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Toddlers May Be Able to Determine Whether Adults Are Lying


Though scientists have generally thought children start to discern intentional falsehoods around the age of four, a new study suggests that may happen even earlier. Mordolff/Getty Images
Though scientists have generally thought children start to discern intentional falsehoods around the age of four, a new study suggests that may happen even earlier. Mordolff/Getty Images

Toddlers have a lot on their plates. Not only do they have to learn to talk, use the toilet, and eat with a fork, they also have to figure out why people do what they do. Good luck to them.

But new research published in the Proceedings of the National Academy of Sciences suggests that children begin figuring out what the deal is with people much earlier than previously thought. The study focused on determining at what age children begin to understand that other people can be mistaken, or can hold false beliefs about the world. Until recently, researchers believed children began putting all this together around the age of 4, regardless of where in the world they live. But this study shows that toddlers as young as 2-and-a-half can recognize when somebody's being lied to — as long as the test is simple enough.

The classic way developmental psychologists have tested whether children understand false beliefs involves telling the child a story about somebody who holds a false belief, and asking her to predict what the person will do next. In the study, for instance, a character named Sally puts her toy in one of two containers on the table, and leaves the room, but while she's gone, someone comes in and moves the toy into the other container. Children are asked to predict which container Sally will check the next time she wants to play with her toy.

"Prior to age four or so, children answer this question incorrectly," says study co-author Rose Scott, assistant professor at the University of California Merced. "They say that Sally will look for the toy where it actually is, suggesting that they don't understand that Sally has a false belief about the toy's location. This led many researchers to think that it isn't until at least age four that children realize that other people can have thoughts and beliefs that differ from their own."

However, research conducted over the past 10 years suggests that babies as young as six months old show some signs of understanding of the concept of false belief, as long as the test is simple enough, suggesting that toddlers understand more than the test results let on. The narrative of Sally and her toy might not seem very complicated to you, but that's because you're somebody who could probably follow the plot of a season of "Game of Thrones." (Maybe.) For a toddler, the story of Sally and her toy might be harder to follow than a David Lynch movie.

This finding inspired Scott and her co-authors from the U.S. and Singapore to adapt the story of Sally and her toy for younger audiences, like so: Sally leaves her toy in her room. Somebody comes and takes the toy to an undisclosed location. Where will Sally look for her toy?

The researchers gave 140 individual 2-and-a-half year olds from the U.S. the task of correctly predicting where Sally will look for the toy based on the information given in the edited story, as told interspersed with some clarifying questions to make sure the children were understanding the story each step of the way. With these two, simple changes to the story, the task could be completed by kids as young as 2-and-a-half years old, suggesting that the ability to realize other people can have different thoughts and beliefs develops much earlier than was traditionally thought.

"Our results have implications for theories of how the understanding of other minds develops." say Scott. "According to some researchers, the ability to understand others' mental states does not emerge until the early school years: at around age four, children undergo a radical change in their understanding of other people, and this is why they begin to pass traditional false-belief tasks. The fact that children pass our task much earlier suggests that we have been underestimating children. Rather than undergoing a radical change at age four, children may possess an understanding of belief early in life — perhaps in infancy — and they gradually become better at using this understanding in a variety of social situations."



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