The role of distractors in object substitution masking.

Abstract

In object substitution masking (OSM) a surrounding mask (typically comprising of 4 dots) onsets with a target but lingers after offset; under such conditions, the ability to perceive the target can be significantly reduced. OSM was originally claimed to occur only when a target was not the focus of attention, for instance, when embedded in an array of distractors (Di Lollo, Enns, & Rensink, 2000). It was argued that the distractors influenced the time taken for focal attention to reach the target. Some recent work, however, failed to find any such distractor influence; the effect of mask duration was found to be independent of set size when steps were taken to avoid ceiling effects in the smallest set size condition (Argyropoulos, Gellatly, Pilling, & Carter, 2013; Filmer, Mattingley, & Dux, 2014). In 3 experiments, we repeatedly found that set size manipulations can interact with mask duration (in which neither ceiling nor floor effects are evident), with the effect of the mask on target perceptibility being amplified according to the number of distractor items. However, a further experiment (Experiment 4) showed that crowding by nearby distractors was actually responsible for this "set size" effect. When decoupled from crowding, set size alone did not interact with masking, though it did influence overall accuracy. Thus, the presence of distractors does influence OSM, but not in the way originally assumed by Di Lollo and colleagues in their model. The Crowding × OSM interaction suggests that the 2 phenomena involve partly overlapping mechanisms.

The role of executive attention in object substitution masking

“…Recent studies have now provided definitive evidence that OSM magnitude does not interact with spatial attention demands (Argyropoulos, Gellatly, Pilling, & Carter, 2013;Camp, Pilling, Argyropoulos, & Gellatly, 2015;Filmer, Mattingley, & Dux, 2014). Specifically, these studies have shown that past reports finding a strong link between spatial attention and OSM have been driven by ceiling effects for the smaller distractor set size conditions.…”

“…Thus, it is still possible that nonspatial forms of attention could interact with masking. Indeed, manipulations of spatial attention inherently involve potential confounds of crowding (Camp et al, 2015;Vickery, Shim, Chakravarthi, Jiang, & Luedeman, 2009), and spatial uncertainty. Such confounds may interact with masking processes (Camp et al, 2015), and hence complicate the assessment of the role of attention in OSM.…”

“…Indeed, manipulations of spatial attention inherently involve potential confounds of crowding (Camp et al, 2015;Vickery, Shim, Chakravarthi, Jiang, & Luedeman, 2009), and spatial uncertainty. Such confounds may interact with masking processes (Camp et al, 2015), and hence complicate the assessment of the role of attention in OSM. In contrast, manipulations of executive/temporal attention avoid these issues as the presentation conditions of the target and mask stimuli can be identical across attention manipulations.…”

Categorical information influences conscious perception: An interaction between object-substitution masking and repetition blindness

“…They concluded that the suppression characteristic of object substitution occurs higher up in system than visual crowding (Chakravarthi & Cavanagh, 2009). Others have however found that crowding and OSM do appear to interact in some circumstances (Camp et al, 2015). We suggest that while crowding and OSM have different loci and reflect dissociable underlying mechanisms, crowding can impact on the objectfile formation mechanisms underlying OSM.…”

“…While, as flagged earlier, the presence of simultaneous distractors is not a necessary condition for OSM, and there have been absences of interactions between masking and set-size in OSM reported when the items are widely spaced (Argyropoulos et al, 2013;Filmer et al, 2014), when the distractors are sufficiently close to the target to induce crowding, then an interaction between masking magnitude and the number of distractors is obtained (Camp, Pilling, Argyropoulos, & Gellatly, 2015). This interaction between crowding and OSM suggests that there may be at least some overlap in mechanisms; otherwise purely additive effects would be expected.…”