- A-not-B error
A-not-B error (also known as "stage 4 error" or "perseverative error") is a phenomenon uncovered by the work of
Jean Piaget in histheory of cognitive development of children. The A-not-B error is a particular error made by young children during substage 4 of theirsensorimotor stage .A typical task goes like this: An experimenter hides an attractive toy under box "A" within the baby's reach. The baby searches for the toy, looks under box "A", and finds the toy. This activity is usually repeated several times (always with the researcher hiding the toy under box "A"). Then, in the critical trial, the experimenter moves the toy under box "B", also within easy reach of the baby. Babies of 10-months or younger typically make the perseverance error, meaning they look under box "A" even though they saw the researcher move the toy under box "B", and box "B" is just as easy to reach. This demonstrates a lack of, or incomplete,
schema ofobject permanence . Children of 12-months or older typically do not make this error.Competing explanations
Traditionally, this phenomenon has been explained as the child seeing an image and remembering where it was, rather than where it is. Other accounts deal with the development of planning, reaching, and deciding things. There are also
behaviorist accounts that explain the behavior in terms of reinforcement. This account argues that the repeated trials with hiding the toy in box "A" is reinforcing that specific behavior, so that the child still reaches for box "A" because the action has been reinforced before. However, this account does not explain the shift in behavior that occurs around 12-months.
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