Substitution Masking Research Articles

The influence of a salient distractor in object-substitution masking

It remains unclear whether a salient distractor directly affects performance accuracy and the perceptual resolution of a target. In order to investigate this issue, the present study employed object substitution masking (OSM) to index perceptual hypothesis testing of a target. Trailing-mask duration of the four-dot mask was varied to investigate how the representation of the masked target decayed over time. Participants responded to the presence of a vertical line on a target ring that was isolated by a four-dot mask while an irrelevant salient distractor was presented in a subset of trials. The results revealed that the salient distractor only impacted performance when the mask and target offset concurrently (Experiment 1) or at short mask durations (Experiment 2). At longer mask durations performance in the distractor present condition was identical to performance in the distractor absent condition, suggesting that involuntary capture of attention did not affect OSM. These results show that the perceptual resolution of a masked target can operate independently of involuntary attentional selection.

Substituting objects from consciousness: A review of object substitution masking

Object substitution masking (OSM) occurs when a sparse (e.g., four-dot), temporally trailing mask obscures the visibility of a briefly presented target. Here, we review theories of OSM: those that propose that OSM reflects the interplay between feedforward and feedback/reentrant neural processes, those that predict that feedforward processing alone gives rise to the phenomenon, and theories that focus on cognitive explanations, such as object updating. We discuss how each of these theories accommodates key findings from the OSM literature. In addition, we examine the relationship between OSM and other visual-cognitive phenomena, including object correspondence through occlusion, change blindness, metacontrast masking, backward masking, and visual short-term memory. Finally, we examine the level of processing at which OSM impairs target perception. Collectively, OSM appears to reflect the conditions under which the brain confuses two visual events for one when they are encoded with low spatiotemporal resolution, due to processing resources being otherwise occupied.

Is the whole really more than the sum of its parts? Estimates of average size and orientation are susceptible to object substitution masking.

We have a remarkable ability to accurately estimate average featural information across groups of objects, such as their average size or orientation. It has been suggested that, unlike individual object processing, this process of feature averaging occurs automatically and relatively early in the course of perceptual processing, without the need for objects to be processed to the same extent as is required for individual object identification. Here, we probed the processing stages involved in feature averaging by examining whether feature averaging is resistant to object substitution masking (OSM). Participants estimated the average size (Experiment 1) or average orientation (Experiment 2) of groups of briefly presented objects. Masking a subset of the objects using OSM reduced the extent to which these objects contributed to estimates of both average size and average orientation. Contrary to previous findings, these results suggest that feature averaging benefits from late stages of processing, subsequent to the initial registration of featural information.

Reduced OSM for long duration targets: Individuation or items loaded into VSTM?

Typical studies of object substitution masking (OSM) employ a briefly presented search array. The target item is indicated by a cue/mask that surrounds but does not overlap the target and, compared to a common offset control condition, report of the target is reduced when the mask remains present after target offset. Given how little observers are able to report of item arrays that have been presented for several hundred milliseconds (Wolfe, Reinecke, & Brawn, 2006), it might be expected that OSM would also be found if the search array is presented for an extended period before the target is cued by onset of a mask surrounding it. However, Gellatly, Pilling, Carter, and Guest (2010) reported that under these conditions OSM is greatly reduced. This target duration effect could be due to identity information about the search array having been loaded into VSTM during the precue period. Alternatively, it can be understood in terms of target/mask individuation and the object updating account of OSM (Lleras & Moore, 2003). The present article reports three experiments investigating which of these possibilities provides the better explanation of the effect of target duration on OSM. The results support the individuation hypothesis and, thereby, the object updating account of OSM.

Mask-target color congruency enhances object substitution masking in the presence of an attentional control set

Mask-target color congruency enhances object substitution masking in the presence of an attentional control set

Mask-target color congruency enhances object substitution masking in the presence of an attentional control set

Mask-target color congruency enhances object substitution masking in the presence of an attentional control set

Revealing the face behind the mask: Emergent unconscious perception in object substitution masking

Revealing the face behind the mask: Emergent unconscious perception in object substitution masking

Is reentry critical for visual awareness of object presence?

Reentrant processing has been proposed as a critical mechanism in visual perception of an object’s features. In order to test whether reentry is critical for visual awareness of object presence, the success of reentry was manipulated with object substitution masking (OSM) while participants performed a forced-choice target present–absent task and rated their subjective confidence in each trial. Signal detection analyses were performed on the data from the forced-choice task and on the subjective confidence ratings. The results showed that OSM reduced sensitivity to the presence of the target, indicating that reentry is critical for awareness of object presence. Consistent with the idea that OSM leaves feedforward processing intact, confidence ratings in reported target-absent trials were lower for misses (target present, no response) than for correct rejections (target absent, no response), implying that a target-related sensory signal was available for subjective ratings in spite of reported absence of the target. The results suggest that reentry is critical for encoding the target representation into a stable, consciously reportable form.

