FIGURE 2. The punishment threat for the lowest transfer level as perceived by the dictators.
From the following article:
Helen Bernhard, Urs Fischbacher and Ernst Fehr
Nature 442, 912-915(24 August 2006)
doi:10.1038/nature04981
The punishment threat subjectively perceived is important, because higher expectations about punishment induce more compliance with the sharing norm. In those conditions where the recipient (B) and the third party (C) belong to the same group (that is, in conditions ABC and BC), dictators perceive a higher punishment threat than in conditions where B and C belong to different groups (that is, in conditions AB and AC).