A German study conducted a couple of years ago found that people came up with more creative ideas in a dark environment than in one flooded with light. The researchers theorized that the darkness reduces inhibitions and provides a feeling of freedom.
Maybe this is connected to the fact that so many writers are most productive at night--although the reduction in the number of distractions during that time probably also has a lot to do with it.
It might be worth experimenting with different light levels when you're doing creative work to see whether this works for you.
