Article Figures & Data
Figures
- Figure 1.
A, Following a self-paced button press, a checkerboard stimulus was presented whose contrast changed linearly. The participant could at any time select the contrast displayed on screen by pressing a button with the right index finger. The trial continued until a button was pressed or until stimulus duration exceeded 30 s. Following the participant’s choice, the selected contrast remained on screen for 2 s, after which time the monetary reward associated with the chosen contrast was displayed for 2.5 s. In the event that no button was pressed within 30 s, feedback was a message reminding the participant of the task instructions. B, Two demonstrative examples of stimulus contrast as a function of elapsed time. Example trial 1 (blue) has an initial contrast of 63%, is initially increasing, and has a half-cycle period of 9 s. Example trial 2 (red) has an initial contrast of 39%, is initially decreasing, and has a half-cycle period of 6 s. The checkerboard stimulus phase reversed at a rate of 12 Hz. C, Functional mapping between the contrast difference from target and monetary reward. The mapping was a symmetrical triangular function with a center of 0% contrast difference, a half-width of 15% contrast difference, and a height of 25 cents. As such, the received reward was maximal when the participant responded at the target contrast and decreased linearly with increasing difference of chosen contrast from the target. The reward was 0 for responses at >15% distance. Feedback received was rounded to the nearest whole-cent value.
- Figure 2.
Mean accuracy as a function of within-block trial number across participants. Accuracy is presented as the absolute difference of chosen and target contrasts, where lower differences indicate better task performance. Error bars represent the SEM. Note that the number of trials per block varied across blocks and participants, and as a result some participants did not complete >19 trials in any block. This confound limited the interpretability of accuracy data for trial numbers >20, and the final data point of the series therefore represents mean accuracy across trials 19–25 for each participant.
- Figure 3.
Computational belief variables as a function of trial number. A, Belief entropy. B, Feedback surprise. C, Belief update size measured as mutual information (see Eq. 14). D, Belief update size measured as Bayesian surprise (see Eq. 15). Note that the number of trials per block varied across blocks and participants, and, as a result, some participants did not complete >19 trials in any block. This confound limited the interpretability of computational belief variables for trial numbers >20, and the final data point of the each series therefore represents a mean across trials 19–25 for each participant. Error bars represent the SEM.
- Figure 4.
P3 analysis. A, Median split waveforms for 200–1000 ms following visual presentation of feedback. The P3 regression analysis window is indicated by the gray bar. ERP waveforms were low-pass filtered at 30 Hz for display purposes only. B, Mean voltage topography during the P3 analysis window from 300 to 450 ms following visual presentation of feedback (time = 0). C, Topography of the mean voltage difference between large and small belief update trials across participants during P3 analysis window. A median split was used to divide trials into two bins for each participant, corresponding to large and small belief updates according to model-derived estimates. This median split was for display purposes only and was not used in the main regression analysis, which was based on single-trial amplitudes.
- Figure 5.
Stimulus-preceding negativity analysis. A, Median split waveforms for 0–1500 ms prior to the visual presentation of feedback. The SPN regression analysis window from 0 to 500 ms preceding feedback is indicated by the gray bar. ERP waveforms were low-pass filtered at 30 Hz for display purposes only. B, Mean voltage topography during SPN analysis window from 0 to 500 ms prior to visual presentation of feedback (time = 0). C, Topography of the mean voltage difference between high and low uncertainty trials across participants during the SPN analysis window. A median split was used to divide trials into two bins for each participant, corresponding to high and low belief uncertainty according to model-derived estimates. This median split was for display purposes only and was not used in the main regression analysis, which was based on single-trial amplitudes.
Tables
Data structure Type of test Observed power a Normally distributed Single-sample t test 1.0 b Model likelihoods BIC Not applicable c Normally distributed Single-sample t test 1.0 d Normally distributed Single-sample t test 0.54 e Normally distributed Single-sample t test 0.65 f Normally distributed Single-sample t test 0.06 g Normally distributed Single-sample t test 1.0 h Normally distributed Pearson correlation 0.99 i Normally distributed Single-sample t test 0.95 j Normally distributed Single-sample t test 1.0 k Normally distributed Repeated-measures ANOVA 0.77 l Normally distributed Repeated-measures ANOVA 0.08 m Normally distributed Repeated-measures ANOVA 0.13 n Normally distributed Single-sample t test 0.31 o Normally distributed Single-sample t test 0.97 p Normally distributed Single-sample t test 0.98 q Normally distributed Single-sample t test 1.0 Model Parameters per participant Parameters Belief distribution Log-likelihood BIC N best fit Unbiased updating 1 σ Yes −20190 40515 11 Win-stay/lose-shift 1 σ No −20350 40834 5 Reward Belief update size (I) Belief update size (IKL ) Reward 1 Belief update size (I) 0.22 (0.19) 1 Belief update size (IKL ) −0.24 (0.12) 0.64 (0.16) 1 Surprise 0.45 (0.21) 0.22 (0.12) 0.05 (.14) Data are presented as mean Spearman coefficient across participants (SD).
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