Before revision:  The performance of belief updating is scored in terms of information length , a measure of the distance traveled in information space , which has a direct interpretation in terms of metabolic efficiency. These results show that active inference is consistent with state-of-the-art models of neuronal dynamics and coincides with the natural gradient. This suggests that natural selection, by selecting the phenotypes that optimise metabolic and computational efficiency, has implicitly approximated the steepest direction in information space ;
After revision:  The performance of belief updating is scored in terms of information length , a measure of the distance traveled in information space , which has a direct interpretation in terms of metabolic cost. We show that neural dynamics under active inference are metabolically efficient and suggest that neural representations in biological agents may evolve by approximating steepest descent in information space ;