Site of the accelerating nonlinearity underlying luminance-change detection

Area of Science:

• Visual neuroscience
• Perception science

Background:

• Visual psychometric functions for luminance-increment detectability (d') show acceleration with stimulus energy.
• Existing models explain this acceleration and how luminance pedestals linearize the function.

Purpose of the Study:

• To investigate the origin of nonlinearity in the visual psychometric function.
• To test whether central or peripheral processing accounts for the observed nonlinearities.

Main Methods:

• An experiment was conducted using dichoptically presented luminance increments.
• The effect of a dichoptic pedestal on signal detection and psychometric function linearity was measured.

Main Results:

• A dichoptically presented increment was found to linearize the psychometric function.
• This dichoptic condition facilitated the detection of weak signals.
• Central combination of the dichoptic pedestal with the signal was inferred.

Conclusions:

• The results indicate that the nonlinearity in the visual psychometric function originates from central processing stages.
• This finding supports the uncertainty model of visual perception.
• A model requiring a nonlinear transducer is less compatible with the experimental data.