Any regular eater could gag thinking about somebody eating something disgusting, says Pelchat. For picky eaters, there are simply many more yucky foods. Some may have been affected by a lack of variety when they were young. Children who aren’t introduced to solid foods and certain textures such as steak early enough may never feel comfortable manipulating it in their mouth. “They may, in fact, be more likely to gag on it,” Pelchat says.

Parental and cultural expectations also can influence a person’s openness to new foods, says Karen Le Billon, author of the book French Kids Eat Everything, which chronicles how her young daughters, who were 5 and 2 at the time, went from being picky eaters to happy omnivores during a year the family spent in France. Le Billon’s daughters eat everything now, from sushi to seaweed and from beets to bulgur — even something as exotic as Roquefort cheese.

The French believe children can enjoy eating well, she says. They just need to be shown the way. “Feeding kids doesn’t have to be a hassle,” says Le Billon, whose next book, Getting to Yum: 7 Secrets for Raising Eager Eaters, is due out next April.

Le Billon says that French parents tell children, “Taste this; you’ll like it,” which works better than the North American approach — “Eat this; it’s good for you” — that pushes nutrition. Plus, the French know it may take multiple taste tests before a child will accept a new food.

School lunches in France reinforce the idea that food is an adventure in the development of taste, Le Billon says. Preschoolers in the town of Versailles have been known to dive into an aristocratic-sounding four-course meal that includes grapefruit-and-lettuce salad with basil vinaigrette dressing and sautéed pork with curry-coconut sauce and white navy beans. “I do think they have food education figured out,” Le Billon says.

Even before their first birthdays, French infants are introduced to leeks, asparagus and eggplant, according to Le Billon. Toddlers move fairly quickly through the picky-eating stage that hits around ages 2 or 3. You wouldn’t expect your child to linger in the tantrum or “no” phases for life, says Le Billon. “Neither would you expect a child to be picky for life.”

Still, Zucker, who has co-authored the first major study on picky eating among adults, is not convinced that adult picky eaters could have changed their ways in a different environment. According to her analysis of survey data, the parents of picky eaters may be role models of eating diversity yet some of their children may still turn out to be picky eaters.

The families Zucker works with have tried everything, she says. It may just be too hard for parents of the really picky eaters to change their child’s eating habits. “They would have to be food therapists,” she says. “It’s just hard.”

Sandra Yin wrote about plastic wrap, Dr. Brown’s soda and military slang for The Oxford Encyclopedia of Food and Drink in America. She wrote about the help available to navigate the complicated health-care system in American Way’s May 1, 2013, issue.