Model ‘best’ was the model utilized in this work, and detailed in Figure 3. Two more complex models (+ vol,+ prevVol), as well as two simpler models (-RewRate,-RewHist) were compared through model comparison on held-out data log-likelihood.+ prevVol substituted previous wins with rewarded volume on the previous trial, and+ vol additionally substituted trial wins with rewarded volume. -RewRate omitted the sessionProgress, prevRewardRate, and previousOptOut kernels, and -RewHist further omitted the remaining reward history kernels. (A-D) Individual model comparisons. (Left) Histograms of the population-level changes in held-out negative log-likelihood demonstrate when a model performs significantly better if the median is different than 0. Significance is assessed through Wilcoxon signed rank test. in all comparisons. Median values were , , , . Sample neuron fits demonstrating the most extreme change in are shown in the middle columns, and neurons demonstrating the median change in are shown in right columns. (E) Performance of models assessed through the mean-squared error on PSTHs from held-out test data as compared to model predictions.