, when the companion was an unattractive female, an "unfair/fair" offer, which assigned a lower share to the responder and a fair share to the third player, elicited the largest FRN. Furthermore, when the third player was offered the smallest amount ("fair/unfair" offer), a larger FRN was generated in an attractive-face condition than unattractive-face condition. In the "unfair/fair" offer condition in which subjects received a smaller allocation than the third person, the beauty of their female counterparts attenuated subjects' aversion to inequality, resulting in a less negative FRN in the frontal region and an increased acceptance ratio. However, the influence of the third player's facial attractiveness only affected the early evaluation stage: late P300 was found to be immune to the "beauty premium". Under the two face conditions, P300 was smallest following an "unfair/fair" offer, whereas the amplitudes in the other three offer conditions exhibited no significant differences. In addition, the differentiated neural features of processing facial attractiveness were also determined and indexed by four event-related potentials (ERP) components: N170, frontal N1, N2 and late positive potentials (LPPs).

Fig 1. A single trial of the experimental procedure.

Participants first saw either an attractive face or an unattractive face before the presentation of the offers. They made their choice by pressing the keypad and had unlimited time to make a decision. Screen then showed the final payoffs.

Fig 2. The reaction time and acceptance ratio of four offers in two face conditions.

(*p<0.05; **p<0.01).

Fig 3. The ERP grand-average waveforms of FRN at Fz in two face conditions.

The time window for FRN was 290-370ms.

Fig 4. The comparison of the grand-average waveforms of FRN for the “unfair/fair” and “fair/unfair” offers at Fz and topographical maps.

The time window for FRN was 290-370ms. The four maps on the right illustrate the topographical distribution of FRN with the time window “290-370ms” in the corresponding face condition. The bar chart depicts the comparison between the mean amplitude of the FRN for the “fair/unfair” and “unfair/fair” offers in two face conditions. The bar for the topographical map ranges from +3μv to -3μv. (*p<0.05; **p<0.01).

Fig 5. The ERP grand-average waveforms of P300 for four offers in the two face conditions at Pz and topographical maps for the four offer conditions.

The time window for P300 was 400-600ms and the bar for the topographical map ranges from +6μv to -6μv.

Fig 6. The ERP grand-average waveforms of N1, N2 and LPP at the midline Fz, FCz, Cz, and Pz, and N170 at P7, P8, PO7 and PO8 for attractive face and unattractive face conditions.

The time window was 150-180ms for N170, 110-130ms for N1, 280-260ms for N2, and 450-650ms for LPP.