Thomas Parr

The formalist of the Friston group’s active-inference programme — the person who worked out, in bookkeeping detail, how the discrete-state (active-inference) generative model updates its beliefs and how that update maps onto neuronal message passing. Where Friston states the principle and Seth carries it into the body, Parr supplies the machine.

Why he enters an interoception wiki

He does not work on interoception. He enters through Parr et al. (2019), a visual paper, because it isolates two claims the interoceptive account depends on but rarely gets to see undisplaced:

• Attention is covert action, and covert action is precision-setting. Parr’s formalism makes “attention” a policy selected to minimise expected free energy — the same object as the precision-weighting the wiki invokes on predictive-coding and interoceptive-precision. It is the formal identity behind Farb’s finding that attention decides which cortex represents an interoceptive signal.
• Individual differences live in precision. Fixed input plus different precisions yields different perceptual phenotypes — the exteroceptive statement of the aberrant-precision story the wiki runs for interoceptive psychopathology.

His textbook with Pezzulo and Friston (Active Inference, 2022) is the standard reference for the formalism the wiki meets secondhand through Seth & Friston and Petzschner et al. Thin page: one paper in raw/.