Irradiation, border location, and the shifted-chessboard pattern

Area of Science:

• Visual Perception
• Neuroscience
• Optics

Background:

• The perceived location of a black-white border deviates towards the black side.
• Previous studies have investigated this border shift phenomenon.

Purpose of the Study:

• To precisely measure the magnitude of the border position shift in foveal vision.
• To elucidate the underlying optical and neural mechanisms contributing to this visual perception.
• To explain the shifted-chessboard illusion using a multi-stage model.

Main Methods:

• Quantitative measurement of the border shift effect in normal observers.
• Modeling the visual system using the Naka-Rushton equation for light intensity nonlinearity.
• Incorporating Difference of Gaussians (DoG) center-surround transformation.
• Analyzing retinal and cortical contributions to visual illusions.

Main Results:

• A border shift of approximately 0.4 min of arc was measured at medium photopic luminances.
• Retinal light spread and compressive nonlinearity (Naka-Rushton) partially explain the border shift.
• A model including center-surround (DoG) processing accounts for shape deviations in the shifted-chessboard illusion.
• Cortical mechanisms contribute to sharp border perception, monotonic slopes, and Zöllner-like orientation deviations.

Conclusions:

• The perceived border shift is a complex visual phenomenon influenced by both retinal and cortical processes.
• Light spread, compressive nonlinearity, and center-surround interactions are key retinal factors.
• Cortical processing generates features like sharp borders, specific line slopes, and orientation illusions.