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Happy to share the result of a fruitful collaboration with @carinafo.bsky.social out in Computational Brain & Behavior: Two Paths to Bias: Distinct Influences of Stimulus Probability and Previous Choice on Drift Diffusion Parameters (link.springer.com/article/10.1...)

TL;DR: What we expect and what we just did bias decisions in different ways. While both effects are generally stable concerning the volatility of environments, how they play out in the brain depends on the stability of stimulus probabilities in the environment.

We investigated two sources of bias in near-threshold perceptual decisions: stimulus probabilities (communicated with explicit probability cues) and previous choices in two different environments: stable vs. volatile, depending on whether stimulus probabilities change on a trial-level.

We used a joint model, integrating pre-stimulus Beta power over sensory areas into a hierarchical drift-diffusion model to see how the biases play out in the decision process and what role activation prior to stimulus onset plays in implementing these biases.

Probability cues consistently shift the starting point of evidence accumulation, whereas previous choices bias the drift rate: two distinct computational routes to biased decisions. But!...