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Think twice (19-22 months)

**How children update their mental representation of an object**

Many studies have looked at how children learn about the world from what they observe, but how do children come to learn from what others tell them?  Going one step further, when does the ability to learn new information about objects that aren’t even present emerge? This would involve bringing to mind a mental representation of the object and incorporating the new information into your understanding of, for example, what it looks like.  Researchers examined this question in a study that looked at the emergence of young children’s ability to update their mental representations of an object based on information given by an adult when the object was in another room (Ganea et al. 2007).   The two ages examined, 19 and 22 months, span the time when this ability comes online.


  • Two identical stuffed animals (e.g., two green frogs)
  • One different stuffed animal (e.g., one pink pig) to be a distractor
  • One bucket of water
  • Three aluminum trays
  • A confederate


Start by showing the child the three stuffed animals and introduce one of the two identical ones with a proper name (e.g., Lucy). Show the child the other identical toy but do not name it and then set it aside. Finally introduce the different toy as a friend and then allow the child a few minutes to play with the named toy and the different, distractor toy.  Check that the child learned the name for the target animal (e.g., by putting them both down and asking the child to “get Lucy”).

Then put the three animals away (e.g., in a basket) and leave the room with the child.  While looking at a book with the child, the confederate should enter carrying a bucket of water and say that she planned to wash something (e.g., a table) in the other room (where the toys are).  After 2 minutes, the confederate should return and say: “I’m so sorry! I was washing the table, and I spilled water all over Lucy. Lucy is wet now! She’s covered with water” (Ganea et al., p. 736).  You can then say to the child, “Oh no, did you hear that? Lucy got wet! She’s all covered in water. Do you want to go see Lucy? Let’s go see Lucy!”

In the test phase, when the child re-enters the first room, she will see the three stuffed animals on the three trays.  One of the identical toys and the different, distractor toy should be wet.  The trays should be arranged such that the different wet toy is on its tray between the trays with the wet target toy and the dry identical toy.  Ask the child to show the target animal: “Which one is Lucy? Show me Lucy.”

Notes & Observations

What did you observe? Which toy did your child choose? The child should choose the wet target toy if she has updated her mental representation from the information given by the confederate. However, she might choose the dry identical toy if she had not updated her representation of “Lucy” or the different wet toy if she was just interested in a wet toy.

Research Findings & Extension

The researchers found that 22-month-olds reliably chose the wet target animal greater than chance whereas 19-month-old children seemed to choose randomly between the wet and dry versions of the stuffed animal. Thus, children’s ability to update a mental representation of an object with new information that they hear about but don’t see happen emerges around this age.  This capability opens the doors for learning all sorts of information indirectly and remembering it going forward.


Ganea, P. A., Shutts, K., Spelke, E., & DeLoache, J, S. (2007). Thinking of things unseen: Infants’ use of language to update object representations. Psychological Science, 18(8), 734-739.

Listen Up! (24 months)

**How young children learn new words through overhearing**

Have you ever wondered how kids pick up so many words that you never used when talking to them? Words that you may want them to learn or not J. Not all cultures speak directly to their children as much as American mothers, so there must be other mechanisms through which children learn language. Researchers have examined this in toddlers to see how kids learn new words by overhearing them while playing with a toy.


  • A confederate, i.e., a friend you can talk to so that the child has a conversation to overhear
  • Four unfamiliar objects, that is, objects that you know your child does not know how to label.  In the study they used: a wallpaper roller, a noisemaker, an oddly shaped yo-yo, a small wooden toy made of two connected disks, etc.
  • A bucket that the four objects fit in
  • One nonsense word: dax
  • A toy to distract the child. In the study, they used a pop-up toy like this one so that it required the child’s attention to manipulate it.

pop-up dinosaur


For the scenario, set the child with the toy about 1 meter away from where you and the confederate will play a game.  Tell the child that he is waiting his turn.  Do not make eye contact with the child as you go through the objects one by one with the confederate.

Choose one of the objects to be the target object. You will pull that one out of the bucket second and will introduce it with the nonsense word.  While the child is playing with the toy nearby, go through the following dialogue (in an excited voice) with the confederate three times:

– Say “I’m going to show you what’s in here. Want to see what’s in here? I’ll show you what’s in here.”  Pull the first object out of the bucket. Let the confederate hold it and then put it back in the bucket.

– Say “I’m going to show you the dax. Want to see the dax? I’m going to show you the dax.” Pull the target object out of the bucket. Let the confederate hold it and then put it back in the bucket.

