Is Your 4-Year-Old A Liar? Here's The Bright Side

Nov 2, 2015

Most parents bewail the inevitable occurrence of lying in their kids, but the emergence of deception in childhood may actually signal the development of something pretty wonderful: an ability to understand other people's beliefs as distinct from one's own.

This ability is part of what psychologists call "theory of mind," and a new paper finds that improving children's theory of mind abilities can turn honest 3-year-olds into strategic liars. That might not sound like a positive outcome, but it tells us something important about how theory of mind affects social behavior.

Before getting into the details, consider what a typical 3-year-old child does — and doesn't — already understand about other people's minds. By 18 months, children typically know that other people can have preferences that depart from their own. For example, in a study by Betty Repacholi and Alison Gopnik, young children saw an adult express a preference for broccoli over goldfish crackers. When the adult then asked for some of the food, 18-month-olds — but not 14-month-olds — handed over the broccoli, even though the child's own preference was presumably for the crackers. You can see a short demonstration of the experimental procedure here:

It isn't until age 4 or 5, though, that most children can pass the "false belief task," which is taken to reflect an understanding that other people's beliefs can depart from their own. In a classic version of this task, developed by Heinz Winner and Josef Perner, most 3-year-old children fail to appreciate that a character will expect an object to be where she last saw it, not where the child knows it to actually be. You can see a variant on a false belief task here:

Understanding that other people's beliefs can depart from one's own is a prerequisite for a host of sophisticated judgments and behaviors — not only moral judgments, as demonstrated at the end of the video above, but also for deception. Consider the task illustrated below, in which a child must deceive "Mean Monkey" to get the stickers he actually wants (watch minutes 7:12 to 10:04):

The strategic element here is transparent to adults: The child need only lie to Mean Monkey about the sticker he really wants, and Mean Monkey will choose the wrong sticker, leaving the child his first choice. Yet time after time, younger children fail to lie. This doesn't stem from an overwhelming desire to be good, but — at least in part — from a failure to appreciate that another's beliefs can diverge from reality and from one's own.

At least, that's what researchers had assumed. But it's hard to demonstrate a causal link between theory of mind and a behavior like telling lies — both emerge spontaneously in development and both are influenced by a variety of factors. Finding that one ability typically precedes the other, or that the abilities are correlated across children, is suggestive but ultimately falls short of demonstrating a causal connection.

That's where new research by Xiao Pan Ding and colleagues comes in. In a new paper published in the journal Psychological Science, the researchers report a study in which 3-year-old children were randomly assigned to one of two groups: a theory-of-mind training condition or a control group. In the theory-of-mind training condition, children participated in six sessions involving different theory of mind tasks, including versions of the false belief task described above. In the control group, children also participated in six sessions of training on developmentally appropriate tasks, but they weren't related to theory of mind.

By the end of the training, the children who received theory-of-mind training significantly outperformed their peers in the control condition on tasks that assessed theory of mind, like the false belief task above. They were also significantly more likely to lie.

To assess children's ability and propensity to lie, the children in the experiment completed a variant on the Mean Monkey task demonstrated above. They first played a simple game with the experimenter: The experimenter hid a candy in one of two cups and the child had to guess which cup contained the candy. If the child guessed correctly, the child could keep the candy. If the child guessed incorrectly, the experimenter could keep the candy. Having learned these basic rules, the child and the experimenter switched roles: The child now hid the candy and the experimenter had to choose a cup. If the experimenter chose correctly, the experimenter could keep the candy. If the experimenter guessed incorrectly, the child could keep the candy.

The experimenter dutifully closed her eyes while the child hid the candy but before choosing a cup, she asked the child: "Where did you hide the candy?"

To get the candy for himself, the child had only to lie — to mislead the experimenter into choosing the wrong cup. But on day one of the experiment, before undergoing any training, that's not what children did. Every 3-year-old who participated in the study instead told the experimenter the truth and the experimenter went on to select the cup with the candy, much to the child's dismay. Each child played the game with the experiments nine more times that day and, each time, the 3-year-old told the truth about where the candy was hidden, no matter that each time, the experimenter went on to select that cup. The 3-year-olds were unable or unwilling to strategically lie.

But two weeks later, after completing the theory-of-mind training or the control training, children had an opportunity to face off once again against the experimenter in the hiding game. And this time, the children who had completed the theory-of-mind training lied more than half the time. On average, they lied in about 6 of the 10 rounds of the game, whereas those in the control group lied in fewer than 2 of the 10 rounds. The theory-of-mind training paid off — not only on theory-of-mind tasks but also in strategic deception.

Turning children into liars may not seem like a laudable achievement, but it tells us something important about the relationship between theory of mind abilities and deception. Specifically, the design of the experiment supports a claim that goes beyond correlation: that a basic theory of mind is a prerequisite to verbal deception. Moreover, the findings support the broader idea that our understanding of our own and other people's minds has a causal impact on our social (or antisocial, as the case may be) behavior.

Of course, you're not so likely to cheer when you first find yourself the target of a lie, especially from your own child. Developing the ability to deceive is one thing; understanding whether and when it's appropriate is another — and that's likely to take quite a bit more than six sessions of training to work out.


Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo

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