Understanding recovery from object substitution masking

When we look at a scene, we are conscious of only a small fraction of the available visual information at any given point in time. This raises profound questions regarding how information is selected, when awareness occurs, and the nature of the mechanisms underlying these processes. One tool that may be used to probe these issues is object-substitution masking (OSM). In OSM, a sparse, temporally-trailing four dot mask can interfere with target perception, even though the target and mask have different contours and do not spatially overlap ( Enns & Di Lollo, 1997). Here, we investigate the mechanisms underlying the recently discovered recovery from OSM observed with prolonged mask exposure ( Goodhew, Visser, Lipp, & Dux, 2011). In three experiments, we demonstrate that recovery is unaffected by mask offset, and that prolonged physical exposure of the mask is not necessary for recovery. These findings confirm that recovery is not due to: (a) an offset transient impairing the visibility of other stimuli that are nearby in space and time, or (b) mask adaptation or temporal object-individuation cues resulting from prolonged mask exposure. Instead, our results confirm recovery as a high-level visual-cognitive phenomenon, which is inherently tied to target-processing time. This reveals the prolonged iterative temporal dynamics of conscious object perception.

Reentrant Visual Processing Affects Rapid Object Categorization in Natural Scenes

The human visual system is very fast and efficient at extracting information about objects present in complex natural scenes. For example, Thorpe, Fize, and Marlot (1996) showed that participants were able to decide whether a natural scene contained an animal even when the image was presented briefly. Moreover, Rousselet, Fabre-Thorpe, and Thorpe (2002) used the animal versus non-animal categorization task and showed that participants could reliably indicate the side containing an animal when two images were simultaneously flashed in the left and right hemi-fields. Together, these results suggest that a great deal of visual information is processed in a fast and feedforward way so that object categorization in natural scenes can be achieved rapidly. The current study aimed to examine whether recurrent visual processing plays a role in rapid object categorization in natural scenes by using an object substitution masking paradigm. We had participants perform an object categorization task. On each trial, two images were simultaneously presented for 20 ms in the left and right visual fields; participants then had to indicate whether an animal or a vehicle appeared in the target picture, which was surrounded by eight dots. These dots either disappeared simultaneously with the target and distractor pictures or remained on the screen for 200 ms. According to Di Lollo, Enns, and Rensink (2000), object substitution masking occurs when a lateral mask (e.g., small dots) persists beyond the duration of a target, reflecting reentrant processes in vision. Therefore, the trailing dots should not affect categorization performance if rapid object categorization requires no reentrant processing from higher-level visual areas. However, our results showed that the trailing dots impaired participants' categorization performance, suggesting that reentrant visual processing affects rapid object categorization in natural scenes.

Collinearity and Containment Grouping have Different Effects on Object Substitution Masking

Collinearity and Containment Grouping have Different Effects on Object Substitution Masking

Implicit semantic perception in object substitution masking

Decades of research on visual perception has uncovered many phenomena, such as binocular rivalry, backward masking, and the attentional blink, that reflect 'failures of consciousness'. Although stimuli do not reach awareness in these paradigms, there is evidence that they nevertheless undergo semantic processing. Object substitution masking (OSM), however, appears to be the exception to this rule. In OSM, a temporally-trailing four-dot mask interferes with target perception, even though it has different contours from and does not spatially overlap with the target. Previous research suggests that OSM has an early locus, blocking the extraction of semantic information. Here, we refute this claim, showing implicit semantic perception in OSM using a target-mask priming paradigm. We conclude that semantic information suppressed via OSM can nevertheless guide behavior.

The effect of spatial competition between object-level representations of target and mask on object substitution masking

One of the processes determining object substitution masking (OSM) is thought to be the spatial competition between independent object file representations of the target and mask (e.g., Kahan & Lichtman, 2006). In a series of experiments, we further examined how OSM is influenced by this spatial competition by manipulating the overlap between the surfaces created by the modal completion of the target (an outline square with a gap in one of its sides) and the mask (a four-dot mask). The results of these experiments demonstrate that increasing the spatial overlap between the surfaces of the target and mask increases OSM. Importantly, this effect is not caused by the mask interfering with the processing of the target features it overlaps. Overall, the data indicate, consistent with Kahan and Lichtman, that OSM can arise through competition between independent target and mask representations.