– Say “I’m going to show you what’s in here. Want to see what’s in here? I’ll show you what’s in here.”  Pull the third object out of the bucket. Let the confederate hold it and then put it back in the bucket.

– Say “I’m going to show you what’s in here. Want to see what’s in here? I’ll show you what’s in here.”  Pull the fourth object out of the bucket. Let the confederate hold it and then put it back in the bucket.

After going through this object-finding routine three times, you do one round of this with the child, but do not give the nonsense word when you take the target object out of the bucket; just introduce it in the same way as the other objects.

Then, during the comprehension phase, place all four of the objects in random positions on a tray and ask the child to show you the dax.

Notes & Observations

What did you observe?  Was your child engaged with the toy? Did your child learn the new word through overhearing despite being distracted?

Research Findings & Extension

The researchers found that 24-month-old children could reliably choose the target object when asked to show them the “dax”.  They also ran a condition of the study where children were not given a toy to distract them and they learned the new word through overhearing equally in both scenarios.  The researchers analyzed videotapes of the research sessions to track the children’s attention during the task, and interestingly, the children tended to shift their attention to the adults’ conversation when they heard an unfamiliar word used before the target object was shown. This suggests that children are actively trying to gather information, such as mapping new words to objects.  The findings inform us about how children learn outside of direct conversation.


Akhtar, N. (2005). The robustness of learning through overhearing. Developmental Science, 8, 199-209.

Baby See, Baby Do (newborn)

**How newborns imitate others’ facial expressions**

Many studies have shown that imitation is an important social mechanism. But when are babies able to imitate others around them?  Are they born with any innate ability to engage in this social exchange? In a study that might sound familiar from Psych 101, Meltzoff and Moore (1977) systematically tested whether newborns who were 12-21 days old imitated facial expressions that they saw.


  • You!


Start by looking at the baby with a neutral “passive” face.  Then when the baby is looking, make one of the following gestures four times in about 15 seconds (see image from the original 1977 article). Resume a passive face and see how the baby responds.  Try all five gestures:

–       Lip protrusion

–       Mouth opening

–       Tongue protrusion

–       Sequential finger movement (opening and closing the hand by serially moving he fingers)

–       Head movement in a clockwise motion

meltzoff2 imitation

Notes & Observations

What did you observe? Did your child imitate any of the gestures?

Research Findings & Extension

The study showed that newborns did instinctively respond by consistently imitating the specific facial and manual gestures that they saw. A follow-up study showed the same response in infants only hours old!  This is remarkable because it shows imitation behavior far earlier than it was originally thought to start at 8-12 months. The authors explained the phenomenon as a result of the infant’s primitive ability to “represent human movement patterns they see and ones they perform using the same internal code” (Meltzoff & Moore, 1989, p. 961). This tendency does seem to fade by 2-3 months, possibly because babies can communicate more intentionally by that time.


Meltzoff, A.N. & Moore, M.K. (1977). Imitation of facial and manual gestures by human neonates. Science, 198, 75-78.

Meltzoff, A.N., Moore, M.K. (1989). Imitation in newborn infants: Exploring the range of gestures imitated and the underlying mechanisms. Developmental Psychology, 25, 954–962.

Yours, Mine, and Ours (2-3 years)

**How children develop an understanding of ownership**

Anecdotally, we have all seen that children can be possessive with their objects.  But knowledge of who owns an object is not obvious from looking at it, so how and when do children come to know that something belongs to them versus someone else? How do they keep track of an object’s history and discriminate their object from other similar objects? Researchers have started to look at this question with clever experiments with 2 and 3 year olds that disentangle which factors children pay attention to when determining ownership (Gelman, Manczak & Noles, 2012).


  • Set 1: a set of three different objects, but from the same category (e.g., three different looking car, animal, or food toys)
  • Set 2: a set of three objects that are identical (e.g., three of the same toy cars, animals, or foods)
  • Set 3: a set of three objects, two of which are from the same category (e.g., two different cars) and one object which is plain and undesirable (e.g, a piece of Styrofoam or cardboard)
  • A tray to place the three objects on during the question phase


Sit at a table with the child with the objects out of view.

Trial 1:  Start with the objects from Set 1, which you will take out one at a time. For this set, it does not matter which of the three objects are assigned to you or the child. For the labeling phase, bring out the first object and say “This is yours; this is for [child’s name],” and put it in front of the child.  Then, bring out the second object, show it to the child, and say, “This is mine; this is for [your name],” and place it in front of yourself.  Finally, bring out the third object, hold it up to show the child, and say, “See this; look at this,” and then place it on the table equidistant from the other two objects.  For the question phase, take the three objects and place them on a tray in the order that they were first presented as the child watches.  Then ask: (a) “Which one is yours?” and (b) “Which one is mine?” and note whether the child picks the correct objects for the two questions.

