Kids shrug off sunk-cost bias until about age 6, behavioral experiments reveal

Ever wonder why adults cling to things in which they've invested time or effort? In behavioral experiments, people often predict that they would stick with an option just because it was harder to get. Psychologists call this the sunk-cost bias—valuing a choice more because of past investment. Consider a classic example: Given two identical dinners—one expensive, one cheap—many people choose the expensive one to avoid "wasting" money.

But what about children? Do they share this same tendency to let past efforts dictate future choices? A new study in Journal of Experimental Psychology: General investigates this question, revealing a surprising difference in how young children approach decisions involving prior investment.

Testing children's sense of effort

To understand this developmental gap, researchers tested two competing ideas: Do children see past efforts as fundamentally irrelevant, or do they simply need a nudge to consider them? In a series of experiments involving 484 children ages 4 to 7, the team presented scenarios designed to mirror adult dilemmas.

In one key test, children heard a story about a girl who climbs two different hills to collect flowers. One hill is steep and difficult to climb, while the other is short and easy. Although the flowers she retrieves are identical, she is told she can keep only one. When asked to predict her choice, the results were striking. Unlike adults, who almost always choose the "hard-won" flower, the younger children chose between them at random.

To see if they could bridge this gap, the researchers introduced specific "prompts." Before making a prediction, some children were asked to think about the effort involved ("Which flower was harder to get?") or the potential for waste ("Which flower would be more of a waste to throw away?"). Others were asked a neutral control question about the size of the hills.

The results revealed a stubborn indifference in the youngest participants. For 4- and 5-year-olds, these hints made no difference. Even when explicitly prompted to consider how hard the girl worked, they continued to "respond at chance," picking between the flowers as if the past effort didn't exist. It seemed that for these early learners, the "sunk cost" simply wasn't a factor in the equation of choice.

A shift appears at age 6

What is most intriguing about the findings is that a change happens at age 6. While children under 6 showed indifference, those ages 6 to 7 changed their choices in response to the prompting questions. As the study shows, across all experiments, the clear question "Which takes more work?" made a difference in the choices of children ages 6 to 7 and encouraged them to opt for the more effort-requiring option, as adults do.

It also became clear that there are differences among types of "waste" prompts. When asked which object was "more of a waste to throw away," children ages 6 to 7 showed a tendency to select the high-effort object. It is possible to say that by age 6, children understand the idea of "underuse" as a form of waste: throwing away an item that required much effort to obtain.

It should be noted that an earlier prompt asking the children to choose which was more of a waste to get produced the opposite effect. Children tended to avoid high-effort objects.

In essence, these effort-related and specific waste-related prompts made older children's predictions more adult-like. They began to factor in past investments when making choices for others.

Learned, not built in

However, this emerging sensitivity was not absolute. As the authors carefully note, even among these older children, their choices "were not at the ceiling." This means that while prompting helped, a significant portion of 6- and 7-year-olds still didn't consistently choose the hard-earned option.

This nuanced finding leads the researchers to conclude that sunk costs "are not fundamental to conceptions of choice" in childhood. Instead, it implies that sensitivity to sunk costs is a learned behavior that emerges gradually, rather than an innate understanding.

With the help of scenario tasks involving effort-invested goods, the research provides important information about the development of the concept of the sunk-cost fallacy. Even though the experiment was conducted in specific contexts, the results indicate how crucial cultural learning and personal experience are to developing an understanding of this concept.

It is evident that children do not really take previous efforts into account when making decisions. This may help explain why children can abandon their actions or change them quite easily. Parents and teachers should keep in mind that it is better to encourage persistence by providing immediate reasons for it instead of talking about wasted efforts.