I have liked Friston’s ideas for some time, so what a shock it is to find him defending Freudian ideas. Naïve me, I thought that Freud’s model was dead in the water. Why? It is untested, does not fit with current evidence and, further, is probably untestable therefore not good science. It fails the Occam’s razor test and so is not even good philosophy. It relies heavily on introspection which is unreliable as a source of information about anything except introspection itself. Friston does not seem to put forward any good reason for trying to raise the dead.

In terms of theoretical and computational neuroscience, we will focus of Helmholtz’s suggestion that the brain is an inference machine; this idea is now a fundamental premise in neurobiology. Key examples of this include the Bayesian brain, predictive-coding and the free-energy principle. This framework assumes that the brain uses internal hierarchical models to predict its sensory input and suggests that neuronal activity (and synaptic connections) try to minimize the ensuing prediction-error or (Helmholtz) free-energy. This free-energy is a measure of surprise and is essentially the amount of prediction-error. It is an information theory quantity that, mathematically, plays the same role as free-energy in statistical thermodynamics. Free-energy is not an abstract concept; it can be quantified easily and is used routinely in modelling empirical data and in neuronal simulations of perception and action.

We have an analogy, a metaphor, here. Parts of this framework are accepted by various neuroscientists but not necessarily literally. In the context of the brain, free-energy is abstract and is metaphoric.

When the term energy is used by Freud, it is also a metaphor. Freud’s mind is divided into id, ego and superego. The id, home of primitive drives and pleasure seeking, is bubbling with free libido energy. The ego tries to control the id to conform to reality, social rules, perception, judgement by reducing that energy from the id.

This Freudian use of the word ‘energy’ has nothing to do the thermodynamics use and neither has anything to do with use in predictive error reduction. Freud and thermodynamics share a word; thermodynamics and Friston’s version of error reduction share equations, a mathematical structure. The flow of electricity and of water share equations, that does not make them physically similar. Optics and weight share the word ‘light’ but that does not make them similar.

Friston carries on and does some damage to the idea of hierarchy in brain processes and the default network in order to make them fit with the primary and secondary Freudian processes.

Would it not be better to allow Freud’s terrible theory to just fade away? Do we really need to have people struggle with the myth that they have a sex craved monster living in the cellar of their minds?

Carhart-Harris, R., & Friston, K. (2010). The default-mode, ego-functions and free-energy: a neurobiological account of Freudian ideas Brain, 133 (4), 1265-1283 DOI: 10.1093/brain/awq010