Perceptual control theory and the free energy principle: a comparison

How do organisms pursue goals? This article compares two very different frameworks that address this question, perceptual control theory (PCT) and the free energy principle (FEP). According to PCT, organisms have goals (reference values for certain variables) and sensors (of their actual values) and act to bring the sensed values towards the references. That is, they are organised as assemblages of control systems. FEP views the behaviour of organisms as resulting from minimising a quantity called free energy. PCT makes specific proposals for the organisation of multiple control systems and for other aspects of goal-seeking behaviour, such as adaptation, learning, and memory. FEP claims that these phenomena and others emerge from the single principle of free energy minimisation. PCT sharply distinguishes action from prediction: they are different sorts of things. FEP treats action as a particular case of prediction: organisms act not by commanding but by predicting their future states. • Perceptual control theory asserts that an organism's actions are undertaken to control its perceptions. • The free energy principle unifies action with prediction as aspects of minimising free energy. • The two theories differ fundamentally. It remains to be seen how this disaccord may be resolved.