Jean piaget showed children two identical beakers filled with the same amount of water. after the children agreed that both beakers held the same amount of water, piaget poured the water from one beaker into a taller, narrower beaker and then asked them about the amounts of water in each beaker. children in what stage would be unable to distinguish the fact that the beakers held the same amount of water?

The Swiss psychologist Jean Piaget (1896—1980), defined four stages of cognitive development.
Children in the preoperational stage would be unable to distinguish the fact that the beakers held the same amount of water. The preoperational stage  is the period from age two to seven. In this stage, children begin to use words as mental symbols and to form mental images.

The correct answer is the preoperational stage of cognitive development.

 According to Piaget's theory of cognitive development, children in the preoperational stage have not developed the ability of conservation. This means that children do not understand that the quantity of something remains the same despite changes to its arrangement or type of container it is placed in. In this instance, children did not understand that the quantity of water poured from a beaker to a taller, narrower one remained the same.