Two-Step Task with Transition Probability Reversals(A) Diagram of apparatus and trial events.(B) State diagram of task. Reward and transition probabilities are indicated for one of the six possible block types.(C) Block structure; left side shows the three possible states of the reward probabilities, right side shows the two possible states of the transition probabilities.(D) Example session. Top panel: exponential moving average (tau = 8 trials) of choices. Horizontal gray bars show blocks, with correct choice (top, bottom, or neutral) indicated by y position of bars. Middle panel: reward probabilities in left-active (red) and right-active (blue) states. Bottom panel: transition probabilities linking first-step actions (top, bottom pokes) to second-step states (left/right active).(E) Choice probability trajectories around reversals. Pale blue line, average trajectory; dark blue line, exponential fit; shaded area, cross-subject SD. Left panel: reversals in reward probability; right panel: reversals in transition probabilities.(F) Second step reaction times following common and rare transitions (i.e., the time between the first-step choice and side poke entry). ∗∗∗p < 0.001 Error bars show cross-subject SEM.
