Table 1.

Distribution of answers on whether participants’ decisions depended on others’ contribution

	Treatment
	Human		Computer
Type	Yes*	No	Yes	No
Free rider	5	48	13	67
Conditional cooperator	47	2	27	0
Humped cooperator	12	1	10	0
Other	2	0	0	0

^*Response to the question of whether participants’ contributions depended on others’ contributions. Question asked: “In the decision you just made, did your contribution depend on the contributions of other members of your group?” The six confused participants were not included in the analysis of motives. N = 117 for each treatment.