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A Trusted Agent (3 years)

**How children strongly trust what people tell them**

Can children resist the urge to trust what adults tell them?  When can they suspend belief in others and change their behavior accordingly?  Jaswal et al. (2010) examined whether children have a strong inclination to believe what others tell them.  In the study, the researchers had children participate in different conditions which, when compared, tested their hypotheses.  Below, I’ll describe the mechanisms of the “testimony” condition which shows the strong effect of children’s trust in spoken testimony when searching for something desirable: a sticker.


  •  8 stickers
  •  Two plastic cups of different colors (e.g., red and blue) that the stickers can be hidden beneath
  •  A tray where the cups can be placed upside-down
  •  A piece of cardboard large enough to conceal your hands while hiding stickers under the cups but not so large that your shoulders and face are concealed
  •  A confederate (e.g., a family friend) who can provide the testimony


Ask the confederate to sit at a table across from the child.  Start by explaining to the child that she’s going to play a game where she tries to find a sticker hidden under the cups.  If the child finds the sticker in the first cup she looks under, she gets to keep it – otherwise the confederate does.  He also tells the child, “I’m going to try to get as many stickers as I can! How about you?”

Start by placing the two cups on opposite ends of the tray and then position the cardboard screen to hide the confederate’s hands as he places the first sticker under one of the cups behind it.  He then lifts the screen and says that the sticker is hidden in the cup opposite to where it’s actually hidden; if it’s under the blue cup, he says:  “it’s in the red cup.” Next, push the tray toward the child and allow her to search under one cup. If she chooses the cup that was indicated, the incorrect cup, she will not find the sticker and the confederate can show her where it is and then keep it. If she chooses the correct cup, she can keep the sticker she finds.

This game continues for 8 trials; mix up whether the sticker is actually on the right or left so that it’s balanced. You can keep track of which cup the child chooses each time. Don’t worry, the child can have all of the stickers at the end (and even one occasionally during the game if he’s getting frustrated!).

Notes & Observations

What did you observe? Did your child search under the indicated cup the first time?  What about the subsequent trials?  Did he come to a realization about your “trickiness” and change course?

Research Findings & Extension

The researchers found that, naturally, all children looked under the cup that was indicated (“it’s in the red cup”) on the first trial.  Surprisingly though, children did not quickly realize that they should not trust what the experimenter said – many children did not find a single sticker over 8 trials!  In the study, a second condition was used called the “arrow” condition where the adult indicated which cup held the sticker by placing an arrow on it (children were trained to use this as a cue) but did not say anything.  In contrast, in that condition, children quickly realized that they should not trust the arrow’s location and found many more stickers.  The researchers argued that children’s belief in verbal testimony is so entrenched that it is difficult for them to inhibit responding to it (whereas they are not accustomed to trusting the arrow).  This sort of trust in the adults around them would be adaptive for infants and children since they have no other source for helpful information and would become stronger over time as it’s reinforced. By age 4, children do not show this same persistent trust.


Jaswal, V.K., Croft, A.C., Setia, A.R., & Cole, C.A. (2010). Young children have a specific, highly robust bias to trust testimony. Psychological Science, 21, 1541-1547.


Now You See It, Now You Don’t (10-12 months)

**How children make errors when searching for an object**

Do babies know that an object still exists after it’s no longer visible?  Can they find something that’s been hidden in plain sight?  These are some of the questions brought up by Piaget’s (1954) classic demonstration of the “A-not-B error.”  In this phenomenon, children make what is called a perseverative error where they continue to search for an object in location A even after it has been hidden in location B right in front of them!


  •  Two identical opaque containers placed on a piece of cardboard about 1.5 feet apart
  •  A small unfamiliar toy that can be hidden


Sit on the floor across from the child, who can be seated in someone’s lap to hold her until it is time to search. Place the two identical containers upside down on the cardboard, slightly out of the child’s reach.  Establish eye contact with the baby and get her attention, showing her the toy and telling her to “look here” as you hide it under one of the two containers, which is your location A.  You can shift your gaze between the object and location A as an indication of where it is hidden, but do not say where it is.  Now wait 4 seconds and then push the cardboard toward the child so that the containers are at an equal distance and observe where she first searches for the toy.  Do not provide feedback regardless of whether she chooses the right or wrong location.

Repeat this procedure hiding at location A 3 more times. Most infants should be able to accurately find the toy during these trials.  Now on the fifth trial, you will follow the same procedure, except that you will place the toy under the second container, location B.  Observe where the baby searches.  Repeat this for two more trials and see whether she continues to search in location A or changes to location B.

Notes & Observations

What did you observe? Did your child continue to search in location A even after you had switched to B?  How many times did she make the perseverative error?

Research Findings & Extension

Many researchers have found that babies between 10-12 months continue to search in location A even after they have watched the experimenter place the object in location B.  This error has been attributed to infants’ inability to stop themselves from searching in a place where they were rewarded with finding the toy or their inability to maintain the short-term memory of the new location.

However, Topal et al (2008) published a study suggesting that some of the source of the error comes from infants over-interpreting the communication signals given by the adult (such as eye contact and verbal attention-getting). They implemented a stripped-down procedure where the experimenter faced to the side and did not communicate with the child in any way but did everything else in terms of hiding the objects exactly the same way.  They found that the rate of the error was much less in this condition since it no longer seemed like the adult was trying to “teach” anything.  Try this version a few weeks later (with different containers and toy) and see if your infant makes fewer errors.  You can also try the procedure after 12 months and see if the error is no longer made at all.


Piaget, J., (1954). The construction of reality in the child. New York: Basic Books.

Topal, J., Gergely, G., Miklosi, A., Erdohegyi, A., & Csibra, G. (2008). Infants’ perseverative search errors are induced by pragmatic misinterpretation. Science, 321, 1831-1834.