[This post was originally published in September, 2007]
Here’s a task that four-year-olds can do but three-year-olds have some trouble with. Imagine Sally in the picture below is playing with a ball. She puts the ball in the box and goes to the kitchen to get a drink. While she’s gone, Bill takes the ball out of the box and puts it in the bucket. When Sally returns, where does she look for the ball?
Most three-year-olds will say Sally would look in the bucket, apparently failing to realize that Sally doesn’t know anything about what Bill did while she was gone. Some researchers have explained this phenomenon by speculating that young children haven’t yet formed a theory of mind; they don’t understand that other people can have thoughts independent of their own.
But Susan Birch and Paul Bloom believe they have found a scenario where adults make a similar error.
This is Sally. She finishes playing with the ball and puts it in the box. Then she goes outside to play. While Sally is outside playing, her sister Denise moves the ball to another container. Then, Denise rearranges the containers in the room until they look like the picture below.
When Sally returns, she wants to play with the ball again. What are the chances Sally will look first for her ball in each of the above containers?
Here is how the adults given this test responded, as you might expect:
Another group of adults was shown the same set of pictures, but with a key difference in the text. this time they were told that “Denise moves the ball to the bucket.” The remainder of the instructions were the same. Now look at the results:
This time significantly more people said Sally would look for the ball in the bucket — despite the fact that Sally had the same information in each scenario. Birch and Bloom call this phenomenon the curse of knowledge — now that they know the ball is in the bucket, even adult respondents are more likely to say Sally will look there for it.
Birch and Bloom are careful to point out that this study doesn’t disprove the notion that three-year-olds are unable to take the perspective of others, but it does make it clear that other factors are in play. And it’s possible that, rather than being unable to understand the thoughts of others, younger children are simply more susceptible to the curse of knowledge.
Birch, S., & Bloom, P. (2007). The Curse of Knowledge in Reasoning About False Beliefs Psychological Science, 18 (5), 382-386 DOI: 10.1111/j.1467-9280.2007.01909.x