I remember reading about an experiment by psychologists on recovery time for hospital patients. In both conditions, a plant was placed in the patient's hospital room. In one condition, the hospital staff cared for the plant. In another condition, the patient was told they would have to care for the plant. The patients who were given the responsibility to care for the plant had better recovery rates.
Does someone know the citation for this study? I can't find it for the life of me!