People who grocery shop with their own reusable bags are doing the environment a solid, but, oddly, maybe not their waistlines. Researchers at Duke and Harvard business schools studied 2 million trips to a California supermarket to see if carrying bags from home had any effects on what people bought, and they found it did: A person with her or his own tote is 13 percent more likely to buy organic products — and 7 percent more likely to load the bag up with junk food.
Why? They’re basically treating themselves for saving the Earth; the authors say it’s called the “licensing effect,” this idea that being awesome in one area permits you to slack off in another because they sort of cancel each other out, like permitting yourself to order cheese fries because you went to the gym. At any rate, plastic bags are out of fashion almost everywhere now, so there could be a weird side effect to all this ecoconsciousness.