At the beginning of the experiment, to explain the task, children and adults were asked to drink a
tiny little drop out of a conical plastic cup. By doing so, the participants were provided with an example
of a tilting angle with a cup of a different shape, and the goal of the task—to bring the water to the
rim—could be clarified. Then a glass was attached vertically to the shaft, and it was pointed out to the
participants that this glass was empty and could be turned around the shaft. A reference glass that was
actually filled with real water was positioned in front of the apparatus on the left-hand side. Children
and adults were asked to pretend that the glass on the shaft was filled with exactly the same amount
of water and to turn it so that this imaginary water would reach the rim of the glass but would not
spill. To help the children understand the task, a puppet was held next to the glass in the first practice
trial. Children were told to help the puppet drink a tiny little drop of water—just like they did before
with the plastic cup. After another practice trial without the puppet, the test trials were presented.
Neither in the practice trials nor in the test trials was a full glass ever tilted.