Fig 4. True and estimated stimulus transition contingencies for two example participants.

(A) Transitions between pairs of stimuli, from trial t-1 to trial t, were defined by TMs. Every 50 trials, the TM switched to a different matrix. (B) Each panel corresponds to 1 of 16 possible transitions between stimuli across 1,200 trials. The black lines indicate the true transition contingencies. The blue lines reflect the participant’s inferred estimates (i.e., the posterior expectation of these contingencies, ${\widehat{\mu }}_1$), before seeing the stimulus outcome on each trial. The model tracked the true underlying contingencies and detected change points. In a representative participant from the Placebo group, the model tracked the true transition contingencies closely. An example participant from the ACh- group showed a greater discrepancy in the tracking of the true transition contingencies. This is reflected in the two participants’ ω estimates: Placebo Participant 2 showed a higher transition contingency learning rate (ω = −3.27) than ACh- Participant 16 (ω = −5.84). http://dx.doi.org/10.6084/m9.figshare.3796362.v2.