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Detecting spatial targets in complex backgrounds is a fundamental visual task. Detectability decreases with increasing retinal eccentricity. Detectability is also affected by the properties of the background surrounding and under the target, an effect known as masking. Previous research has used additive targets, where the target intensities are added to the background. Previous research shows that background contrast explains much of the variance in foveal and peripheral detectability. Furthermore, the masking of additive targets operates in a lawful manner: Target threshold power increases linearly with background contrast power. In natural viewing, however, targets occlude the background, replacing background features with target features. It is currently unknown whether the laws that apply to additive targets extend to occluding targets. We began our investigation with an experiment using two occluding targets …