Trial 2:  Follow the above procedure with the objects from Set 2 and note the responses. For this set, it does not matter which of the three objects are assigned to you or the child since they are identical.

Trial 3: Follow the above procedure with the objects from Set 3 and note the responses. For this set, be sure to assign the plain object to the child.

Notes & Observations

What did you observe? Did your child keep track of which object he was assigned for each set of objects?  Were any of the sets easier or harder?

Research Findings & Extension

The results of the study were different based on the age of the child and the make-up of the set of objects.  Both 2 and 3 year olds were good at the task with varied sets of objects like Set 1, meaning that they kept track of them and correctly answered the questions about which object was assigned to themselves and the researcher.  The set of identical object was more difficult for the 2 year olds but the 3 years did well on this task, meaning that they tracked their object “through space and time” using the information they were told – even though all three objects looked exactly the same. Although the researchers didn’t try this, it would be fun to see just how good children are at tracking their object visually, Three-Card Monte style J Finally, the set where the child gets the plain object was hardest for the 2 year olds who actually did a better job of keeping track of the researcher’s more interesting object than their own. The researchers also looked at a phenomenon called the “endowment effect” where people tend to like something more just because they own it – there’s a lot more to study about ownership, but it’s clearly an understanding that takes root early on.


Gelman, S., Manczak, E., & Noles, N. (2012). The nonobvious basis of ownership: Preschool children trace the history and value of owned objects.  Child Development, 83, 1731-1747.

Fitting In (18-24 months)

**How children make errors when judging the size of objects they interact with**

Have you ever seen a two-year-old trying to get his hands or feet into something way too small for him?  Not pretending, but seriously and persistently trying, say, to fit into a toy car that would be impossible to get into?  Well, you’re not alone.  Dr. Judy DeLoache and her colleagues noticed the same phenomenon in young toddlers and decided to study what they called “scale errors.” Because these occurrences are infrequently spotted in everyday life, they created a lab situation that would make children’s errors in judging the scale of objects more likely (of course, they still don’t always occur!).  Setting this one up at home would be a commitment, but the errors are really interesting to witness.


  • Large (appropriate for a child to actually get into) and small (not miniscule, about doll house-sized) versions of the same object.  For example, the original study used a Little Tikes Cozy Coupe ® car and a small toy version of it (which also had movable parts).  A chair, slide, or wagon could also be used.  The two objects should look as identical as possible.
  • A confederate


Have the child come into the room where the large object (and little else, if possible) is located and let him play with it as he normally would for 5-10 minutes. Then take the child out of the room and have your friend replace the large toy with the smaller replica, placing it in the same location and removing the large toy from the room. Do this without the child seeing and without mentioning anything about the change.

When you bring the child back into the room, do not comment on the change even if your child reacts.  Let him explore on his own, or if he is hesitant, perhaps suggest that he play with the toy.  Watch carefully to see if your child has a momentary lapse in understanding how to interact with the object.

Notes & Observations

What did you notice? How did your child react?  Did he try to perform any of the same actions with the small object as he did with the large object?

Take a look at some clips from the DeLoache lab of children making a scale error with the small objects:

Research Findings

DeLoache et al. (2004) found that 18 to 20 month-olds are most likely to make this kind of mistake. By 24 months, children hardly ever make these kinds of errors. Psychologists believe that when children display this sort of behavior, it indicates a time in their development when their action planning is misguided. In the case of this phenomenon, the children are thinking of the larger version of the object when they are planning how they will act on the smaller version.  Even if you can’t re-create the study, many people report children doing this spontaneously, so keep an eye out!


DeLoache, J.S., Uttal, D.H., & Rosengren, K. S. (2004).  Scale errors offer evidence for a perception-action dissociation early in life. Science, 304, 1047-1029.

Every Little Bit Helps (18 months)

**How children have altruistic intentions**

Will young children help others reach a goal?  Are humans the only species that would do so without any immediate benefit?  Researchers at the Max Planck Institute of Evolutionary Anthropology in Germany studied these questions in 18-month-old children and young chimpanzees (Warneken & Tomasello, 2006).  They created scenarios where the researcher needed help: either he could not reach an object, could not access something easily, or made a mistake of some sort.  In each situation, there was a point at which the child or chimpanzee could help the researcher fulfill his intention.


