Across many decision-making tasks, people and animals systematically repeat (or alternate) their choices – even when the choices they make are intrinsically uncorrelated. This phenomenon (also known as ‘sequential effect’ or ‘choice hysteresis’) has been known for at least a century, and may be a stable individual trait. How do these behavioral biases arise from the activity of the brain?
We had previously shown (see publication in eLife) that individual differences in repetition behavior are driven by a specific computational process: an adjustment in the rate with which new evidence is accumulated to form a decision. In a new study with Tobias Donner, I combined behavioral modeling of a visual perceptual decision with magnetoencephalographic (MEG) analyses of neural dynamics, across multiple regions of the human cerebral cortex. This allowed us to track sensory evidence encoding and action planning, as people performed a simple decision-making task.
Role of brain activity in choice repetition bias
We found distinct signals in the parietal and motor cortex that reflected people’s previous choices and actions, respectively. Gamma-band activity in the parietal cortex tracked previous choices in a sustained fashion. On the other hand, sustained beta-band activity in the motor cortex inversely reflected the previous motor action. Behavioral modeling showed that different cortical signals mapped onto distinct computational parameters of the evidence accumulation process: parietal gamma-band power predicts a drift bias, and motor beta lateralization predicts the starting point of the DDM (Drift Diffusion Model). These signals have quite a different behavioral effect: only parietal gamma-band signals significantly mediated history bias in overt choice sequences, and differed depending on individual’s decision strategy (to repeat or alternate choices). In sum, parietal cortical signals seem to play a key role in shaping choice sequences.
Publication: Urai, A. E. & Donner, T. H. Persistent activity in human parietal cortex mediates perceptual choice repetition bias. Nat Commun 13, 6015 (2022). https://www.nature.com/articles/s41467-022-33237-5