Maya lights are not like real lights. This is especially true for lights with a negative intensity value. Negative intensity values act like mini-black holes, actually removing light from a scene. This can be handy for enhancing mood or appearance by darkening areas that would otherwise be lighted. This example shows a -1 intensity point light in the corner of the room compared to the same scene shown with a single directional light. This is subtle difference since the negative value isn't the high and the decay is set to linear.