From a laboratory in Tokyo, researchers have given mathematical form to one of life's oldest negotiations: the cost of remembering. A team spanning the University of Tokyo and RIKEN has shown that organisms across every scale of life — from bacteria to brains — do not simply accumulate memory, but toggle it on and off depending on what they can afford and what the world is telling them. In the calculus of survival, forgetting is not failure; sometimes it is the most intelligent move available.