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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.


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