Decisions reduce sensitivity to subsequent information

Zohar Z. Bronfman, Noam Brezis, Rani Moran, Konstantinos Tsetsos, Tobias Donner, Marius Usher

Research output: Contribution to journalArticlepeer-review


Behavioural studies over half a century indicate that making categorical choices alters beliefs about the state of the world. People seem biased to confirm previous choices, and to suppress contradicting information. These choice-dependent biases imply a fundamental bound of human rationality. However, it remains unclear whether these effects extend to lower level decisions, and only little is known about the computational mechanisms underlying them. Building on the framework of sequential-sampling models of decision-making, we developed novel psychophysical protocols that enable us to dissect quantitatively how choices affect the way decision-makers accumulate additional noisy evidence. We find robust choice-induced biases in the accumulation of abstract numerical (experiment 1) and low-level perceptual (experiment 2) evidence. These biases deteriorate estimations of the mean value of the numerical sequence (experiment 1) and reduce the likelihood to revise decisions (experiment 2). Computational modelling reveals that choices trigger a reduction of sensitivity to subsequent evidence via multiplicative gain modulation, rather than shifting the decision variable towards the chosen alternative in an additive fashion. Our results thus show that categorical choices alter the evidence accumulation mechanism itself, rather than just its outcome, rendering the decision-maker less sensitive tonew information.

Original languageEnglish
Article number20150228
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1810
StatePublished - 24 Jun 2015


  • Changes of mind
  • Confirmation bias
  • Numerical averaging
  • Perceptual decision-making


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