On interference between target and noise in visual stimuli

Abstract

Visual stimuli in which a target is presented on a background of noise have been used widely in visionresearch. Adding a background of noise tends to reduce performance. Such reductions have typically beenattributed to factors in the visual system. The present analyses demonstrates how there may be interferencebetween target and noise. This interference takes place in the stimuli rather than in the visual system. Ittakes place even if the stimuli are not being seen. The interference causes the amplitudes in the combinedtarget and noise stimulus to be smaller than the amplitudes in the target plus the amplitudes in the noisewhen these are determined separately. Therefore, the full amplitudes of the target and those of the noisecannot all be contained in the amplitudes of the combined stimulus. As a consequence one cannot counton a target stimulus to have the same stimulus power when presented on a background of noise as whenpresented on a uniform background.