Just when you thought it was safe to go back in the supermarket – nibbling free samples like no one is watching – the Cornell Food and Brand Lab has your number: 28.

Shoppers who first received a sample apple slice purchased 28 percent more fruits and vegetables. And those suggestible souls who took a cookie sample instead? Their fate is reported by the lab’s Aner Tal and Brian Wansink, in a special issue of the journal, Psychology & Marketing, in an article subtitled “Healthy Samples Prime Healthier Choices.”

“What this teaches us,” Tal explains, “is that having a small healthy snack before shopping can put us in a healthier mindset and steer us toward making better food choices.”

The same journal has a second article by Wansink, the John Dyson Professor of Consumer Behavior in the College of Agriculture and Life Sciences, director of the Cornell Food and Brand Lab subtitled “Changing Behavior Using the CAN Approach and Activism Research.”

With the “CAN approach,” Wansink explains in a meta-analysis of 112 previous studies, “A healthy diet can be as easy as making the healthiest choice the most convenient, attractive and normal.”

Wansink’s book, “Slim by Design,” recounts scientific research studies that informed recommendations like the CAN approach, along with anecdotes about experiments in food-consumer behavior, misbehavior and consumption.

In fact, priming people with apple slices before they shop demonstrates a CAN approach principle. By offering apple slices, the store is making it seem normal to select healthy items such as apples, and nudges shoppers to select similarly, healthy items to purchase. For instance, those cookie-sampling shoppers actually didn’t buy much more junk food, compared to “control” shoppers who received no samples at all.

The significant behavior change was the increase in healthful shopping by apple-primed people. As the first article explains, “Priming is known to have a broad variety of effects on judgment and behavior. The activation of concepts through priming can influence what a person sees, how they think and how they act. Priming both influences information processing and triggers behavior.”

Two other, laboratory-based experiments – with free-sample priming, “control” shoppers who got nothing and virtual shopping on computers by all participants – were included with the supermarket study.

In one experiment, to show the power of product branding, priming samples were otherwise identical bottles of chocolate milk, alternately labeled HEALTHY WHOLESOME CHOCOLATE MILK or RICH INDULGENT CHOCOLATE MILK. It was the exact same chocolate milk. Same lingering chocolatey taste as shoppers pushed virtual carts through the virtual grocery store – brimming with a variety of healthy (low-calorie) and unhealthy (high-calorie) options. Yet, experimental subjects – who were primed with RICH INDULGENT – shopped as if they were, both rich and indulgent.

Then there’s self-priming, according to Tal, a postdoctoral research associate in the Dyson School: “You probably can’t count on a freshly sliced apple samples everyday at your grocery store. Bring your own apple.”

The shopping study was funded by Cornell University.