Answer:
Avery is in the preoperational stage of cognitive development.
Explanation:
According to Piaget's Cognitive Development Theory, Avery is still in the preoperational stage, which goes from 2-7 years of age.
This stage, as the name states, occurs before the child can formally carry on operations. During this time the child still thinks in a very concrete way, not being able to do this in a more abstract way and he/she struggles with logical thinking.
During this stage the child also struggles with constancy, which is the understanding that an object is still the same even if it changed its composition or was moved.
This can be explained through Avery's failure to understand that the water is the same, that there is no more and it was simply moved to a taller container which only gives the illusion that there is more of it.
