Fig. 1.

The role of f _est in generating hereditary and behavioural variability. a In modulated stochastic causation, a time-varying non-negative deterministic variable (upper trace) is caused by other variables (arrow 1) and drives (arrow 2) the variance of a stochastic (random) process (lower trace), which then drives other variables (arrow 3). b Extended mechanism of Darwinian evolution. In the reproductive R loop an organism (probabilistically) reproduces in proportion to its fitness, f _true, which depends on a time-varying environment and on the properties of organism and population. Hereditary and behavioural variability are varied as driven by an internal estimator of fitness, f _est, implicitly made in the organism itself. Variability is high when f _est is low, and low when f _est is high (symbolized by ~1/f _est). The active A loop then continually utilizes modulated stochastic causation (arrows 1–3 as in a), and produces a genuine goal-directedness and an elementary form of agency