Paoli, Pennsylvania, is a small town with a local suburban hospital. Patients at Paoli Memorial recover in a row of rooms facing a small courtyard. In the early 1980s, a researcher visited the hospital and gathered information about patients who had undergone gallbladder surgery between 1972 and 1981. Gallbladder surgery is routine and generally uncomplicated, but most patients in the 1970s recovered for a week or two before they returned home. Some took longer to recover than others, and the researcher wondered whether subtle differences between the hospital rooms might explain this discrepancy. Some of the rooms on one side of the hospital faced onto a brick wall, whereas others slightly farther down the corridor faced onto a small stand of deciduous trees. Apart from their differing views, the rooms were identical.
When the researcher looked at their recovery charts, he was struck by how much better the patients fared when their rooms looked out onto the trees rather than the brick wall. On average, those who faced the brick wall needed an extra day to recover before returning home. They were also far more depressed and experienced more pain. On average, their nurses recorded four negative notes per patient -- comments like "needs much encouragement" and "upset and crying" -- whereas those with a view of the trees warranted negative notes only once during their stay. Meanwhile, very few of the patients who looked out onto the trees required more than a single dose of strong painkillers during the middle part of their stay, whereas those facing the wall required two or even three doses. Apart from their view, the patients were very similar, and they had received identical treatment at the hospital. Each patient with a view of the trees was matched with a patient whose room looked out onto the brick wall, so that their age, gender, weight, status as smokers or nonsmokers, and attending doctors and nurses were controlled as tightly as possible. Since those factors were controlled, the only explanation was that patients who looked out at a stand of trees recovered more quickly because they were lucky enough to occupy rooms with a natural view.