Psychologists are fairly confident that a bunch of radishes and freshly baked chocolate chip cookies tell us something significant about the nature of willpower, and those conclusions can inform the popular argument that being healthy is all a matter of “personal responsibility.” Here’s the story.

Respondents to a “taste-perception study” encountered a researcher at a table of freshly cut radishes and freshly baked cookies – in the highly aromatic room where those cookies had just been baked, no less. Half of participants were told to enjoy the veggies but not the treat, while half were given the opposite instruction. Next, researchers left their subjects alone in the room. All participants continued to adhere to directions. (While its not surprising that cookie eaters left the radishes alone, not one radish eater grabbed a cookie.) Researchers returned to declare the end of the interview, then at the last second asked for one more thing: that subjects tackle an unsolvable puzzle – tracing a complex geometric shape in its entirety without lifting their pencil from the paper. Those who had been previously tasked with avoiding cookies averaged only eight minutes on this task before quitting, while cookie eaters stuck with it for an average of 18 minutes. In their analysis, the researchers concluded that “active volition is limited and that a range of seemingly different, unrelated acts share a common resource.”

Of course marketers, salespeople and retailers have known and acted on this knowledge for a long time, and many of us know we’re being prompted to buy what’s most easily within reach. It’s just we may not be similarly aware that – intentionally or not – our environments where we live, learn, work and play cueing up choices also.

We are most vulnerable to the convenient choices for food, recreation, or activity – especially after a long day we just spent focusing disciplined energy at school or work. At the end of the day, the healthy choice has to be at least as easy to choose as the unhealthy one, because willpower is exhaustible and prompted automatic responses aren’t.