Once cognition is recognized as having a 'dual' information source, the information theory chain rule implies that isolating coresident information sources from crosstalk requires more metabolic free energy than permitting correlation. This provides conditions for an evolutionary exaptation leading to the rapid, shifting global neural broadcasts of consciousness. The argument is quite analogous to the well-studied exaptation of noise to trigger stochastic resonance amplification in neurons and neuronal subsystems. Astrobiological implications are obvious
