What was the primary object used in Piaget's famous conservation task study?

The primary object used in Piaget's famous conservation task study was identical beakers of liquid. This task was designed to assess children's understanding of the concept of conservation, which refers to the ability to recognize that certain properties of objects, such as volume, mass, or number, remain the same despite changes in the objects' form or arrangement.

In the classic example of the conservation task, children are presented with two identical beakers filled with the same amount of liquid. When one beaker is poured into a taller, narrower beaker, the child is asked whether the amount of liquid is the same in both beakers. Younger children, typically in the preoperational stage, often fail to understand that the amount remains constant, demonstrating their cognitive limitations at that developmental stage. This study provided insight into the cognitive development of children as they grow and the processes by which they begin to understand more complex concepts of conservation.