There’s an old-timey comfort to heading out to a family farm stand and who doesn’t have fond memories of a family picnic at a pick-your-own fruit farm operation? Psychologists say that the warm, bubbly feeling you get during a farm outing may have something to do with an interesting part of the tradition: the honor payment system.

NPR’s Deborah Franklin says that customers love Swanton Berry Farm in Santa Cruz, Calif., and not just because of the sumptuous, certified organic, pick-your-own berries. In fact, “Swanton founder Jim Cochran says his stand has thrived for years on the honor payment system,” according to Franklin.

That doesn't surprise social psychologist Michael Cunningham of the University of Louisville who has used "trust games" to investigate what spurs good and bad behavior for the last 25 years. For many people, Cunningham says, trust seems to be at least as strong a motivator as guilt. He thinks he knows why.

"When you sell me something I want and trust me to pay you even when you're not looking, you've made my life good in two ways," Cunningham tells (NPR’s Salt blog.) "I get something delicious, and I also get a good feeling about myself. Both of those things make me feel good about the world— that I'm in a good place. And I also see you as a contributor to that good — as somebody I want to reward. It's a win win."

Sure, some patrons will abuse the honor system privilege. And it’s no way for a conventional farm to operate. Can you imagine allowing a multinational chicken corporation to pay whatever they feel like for your birds?

Essentially, though, psychologists say that the warm, fuzzy feeling  you get from using the honor payment system at your local family farm adds to your happiness – just like the cider donut you paid for (at a fair price.)