Ahh interesting. I am familiar with this effect though I don't understand the exact cause for it beyond the cake that you baked:) Perhaps I do have a bit of insight from a digital perspective. I have looked at my own work on a computer screen with some nice 3D glasses. To my surprise, white recedes and black comes forward. I wasn't cognitively engaged with this fact until I saw through the glasses, in fact I thought it was the opposite. White always seemed to push forward but it isn't how it actually functions. After seeing this effect, I noticed that many great artists, especially concept artists in the entertainment industries, use this trick to create great depth. You will see it over and over again in digital paintings, specifically environment paintings. A big bright sky with elements fading into light atmosphere and bold, blocky dark colors in the foreground. There must be something happening in the rods and cones of the eyeball that can be enhanced with the appropriate mixture. Its like our eyesight is tuned to perceive depth at its greatest degree under a sky lit by sun as we peer out of a forest.