Fun baby tricks #1: A-not-B Error

Around 5-6 months of age, infants begin looking for hidden objects. Around 7 months, they start to become much better at reaching reliably towards objects they want. Infants seem like they are on a steady march to become better and better at finding and grabbing objects. However, around 8-12 months, infants make a curious mistake. That brings us today’s blog post: the A-not-B Error.

Jean Piaget, the father of cognitive development, did most of his research on his three kids in the early 1900s. Although his theories are no longer in vogue, he is still revered today for the clever tasks he dreamed up for examining how young children think. The Piagetian search task is one of those simple clever tasks. Basically you have two hiding locations (we’ll call them location A and B) and you start off by showing the child that you are hiding a desirable toy in location A. After a pause (just a few seconds), you allow the child to search. Typically around 8-9 months of age, infants readily search in location A and retrieve the toy. Then with the child watching, you clearly hide the toy in location B. After a pause, you allow the child to search. That’s when you see it… the A-not-B error. See cogscibaby in action below!

At the time of the video, cogscibaby had just turned 9 months old.

The nice thing about this error is that it is pretty reliable! So grab a 9-10 month old near you and try this baby trick at home!

6 thoughts on “Fun baby tricks #1: A-not-B Error

  1. I seem to only see the photo. ? Does the “error” mean that they find the toy the first time under A successfully but curiously choose location B the second time? I’m dying to know!! haha.

  2. juliepark says:

    i love how he throws the cloth in disgust after the spoon isn’t under it. so cute!!!

  3. Mariru says:

    That’s so interesting! I never knew this!

  4. Dan Rindler says:

    I love the 2 videos you made for A not B error. I am a Feldenkrais practitioner who works with babies and I’m very interested in dynamic systems theory. I wrote a short blog post about A not B error for parents who I work with, and linked to your videos. I just wanted to share the link and say thank you for the videos!

    • cogscimom says:

      Thanks! I never knew about the Feldenkrais method but knowing dynamic systems, seems like a great instantiation of dynamic systems theory in real practice!

      • Dan Rindler says:

        Yes, Esther Thelen thought so, to the point that she enrolled in a 4 year training. I was a student in the first Feldenkrais class that she taught at IU. Here’s the letter that might interest you – a Feldenkrais practitioner (the late Mark Reese) sent her this letter, describing the method in dynamic systems terms after reading her and Linda Smith’s book. She went on to complete a training with him.

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