  • A confederate (e.g., a family friend) who can act the part

The authors posted supplementary material for the study, including adorable videos of children and chimpanzees doing the tasks, on Science’s website:

The materials for this study were very simple in most cases.  See video S1 for an example of an “out-of-reach” problem, where the adult accidentally drops a clothespin on the floor and unsuccessfully reaches for it.  See video S2 for an example of a “physical obstacle” problem where the adult wants to put magazines in a cabinet but the doors are closed so he bumps into it. See video S3 for an example of a “wrong result” problem where a book slips off of a stack as the adult tries to place it on top of the stack.  Note that for the scenarios you re-create, your child should be able to manipulate the materials used (e.g., if you try the cabinet scenario, your child should be capable of opening the cabinet doors).


Ask the confederate to act out each scenario, as in the video. After the “problem” occurs, the adult should look at the problematic object for 10 seconds, allowing time for the child to intervene.  After 10 seconds, the adult should alternate gaze between the object and the child for another 10 seconds.  Importantly, if the child helps, he should not receive any praise or benefit for helping before the next scenario occur

Notes & Observations

What did you observe? Did your child realize that the adult needed help in each scenario?  Were some scenarios harder than others?

Research Findings & Extension

For each scenario where the adult needed help, the researchers also tried a “control” version (with different children) where the adult acted intentionally instead of accidentally.  So, instead of accidentally dropping a clothespin, the adult intentionally threw the clothespin on the floor.  The results showed that children helped significantly more in the “accidental” action conditions than in the “intentional” conditions – that is, children helped when the adult actually seemed to need help and furthermore, did so within about 5 seconds of seeing that there was a need!  Similar tasks with chimpanzees showed that they also helped, but only did so reliably in the “out-of-reach” scenarios in which the adult’s intention may have been easier for them to understand.  This evidence of helping in chimpanzees differed from previous studies, possibly because it used non-food objects and involved chimpanzees helping humans rather than other chimps.  Regardless, the results of both the primates and very young children (too young to have been trained in helping) suggest an altruistic nature that is evolutionarily unusual.


Warneken, F. & Tomasello, M. (2006). Altruistic helping in human infants and young chimpanzees.  Science, 311, 1301-1303.

Pick This, Not That (30-36 months)

**How children use rules to learn the meanings of new words**

 How can children learn new words so quickly?  Do they have some way to match new objects to new words that they hear and will they resist giving an object two names?  Many psychologists have studied what they call the “mutual exclusivity” bias where children learning new words avoid giving an object they already know another name and instead assign a new name to a novel object.  Below I describe one of the first studies to show this learning mechanism: Markman & Wachtel (1988).


  •  Six familiar objects, that is, objects that you know your child knows how to label. In the study they used: a banana, a plate, a cup, a spoon, etc.
  •  Six unfamiliar objects, that is, objects that you know your child does not know how to label.  In the study they used: a cherry pitter, a lemon wedgepress, tongs, an odd shaped container, etc.
  •  Six nonsense words.  Researchers use a variety of words that are novel to children to test out their theories of word learning.  For example, you can use:  fep, bleen, dorn, febbit, blick, and plog.


Sit on the floor across from the child.  Tell the child, “I’m going to show you some things and ask you to pick some. Listen carefully and give the best answer you can.”  Place a pair of one familiar object and one unfamiliar object in front of the child.  Ask him to “Show me the X” using one of the nonsense words from your list and record which object your child picks.  Do not provide any feedback.  Continue this process with the next five pairs of familiar and unfamiliar objects, using a different nonsense word for each pair.

Notes & Observations

What did you observe? Did your child pick the novel object when you asked to see the “fep” or other novel word?  What do you think he would have done if you said “show me one”?

Research Findings & Extension

The researchers found that when asked to pick the object referred to by the nonsense word, children picked the unfamiliar object on almost 5 out of 6 trials.  This was more often than expected by chance; in contrast, they chose randomly in the condition where the researchers asked the children to “show me one.”  Thus, the children were not just gravitating toward the unfamiliar object; the presence of the novel word compelled them to pick the novel object.  The paper goes on to test many different variations, including how children attribute novel words to parts of objects.  Others have looked at bilingual children and how they suspend this bias, since they, of course, need to assign two words to each object, one in each language.


Markman, E.M. & Wachtel, G.F. (1988).  Children’s use of mutual exclusivity to constrain the meanings of words.  Cognitive Psychology, 20, 121-157.

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.