One study has shown that this act of kindness may have scientific foundations.
This particular study showed that people with a room overlooking a natural environment recovered quicker from surgery than those who looked out onto a brick wall. Though this may seem commonsense, if you are visiting a friend or relative in hospital take them a plant or flowers, especially if they have no window or if they are in a room with a window overlooking a wall or a barren area. Having a view of the natural environment may help speed up recovery and can induce positive emotion.
(Ulrich, 1983. 'A view through a window may influence recovery from surgery.' See research section for more details.)