Casper Kerrén
ckerren.bsky.social
Casper Kerrén
@ckerren.bsky.social
Postdoc Max Planck Institute for Human Cognitive and Brain Sciences.
We don’t learn the world as it is. We rapidly infer what matters, with belief and attention reciprocally shaping each other as neural geometry adapts.

Thanks to @stephanie-theves.bsky.social, @mikael-johansson.bsky.social, Peter Gärdenfors, @doellerlab.bsky.social.

www.biorxiv.org/content/10.1...
Inference over hidden contexts shapes the geometry of conceptual knowledge for flexible behaviour
Flexible decision-making in uncertain environments requires inferring the relevant context and focusing on behaviourally relevant information. We tested the hypothesis that the brain supports this pro...
www.biorxiv.org
January 8, 2026 at 7:46 AM
Critically, inference stretches neural distances along relevant dimensions and compresses irrelevant ones right before a decision, predicts faster RTs, and this re-shaping precedes feedback-related frontal theta tracking model-derived PE.
January 8, 2026 at 7:46 AM
The brain’s representational space flexes with inferred complexity.

Neural effective dimensionality scales up in 2D vs 1D, and is higher on correct vs incorrect trials. In 2D, the two attended features show up as near-orthogonal axes in a shared planar manifold plane.
6/8
January 8, 2026 at 7:46 AM
Eyes tell the same story
Gaze selectively shifts toward task-relevant features, irrelevant features drop out. Gaze entropy decreases as beliefs stabilise, and negative prediction errors from the HSI model trigger broader sampling (exploration), while positive PEs tighten focus (exploitation).
5/8
January 8, 2026 at 7:46 AM
A Hidden State Inference (HSI) model best explained choices and inferred contexts, beating Q-learning variants (standard, forgetting, counterfactual).

HSI captures something structurally different from incremental RL.
4/8
January 8, 2026 at 7:46 AM
Participants adapted fast: first trial after a switch was at chance level, then rapid recovery. RTs drop and accuracy rises within context blocks - they used the structure to take decisions.
3/8
January 8, 2026 at 7:46 AM
Serial reversal learning task with same cars, same feature space (3 dimensions), but the rule silently flips. Different dimensions matter in different trials. Sometimes one dim matters, sometimes two dims. You only find out via feedback, meaning participants had to infer the latent state.
2/8
January 8, 2026 at 7:46 AM
Having worked at the Max Planck Institute for Human Development in Berlin, it is hard not to find this advice laughable coming from a group that seems to foster anything but open culture and flat hierarchies.
January 8, 2026 at 6:47 AM