Seven-Year-Old Marvin and Four-Year-Old Edgar Are Sitting at the Table

Multiple Choice

Seven-year-old Marvin and four-year-old Edgar are sitting at the table as their mother pours milk into their glasses.Both glasses are the same size and shape.However,Marvin's mother notices a chip on the lip of his glass,and decides that it is safer if she pours that milk into another glass.The new glass is shorter and much wider,and when she pours the milk into the new glass Edgar laughs and says that now he has more milk than Marvin.However,Marvin is not upset because he knows that he still got the same amount of milk.Which Piagetian principle is Marvin demonstrating?

A) formal operations
B) decentering
C) the preoperational stage
D) the abstract operational stage