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An optimal agent will base judgments on the strength and reliability of decision-relevant evidence. However, previous investigations of the computational mechanisms of perceptual judgments have focused on integration of the evidence mean (i.e., strength), and overlooked the contribution of evidence variance (i.e., reliability). Here, using a multielement averaging task, we show that human observers process heterogeneous decision-relevant evidence more slowly and less accurately, even when signal strength, signal-to-noise ratio, category uncertainty, and low-level perceptual variability are controlled for. Moreover, observers tend to exclude or downweight extreme samples of perceptual evidence, as a statistician might exclude an outlying data point. These phenomena are captured by a probabilistic optimal model in which observers integrate the log odds of each choice option. Robust averaging may have evolved to mitigate the influence of untrustworthy evidence in perceptual judgments.

Original publication

DOI

10.1073/pnas.1104517108

Type

Journal article

Journal

Proc Natl Acad Sci U S A

Publication Date

09/08/2011

Volume

108

Pages

13341 - 13346

Keywords

Adult, Color Perception, Computer Simulation, Decision Making, Humans, Judgment, Models, Biological, Perception, Regression Analysis, Task Performance and Analysis, Young Adult