title: Using psychophysics to ask if the brain samples or maximizes.
abstract: 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.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Sciences, Northwestern University, Chicago, IL, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Acuna
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, USA Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA.
authors.forename: Max
authors.initials: M
authors.lastname: Berniker
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA PDBC, Instituto Gulbenkian de Ciência, Oeiras, Portugal Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Hugo L
authors.initials: HL
authors.lastname: Fernandes
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Sciences, Northwestern University, Chicago, IL, USA Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, USA.
authors.forename: Konrad P
authors.initials: KP
authors.lastname: Kording
mesh_terms: D001921:Brain / Q000502:physiology*; D002755:Choice Behavior; D003657:Decision Making; D006801:Humans; D008433:Mathematics; D008962:Models, Theoretical; D011601:Psychophysics / Q000379:methods*
keywords: Bayesian; decision-making; just-noticeable difference (JND); maximum a posteriori; psychophysics; sampling; two-alternative forced choice (2AFC)