Piaget was convinced that the mind of a child develops due to psychosocial conflict resolution. develops through a series of stages. is like a blank slate at birth. is not heavily influenced by maturation. is heavily dependent on the child's personality.

develops through a series of stages.  

Explanation:

Jean Piaget was a psychologist who developed a theory on cognitive development according to which our cognitive development goes through different stages since childbirth (according to him since birth we already have some development via our senses) and until adolescence/adulthood and in each stage our way of thinking and reasoning becomes more complex and logical.

These stages happen thanks to the maturation of the brain and it allows us to go through an "upper" stage and it doesn't depend on the child's personality but rather on brain development.

Thus, Piaget was was convinced that the mind of a child develops through a series of stages

i believe the answer is:   psychological  experiment

in this experiment, wilhelm wundt became the first person that implement scientific method in analyzing the pyschological phenomenon.

due to this result, wilhelm wundt also able to make psychology to be acknowledged as a separate scientific field from biology.

haile selassie i was the emperor of ethiopia from 1930-1974