Fig. 1.

Psychophysical characterization and modeling of perception. (A) Perception of a stimulus variable (e.g., the angular tilt ${\theta }_0$ of the leaning tower of Pisa) can be characterized by an observer’s discrimination threshold and perceptual bias. Discrimination threshold specifies how well an observer can discriminate small deviations around the particular stimulus orientation ${\theta }_0$ given that there is noise in perceptual processing (green arrow). Perceptual bias specifies how much, on average, the perceived orientations over repeated presentations (thin lines) deviate from the true stimulus orientation (blue arrow). (B) Modeling perception as an encoding–decoding processing cascade. Discriminability is limited by the characteristics of the encoding process, i.e., the quality of the internal, sensory representation $\stackrel{\sim }{m}$. Perceptual bias, however, also depends on the decoding process that typically involves cognitive factors such as prior beliefs and reward expectations. Both discrimination threshold and perceptual bias can be characterized with appropriate psychophysical methods (indicated by dashed arrows).