Which Would Be a Good Way to Test Working Memory

Which would be a good way to test working memory span?

A) Present a child with seven numbers and test to see if the child remembers the seven items after 30 minutes.
B) Have a child memorize a set of objects in a certain order and test to see if they can recall them in the opposite order after they succeed.
C) Have a child memorize different types of objects (e.g., animals, vehicles, or fruit) and test to see how the child chunks the items in memory.
D) Show a child sets of five objects for 20 seconds and test if they can recall all the objects.
E) Read off a list of objects and test to determine the largest set of objects the child can recall correctly.