Is the straddle effect in contrast perception limited to second-order spatial vision?

Area of Science:

• Visual perception
• Human contrast processing

Background:

• Previous research on the straddle effect used spatially second-order visual patterns.
• The straddle effect is a performance drop when test contrasts straddle the adaptation contrast.

Purpose of the Study:

• To determine if spatially first-order patterns are sufficient to elicit the straddle effect.
• To investigate contrast normalization with first-order patterns.
• To compare performance between first- and second-order tasks.

Main Methods:

• Demonstrated the straddle effect using spatially first-order visual patterns.
• Employed several different observer tasks.
• Observed contrast normalization effects analogous to second-order patterns.

Main Results:

• The straddle effect was successfully demonstrated using first-order visual patterns.
• Contrast normalization effects were observed with first-order patterns.
• Performance in first-order tasks was slightly lower than in second-order tasks, possibly due to memory load.

Conclusions:

• Spatially second-order patterns are not necessary for the straddle effect.
• Human contrast processing may involve a comparison to recent average contrast, not just monotonic physical contrast.
• The straddle effect is a robust phenomenon observable across different visual pattern types.