. 2011 Dec 23;8(2):216–223. doi: 10.1093/scan/nsr088

Table 1.

The four decision situations and their underlying payoff-structures (A1/B1 A2/B2) including percentages of subjects choosing A1/B1 in each situation

Decision situation	Payoff structure	Percentage of subjects choosing A1/B1 (mean ± SD)
Pure self-interest (PSI)	A1>A2, B1 = B2	98.64 (±2.49)
Pure self-interest (PSI)	e.g. 10/20 5/20	98.64 (±2.49)
Noncostly donation (NCD)	B1>B2, A1 = A2	97.9 (±3.22)
Noncostly donation (NCD)	e.g. 5/40 5/10	97.9 (±3.22)
Efficiency (E)	A1>A2, B1>B2	99.48 (±0.93)
Efficiency (E)	e.g. 20/40 10/20	99.48 (±0.93)
Costly donation (CD)	A1<A2, B1>B2	17.49 (±25.17)
Costly donation (CD)	e.g. 5/80 20/40	17.49 (±25.17)

Notes: A: subject's payoff, B: charity's payoff, A1/B1: first alternative, A2/B2: second alternative. Note that the trials are randomly drawn from all possible combinations of decision situations. This results in a randomization of the order of payoff alternatives (see Methodological Details in Supplementary Data).