Food, Belief and the Rules Children Build to Understand the World

Long before children can explain their reasoning, they’re already building theories about how people think and behave. They are learning what counts as a rule, how much these rules can be bent and when people are more likely to bend their beliefs. 

Two recently published papers by Tamar Kushnir, professor of Psychology & Neuroscience, look at these processes in two very different settings.  

"The Cognitive Foundations of Food Moralization," published in Appetite, looks at how children begin to connect healthy eating with what is “okay” or “not okay.” "Children Expect Prior Belief Strength to Constrain Belief Revision," published in Cognition, explores what children understand about changing one’s mind. 

When healthy eating becomes a matter of morality 

Food is never just about nutrition: It’s tied to family routines, culture, memory and pleasure.  

“Food is a social act,” Kushnir says. “Families eat together, and it’s a very meaningful way of learning about your culture. We access the memories of our lives through the smell and taste of things, not just through visual and auditory information.”  

It’s also an area where children encounter rules early on. Adults tell them to eat their vegetables, stop eating so much candy or clean their plate. 

Over time, children may begin to understand food choices not only in terms of taste or health, but also in terms of what people are supposed to do. 

This is the central question of Kushnir’s paper. The project began with Vlada Borgers, an undergraduate nutrition science student who brought an interest in children’s perceptions of healthy eating to Kushnir’s lab. Kushnir and collaborators Isobel A. Heck, currently with the University of Rochester, and Charlotte Borgers, Cornell University, connected that interest with research on children’s social and moral cognition. 

The researchers studied children between the ages of four and six. In an online sorting task, children categorized foods in three different ways: healthy or unhealthy, liked or disliked, and okay or not okay. The foods included relatively clear examples, such as broccoli and candy, as well as foods about which people might disagree. 

The children generally understood which foods were healthy and unhealthy, even at the youngest ages. They also continued to prefer foods such as candy over foods such as broccoli. The important developmental change was in the relationship between health and permissibility.  

“The four-year-olds didn’t think that ‘okay’, or ‘not okay’ had anything to do with ‘healthy,’” Kushnir says. Older children, she notes, were increasingly likely to say that unhealthy foods were also “not okay.” 

This reflects a broader pattern in children’s understanding of rules and choice. “When children think something is not okay, they also think it’s not a choice,” Kushnir says. 

For young children, “not okay” can mean more than “against the rules.” It can mean that the action is not available as a choice at all. If an adult says a child shouldn’t take someone else’s toy, a younger child may understand the rule as removing the possibility itself: the child simply cannot choose to take it. Older children are more likely to recognize that the action remains possible, but that choosing not to do it is the appropriate response. 

Kushnir’s earlier work suggests that children between roughly four and six undergo a significant shift in how they understand choice and self-control. Younger children may think that a person who strongly wants to do something must do it, or that a rule makes an action impossible rather than merely prohibited. As children develop greater self-regulation, they also become better able to understand that people can refrain from doing something even when they can and want to. 

Food appears to fit into that same framework. Children learn that some foods are healthy, that adults value healthy eating and that rules can constrain behavior. That structure may help children regulate their choices, but it may also create new opportunities for guilt or self-judgment. 

“They start to understand there are rules,” Kushnir says. “They understand that health has a lot to do with what the rules are, and that there are more opportunities for them to feel bad about their unhealthy choices because now they know that candy is ‘not okay.’” 

The study also included parent questionnaires about eating practices, including food restriction, control and shared meals. The reported patterns were consistent with the idea that the way adults organize food experiences matters.  

Greater parental restriction and control were associated with children viewing their food choices as needing to conform to standards, and with the idea that their own desires were not necessarily right. Shared meals and eating the same foods as children were associated with a more relaxed attitude toward contested foods. 

The researchers want to study how these ideas develop further, including among children with extreme picky eating or other eating-related difficulties. A planned follow-up study will also examine whether children judge other people’s moral character based on their food choices.  

How children understand changing their minds 

Where the first paper looks into children’s beliefs around food choices, the second looks into belief itself, asking whether children realize that people are less likely to change their minds about things they feel strongly about.  

The study is grounded in research on theory of mind: children’s developing understanding that other people have beliefs, desires, feelings and knowledge that may differ from their own.  

Adults often treat changing one’s mind as a sign of rationality: new evidence leads to new conclusions. But rationality doesn’t mean abandoning a belief whenever someone presents a tidbit of contrary information. Changing a strongly held belief should require stronger evidence than changing a weakly-held belief, Kushnir says.  

To test how children perceived this difference, Kushnir and her co-authors, Pearl Han Li, University of Wisconsin, and Laura Soter, University of York, presented children ages five to nine with short scenarios involving people who held either strong or weak beliefs. Children were asked whether the characters could change their minds and how difficult that change would be.  

In later tests, children were asked to consider what would happen after receiving evidence from several people who disagreed with the character’s original belief. The scenarios included factual, moral and preference-based beliefs. 

Even the youngest children were beginning to distinguish between strong and weak beliefs. By age nine, children clearly expected weak beliefs to be easier to change and strong beliefs to be more resistant. 

Children did not generally predict that evidence would completely overturn a belief. Instead, they tended to expect a weak belief to change somewhat and a strong belief to weaken while remaining in place. For Kushnir, that suggests children are already observing that people often hold on to what they believe to be true. 

“Children are very observant,” she said. “They understand that the beliefs you have are probably the beliefs you’ll keep.” 

The findings also raise questions about culture, and the kinds of evidence children view as persuasive. The researchers are replicating the study with children from different cultural backgrounds. Kushnir said that social evidence — being told by other people that you are wrong — may carry different implications in different cultures, depending on their emphasis on social harmony, conformity and independent thinking. 

Young thinkers 

Together, these studies add to a body of knowledge that shows how children’s social and moral concepts develop and tell us they are able to recognize the complexity of human behavior from a very young age. 

Ultimately, both papers point to the same larger lesson about childhood. “I don’t think people appreciate how sophisticated children are,” Kushnir says. “This research shows that they’re sophisticated learners and sophisticated thinkers, even on very different informational grounds than adults. This also means that, in a lot of ways, they can be more open-minded.”