Rotonya Carr, a physician and mother of two, was looking for some advice on how to get her children to eat a variety of healthy foods.

"My daughter is a really good eater, and my son is on the pickier side," Carr said. Her son, Tyree, is 6; daughter Avery is 2. "He'll never choose different types of vegetables, but my daughter is quite the opposite. She loves all vegetables -- we can give her anything and she'll eat it."

Why are some kids willing to try new foods and some reluctant, even when they're raised in the same environment?

"There are genetic influences, and then there are environmental influences," said Marcia Pelchat,  an associate member emerita at the Monell Chemical Senses Center who specializes in food preferences. "You can have a picky eater and an adventurous eater in the same family."

Pelchat was at the Philadelphia Science Festival last weekend, specifically at the session called "Be a Food Psychologist!" held at Greensgrow Community Kitchen in Kensington.  She was there with Megan Haupt of Hungry Education to talk about two of her favorite topics: food cravings and food neophobia, otherwise known as picky eating.

Some parents might consider the nature-nurture finding discouraging, but Pelchat sees it as good news. "If you're a parent of a picky kid, you shouldn't beat yourself up for it," she said. "There may have been nothing that you could have done." On the other hand, there are ways to try to open your kids up to new taste experiences.

Persistence in providing a variety of healthy foods and demonstrating to your children that you value food are key. In other words, don't give up. Keep serving those vegetables with dinner every night, and keep eating them yourself.

"One of the most important things, more than genetics, is what you're familiar with. People like what they know," Pelchat said.

She strongly advises against forcing children to eat, because that can backfire and make them even pickier. Instead, with younger children Pelchat takes the unfinished food and eats it herself, saying, "Good, more for me."

Parental attitude toward food makes a big difference. Like many people, Pelchat used to think cilantro tasted like soap, but after she pushed herself to keep trying it, her perception changed. "One day I said, 'You know, I really like this stuff.' But it took a couple of years." Similarly, her son started out hating cilantro but learned to like it over time.

Haupt, a food educator who partnered with Pelchat on the event, founded Hungry Education in 2015. She works with younger children on play-based learning activities that focus on food relationships rather than nutrition -- an approach she's found successful with picky preschoolers.

"We're helping them to build a food vocabulary through things like sensory exploration and exploratory and object play," Haupt said. "The role of the senses -- tactile, sight, smell, sound -- all play a huge role in picky eating."

Haupt does an exercise called "the nose knows" where she puts fragrant foods like vanilla beans, red pepper, lemon and parsley in different jars and covers them with aluminum foil so the kids can't see it. Then she asks them to describe and draw what they smell.

"We had a little girl who smelled a vanilla bean and she was like 'Ah, this smells like birthdays!'" said Haupt.

At Monell, Pelchat conducted one of the first brain-imaging studies on food cravings, and along the way became an expert on inducing cravings in people. As Pelchat chatted about her experience as a woman in science, the children donned lab coats for a kid-appropriate reenactment of one of her experiments.

"It's torture what she's doing," Jim Dugan said as he stared at three unwrapped Hershey's Kisses lined up on the table in front of him. Pelchat was instructing Dugan's daughter Naomi, 7, and a room full of children how to conduct a chocolate craving experiment with their parents as subjects.

"Mmm, this is really good," Pelchat said through a mouthful of truffle candy. "Look at the chocolate, imagine how it would feel melting on your tongue," she said to the parents. "I want all of my helpers to watch the adults and make sure that they don't eat it."

Parents recorded their initial craving level from -1 to 5 on a rating sheet with corresponding emojis. Pelchat instructed the adults to smell the chocolate, then unwrap it and place it on the table. While they waited -- and the children watched to make sure they did not sneak a bite -- both the adults and kids picked Pelchat's brain.

"How do you get rid of a craving once you have it?" one parent asked.

"Usually it's a matter of getting away from the thing you're craving. Don't stand right next to it. Do something else that you can get really absorbed in, like reading a book or taking a walk," advised Pelchat.

When asked about cravings during pregnancy, Pelchat explained that women of childbearing age are the most susceptible. "Almost 100 percent of women 18 to 35 years of age say that they have food cravings. If you look at older women or men of any age, it's only about two-thirds or half," Pelchat said. Women usually pine for sweets, while for men it's more savory items, such as pizza and burgers.

After several minutes of listening to Pelchat explain that all cravings, from food to video games to drugs, have a similar brain-activation pattern, the parents again rated how much they wanted to eat the chocolate.

Even Carr, who described herself as "not a big chocolate eater," found her craving level went up during that time. "I was surprised," she said. "If I'm really being honest, I kind of do want this chocolate."

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