Just wanted to add... there is quite a lot of technology (that isn't always sorcery) that enhances or focuses psyker abilities, or protects people from psykers, and several races have that sort of thing, for the purposes of interacting with their psykers. If The Culture looks at some of that tech, even without psykers to power them, they might be able to figure out some details about the warp and psyker abilities through this.