Shoppers who bring reusable tote bags to the store are more likely to buy organic foods, according to a new study out of Duke University and Harvard Business School.

But here’s the better part: while those shoppers are filling their bags with organic food, they were also 7.3 percent more likely to buy, well, a little treat. The study looked at shoppers in one California supermarket between 2005 and 2007, and found that their purchases of so-called indulgent items went up when they brought their own bags.

The conclusion from the study? That bringing your own bag makes you feel a little smug. A little like you earned it. The researchers described it as being “licensed” to buy treats.

One important exception: parents with reusable totes actually bought fewer indulgent items.

Good job, moms and dads.