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I'm trying to remember a novel I read in the late 1980s or early 1990s. Earth has been taken over by a robotic culture that has destroyed almost everything animal, vegetable, or human. A small number of humans survive like vermin in the corners, sneaking food, tools, and other supplies out of the factories. The different parts of the robotic culture are not completely unified into a single planetary mind. One faction has been experimenting with humans and has joined together some number (5? 8?) of humans at the temples. This "human starfish" can think as a single entity to some degree, and floats in a sort of amniotic tank in the robot's laboratory.