Interference in visual crowding stimuli with small separations between target and flanking stimuli

Abstract

Visual crowding occurs when flanking stimuli reduce the visibility of a target stimulus. This effect istypically stronger the closer the flanking stimuli are to the target. However, it has been observed that thistrend may be reversed causing an upturn at the very smallest separations. It has been shown previously thatcrowding may be consistent with interference in the stimuli. Interference takes place in the stimuli and doesnot depend on vision or the visual system. The present analyses examine interference between stimuli at verysmall separations. It is found that when the analyses are confined to very low spatial frequency componentsinterference may result in reduced interference at the very smallest separations. This is consistent with theupturn observed in some psychophysical experiments.

On interference between target and noise in visual stimuli

“…In this regard the adding of noise is similar to what has been found for visual crowding and masking in which the adding of masking or flanking stimuli reduces the stimulus power of a target stimulus (Skottun, 2018b, d;2020). This emphasises the need to take interference into account whenever one is interpreting the effects of adding stimulus elements.…”

“…In other words, the amplitude of the sum is smaller than the sum of amplitudes when the phases differ [FOOTNOTE 2]. As a consequence, two stimuli which differ in phase spectra cannot both have their full amplitudes contained in the amplitudes of the combined stimulus (Skottun, 2018a, b, c, d;2020). In the case of visual stimuli which involve the combining of two or more stimulus elements (such as, e.g., in visual masking, Skottun, 2018b, d, andin visual crowding, Skottun, 2020) the different elements practically always differ in their phase spectra.…”

What is a visual stimulus?

“…This is referred to as interference. (For further discussions and background material see Skottun, 2018a, b, c;2020). There may also take place interference between stimuli which are separated in time (such as, e.g., between two alternating stimuli).…”

“…For instance, a target stimulus presented on top of visual noise cannot be counted on to be the same stimulus as when presented alone (Skottun, 2021). Also, in visual crowding and masking a target stimulus cannot be assumed to be the same stimulus when presented along with flanking and masking stimuli as when it is presented by itself (Skottun, 2018b(Skottun, , 2020.…”

A few remarks on "uncrowding" in visual stimuli

“…Crowding has typically been interpreted in terms of factors in the visual system (e.g., Freeman & Simoncelli, 2011;Herzog et al, 2015;Jastrzebowska et al, 2021;Levi, 2008;Motter, 2018;Whitney & Levi, 2011). However, it has become clear that interference in the stimuli may have an effect similar to that of crowding (Skottun, 2021a, b, c;2020). This raises the question of whether or not the counteracting effect of additional stimuli, as observed in uncrowding, could be consistent with interference.…”