  Adaptation to changing environments is a universal feature of life and can
involve the organism modifying itself in response to the environment as well as
actively modifying the environment to control selection pressures. The latter
case couples the organism to environment. Then, how quickly should the organism
change in response to the environment? We formulate this question in terms of
how memory duration scales with environmental rate of change when there are
trade-offs in remembering vs. forgetting. We derive a universal scaling law for
optimal memory duration, taking into account memory precision as well as two
components of environmental volatility, bias and stability. We find sublinear
scaling with any amount of environmental volatility. We use a memory complexity
measure to explore the strategic conditions (game dynamics) favoring actively
reducing environmental volatility -- outsourcing memory through niche
construction -- over investing in neural tissue. We predict stabilizing niche
construction will evolve when neural tissue is costly, the environment is
variable, and it is beneficial to be able to encode a rich repertoire of
environmental states.
