Using psychophysics to ask if the brain samples or maximizes

Daniel E. Acuna, Max Berniker, Hugo L. Fernandes, Konrad P. Kording

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The two-alternative forced-choice (2AFC) task is the workhorse of psychophysics and is used to measure the just-noticeable difference, generally assumed to accurately quantify sensory precision. However, this assumption is not true for all mechanisms of decision making. Here we derive the behavioral predictions for two popular mechanisms, sampling and maximum a posteriori, and examine how they affect the outcome of the 2AFC task. These predictions are used in a combined visual 2AFC and estimation experiment. Our results strongly suggest that subjects use a maximum a posteriori mechanism. Further, our derivations and experimental paradigm establish the already standard 2AFC task as a behavioral tool for measuring how humans make decisions under uncertainty.

Original languageEnglish (US)
Pages (from-to)1-16
Number of pages16
JournalJournal of Vision
Issue number3
StatePublished - 2015
Externally publishedYes


  • Bayesian
  • Decision-making
  • Just-noticeable difference (JND)
  • Maximum a posteriori
  • Psychophysics
  • Sampling
  • Two-alternative forced choice (2AFC)

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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