Dynamic remodeling of in-group bias during the 2008 presidential election

Abstract

People often favor members of their own group, while discriminating against members of other groups. Such in-group favoritism has been shown to play an important role in human cooperation. However, in the face of changing conflicts and shifting alliances, it is essential for group identities to be flexible. Using the dictator game from behavioral economics, we demonstrate the remodeling of group identities among supporters of Democratic presidential candidates Barack Obama and Hillary Clinton. After Clinton's concession in June 2008, Democrats were more generous toward supporters of their own preferred candidate than to supporters of the other Democratic candidate. The bias observed in June persisted into August, and disappeared only in early September after the Democratic National Convention. We also observe a strong gender effect, with bias both appearing and subsiding among men only. This experimental study illustrates a dynamic change in bias, tracking the realignment of real world conflict lines and public efforts to reconstitute group identity. The change in salient group identity we describe here likely contributed to the victory of Barack Obama in the 2008 presidential election.

Fig. 1.

Significant in-group favoritism exists among men in June (A) and August (B), but not September (C). Average transfer to supporters of the same candidate (In-group transfers, blue) and supporters of the other candidate (out-group transfers, red) are shown. Male Democrats transferred significantly more to in-group members before the DNC compared with after the DNC (2-tailed Wilcoxon rank-sum, P = 0.013). There was no significant pre-DNC vs. post-DNC difference, however, in the amount transferred by male Democrats to out-group members (2-tailed Wilcoxon rank-sum, P = 0.78). P values displayed in the figure were determined by 1-tailed Wilcoxon rank-sum tests. Error bars indicate standard error of the mean.

Fig. 2.

The same pattern of changing in-group favoritism exists among supporters of Barak Obama and Hillary Clinton. Significant in-group bias exists before the Democratic National Convention (June and August data aggregated) among male Obama supporters (A) and male Clinton supporters (C). There is no significant in-group bias after the DNC among either Obama supporters (B) or Clinton supporters (D). Comparing the level of pre-DNC bias, there is some indication that Clinton supporters discriminated more than Obama supporters. There is no significant difference in transfers to in-group members among men before the DNC (Obama to Obama: $3.18, Clinton to Clinton: $2.92; 2-tailed Wilcoxon rank-sum, P = 0.72). However, there is a significant difference in male pre-DNC transfers to out-group members (Obama to Clinton: $1.88, Clinton to Obama: $0.77, 2-tailed Wilcoxon rank-sum, P = 0.027). P values displayed in the figure are determined by 1-tailed Wilcoxon rank-sum tests. Error bars indicate standard error of the mean.