Does "return their money" mean "pay back their/the participants' money"?

Context:

A growing body of work has established that in laboratory studies, subjects who are less trusting of their peers make less money in investment and economic scenarios. For instance, participants in one 2009 study underestimated how many partners would return their money in an economics game, so they underinvested and wound up with lower earnings than they could have. A paper, published online in May in the Journal of Personality and Social Psychology, now finds some real-world evidence of the financial harm of cynicism.

More:

http://www.scientificamerican.com/article/cynicism-may-cost-you/