Well… maybe not so simple
I have found that turning off lights in the day time when temperatures soar over 100 degrees outside makes a room seem cooler. There is still some light that leaks in from outside so it’s not completely dark.
While there is the mundane of light bulbs radiating heat it’s not the psychological effect that I write to herein.
There’s something about the dark that’s ineffable. It’s mysterious because we can’t see so well into it. The dark of the night can be comforting when we embrace the mysteries with our hearts.
When I read The Night Country by Loren Eiseley (see end notes) I fell into his contemplative prose and was enveloped by the mysteries of his night journey. Night and darkness were never the same again.
Darkness became mystery of infinite worlds… Perhaps this is the psychology of a darkened room in the daytime and at night as well…