Suppose Sabine, a six-month-old baby, fails to realize that her crib mobile continues to exist when she is not looking at it. Describe how Sabine's thinking on this issue might change as she progresses through the three stages of equilibration

What will be an ideal response?

Students' answer to this question should focus on the progression through the three stages from (1) stability of thinking to (2) instability of thinking to (3) stability of thinking. To receive full credit, students should note that the final stage of equilibration is even more stable than the initial stage. The following is an example of a good answer: In the first stage, Sabine is stable and satisfied. She doesn't think of the mobile at all unless it is in her field of vision—out of sight, out of mind. One day when she is playing in her crib, she may look at the mobile, turn her head away from the mobile, and then look at the mobile again. At this point, she may notice that the mobile is still in the same spot when she looks away and then looks back again. As a result, she may enter the second stage, a state of disequilibria in which she thinks of the mobile when it is out of sight, but questions whether or not it still exists when she can't see it. After some investigation, she will enter the third stage as she develops a mental representation of the mobile and realize that it continues to exist even when it is out of sight. This way of thinking will be more stable than her original way of thinking because further observations will not call it into question (i.e., the mobile will remain constant every time she looks away and then back again).