What experiment did the four sisters plan?

The March sisters all get pretty fed up with how much they have to work, especially Meg, who is a nanny for two little children, and Jo, who serves as a companion for Aunt March (a crotchety and often unpleasant older woman who really tries Jo's nerves). The girls decide to take a week and do no work whatsoever because they really want to give themselves a break. They rather enjoy themselves for a bit, but only so long as Hannah and Marmee are keeping the house going. When Marmee gives Hannah some time off and keeps to herself in her room, the girls discover how unpleasant it is to live in a dirty house with no dinner. Further, with all of their free time, they begin to appreciate free time less and less and forget parts of their routine. Poor Beth, for example, forgets to feed the bird, Pip, and he dies. In the end, the girls find that it is better to have time for work and time for play; the work time makes the play time feel that much more special, and the work time gives them a sense of accomplishment and satisfaction.