Competing for consciousness: Prolonged mask exposure reduces object substitution masking.

In object substitution masking (OSM) a sparse, temporally trailing 4-dot mask impairs target identification, even though it has different contours from, and does not spatially overlap with the target. Here, we demonstrate a previously unknown characteristic of OSM: Observers show reduced masking at prolonged (e.g., 640 ms) relative to intermediate mask durations (e.g., 240 ms). We propose that with prolonged exposure, the mask's visual representation is consolidated, which allows processing of the lingering target icon to be reinitiated, thereby improving performance. Our findings suggest that when the visual system is confronted with 2 temporally contiguous stimuli, although one may initially gain access to consciousness above the other, the "losing" stimulus is not irreversibly lost to awareness.

Relationship between visual binding, reentry and awareness

Visual feature binding has been suggested to depend on reentrant processing. We addressed the relationship between binding, reentry, and visual awareness by asking the participants to discriminate the color and orientation of a colored bar (presented either alone or simultaneously with a white distractor bar) and to report their phenomenal awareness of the target features. The success of reentry was manipulated with object substitution masking and backward masking. The results showed that late reentrant processes are necessary for successful binding but not for phenomenal awareness of the bound features. Binding errors were accompanied by phenomenal awareness of the misbound feature conjunctions, demonstrating that they were experienced as real properties of the stimuli (i.e., illusory conjunctions). Our results suggest that early preattentive binding and local recurrent processing enable features to reach phenomenal awareness, while later attention-related reentrant iterations modulate the way in which the features are bound and experienced in awareness.

Study of Object Substitution Masking Using Event-related Potential

Study of Object Substitution Masking Using Event-related Potential

Implicit semantic perception in object substitution masking

Decades of research on visual perception has uncovered many phenomena, such as binocular rivalry, backward masking, and the attentional blink, that reflect ‘failures of consciousness’. Although stimuli do not reach awareness in these paradigms, there is evidence that they nevertheless undergo semantic processing. Object substitution masking (OSM), however, appears to be the exception to this rule. In OSM, a temporally-trailing four-dot mask interferes with target perception, even though it has different contours from and does not spatially overlap with the target. Previous research suggests that OSM has an early locus, blocking the extraction of semantic information. Here, we refute this claim, showing implicit semantic perception in OSM using a target-mask priming paradigm. We conclude that semantic information suppressed via OSM can nevertheless guide behavior.

Visual masking by object substitution in schizophrenia

Schizophrenia patients demonstrate impairment on visual backward masking, a measure of early visual processing. Most visual masking paradigms involve two distinct processes, an early fast-acting component associated with object formation and a later component that acts through object substitution. So far, masking paradigms used in schizophrenia research have been unable to separate these two processes. We administered three visual processing paradigms (location masking with forward and backward masking, four-dot backward masking and a cuing task) to 136 patients with schizophrenia or schizoaffective disorder and 79 healthy controls. A psychophysical procedure was used to match subjects on identification of an unmasked target prior to location masking. Location masking interrupts object formation, four-dot masking task works through masking by object substitution and the cuing task measures iconic decay. Patients showed impairment on location masking after being matched for input threshold, similar to previous reports. After correcting for age, patients showed lower performance on four-dot masking than controls, but the groups did not differ on the cuing task. Patients with schizophrenia showed lower performance when masking was specific to object substitution. The difference in object substitution masking was not due to a difference in rate of iconic decay, which was comparable in the two groups. These results suggest that, despite normal iconic decay rates, individuals with schizophrenia show impairment in a paradigm of masking by object substitution that did not also involve disruption of object formation.

P29-2 Temporal aspects of object substitution masking studied by transcranial magnetic stimulation

P29-2 Temporal aspects of object substitution masking studied by transcranial magnetic stimulation

Object substitution masking and the object updating hypothesis

The object updating hypothesis of object substitution masking proposes that the phenomenon arises when the visual system fails to individuate target and mask at the level of object token representations. This hypothesis is tested in two experiments using modifications of the dot mask paradigm developed by Lleras and Moore (2003). Target-mask individuation is manipulated by the presentation of additional display items that influence the linking apparent motion seen between a target and a spatially separated mask (Experiment 1), and by the use of placeholders that maintain the target object's presence during mask presentation (Experiment 2). Results in both cases are consistent with the updating hypothesis in showing significantly reduced masking when the conditions promoted target-mask individuation. However, in both experiments, some masking was still present under conditions of individuation, an effect we attribute to attentional capture by the mask.