Spatial interference between attended items engenders serial visual processing.

A pair of experiments investigated the architecture of visual processing, parallel versus serial, across high and low levels of spatial interference in a divided attention task. Subjects made speeded judgments that required them to attend to a pair of color-cued objects among gray filler items, with the spatial proximity between the attended items varied to manipulate the strength of interference between attended items. Systems factorial analysis (Townsend & Nozawa, Journal of Mathematical Psychology 39:321-359, 1995) was used to identify processing architecture. Experiment 1, using moderately dense displays, found evidence of parallel processing whether attended objects were in low or high proximity to one another. Experiment 2, using higher-density displays, found evidence of parallel selection when attended stimuli were widely separated but serial processing when they were in high proximity. Divided visual attention can operate in parallel under conditions of low or moderate spatial interference between selected items, but strong interference engenders serial processing.

Age, clutter, and competitive selection.

Modern theory explains visual selective attention as a competition for receptive fields in the extrastriate cortex. The present study examined whether this competition contributes to older adults' difficulty in processing visual clutter. In 2 experiments, young and older adult subjects made same-different judgments of target shapes in displays with or without clutter. The target shapes were either high or low in discriminability. The spatial separation between targets varied across trials, and the effects of competitive selection were gauged through decrements in task performance that resulted as separation decreased. Both age groups showed a competition-in-clutter effect, evincing a stronger influence of target separation within cluttered displays. However, the costs of clutter in general and the strength of the competition-in-clutter effect more specifically were both substantially larger for older adults. Effects of clutter and competition also varied with stimulus discriminability; judgments of highly discriminable stimuli evinced no intertarget competition in uncluttered displays for either age group, while judgments of less discriminable stimuli showed competition whether clutter was present or not. Results suggest that clutter disproportionately degrades older adults' visual performance by forcing more careful stimulus resolution, engendering stronger competition for selection.

From classic to current: a look back on attention research in the American Journal of Psychology.

This review examines attention research appearing in The American Journal of Psychology over the journal's rich 125-year history. In particular, the review examines studies focused on selective attention's role in modulating the influence of distraction and the methods used to capture the nature of selective attention. Special attention is given to classic articles by Treisman (1964a, 1964b), Neisser (1963), and Eriksen and Rohrbaugh (1970), whose methods and results are examined in detail in light of current theory and research in selective attention.

Dynamics of target and distractor processing in visual search: evidence from event-related brain potentials.

When multiple objects are present in a visual scene, salient and behaviorally relevant objects are attentionally selected and receive enhanced processing at the expense of less salient or less relevant objects. Here we examined three lateralized components of the event-related potential (ERP) - the N2pc, Ptc, and SPCN - as indices of target and distractor processing in a visual search paradigm. Participants responded to the orientation of a target while ignoring an attentionally salient distractor and ERPs elicited by the target and the distractor were obtained. Results indicate that both the target and the distractor elicit an N2pc component which may index the initial attentional selection of both objects. In contrast, only the distractor elicited a significant Ptc, which may reflect the subsequent suppression of distracting or irrelevant information. Thus, the Ptc component appears to be similar to another ERP component - the Pd - which is also thought to reflect distractor suppression. Furthermore, only the target elicited an SPCN component which likely reflects the representation of the target in visual short term memory.

Event-related potentials dissociate effects of salience and space in biased competition for visual representation.

BACKGROUND: Selective visual attention is the process by which the visual system enhances behaviorally relevant stimuli and filters out others. Visual attention is thought to operate through a cortical mechanism known as biased competition. Representations of stimuli within cortical visual areas compete such that they mutually suppress each others' neural response. Competition increases with stimulus proximity and can be biased in favor of one stimulus (over another) as a function of stimulus significance, salience, or expectancy. Though there is considerable evidence of biased competition within the human visual system, the dynamics of the process remain unknown. METHODOLOGY/PRINCIPAL FINDINGS: Here, we used scalp-recorded electroencephalography (EEG) to examine neural correlates of biased competition in the human visual system. In two experiments, subjects performed a task requiring them to either simultaneously identify two targets (Experiment 1) or discriminate one target while ignoring a decoy (Experiment 2). Competition was manipulated by altering the spatial separation between target(s) and/or decoy. Both experimental tasks should induce competition between stimuli. However, only the task of Experiment 2 should invoke a strong bias in favor of the target (over the decoy). The amplitude of two lateralized components of the event-related potential, the N2pc and Ptc, mirrored these predictions. N2pc amplitude increased with increasing stimulus separation in Experiments 1 and 2. However, Ptc amplitude varied only in Experiment 2, becoming more positive with decreased spatial separation. CONCLUSIONS/SIGNIFICANCE: These results suggest that N2pc and Ptc components may index distinct processes of biased competition--N2pc reflecting visual competitive interactions and Ptc reflecting a bias in processing necessary to individuate task-relevant stimuli.

Competitive interaction degrades target selection: an ERP study.

Localized attentional interference (LAI) occurs when attending to a visual object degrades processing of nearby objects. Competitive interaction accounts of LAI explain the phenomenon as the result of competition among objects for representation in extrastriate cortex. Here, we examined the N2pc component of the event-related potential (ERP) as a likely neural correlate of LAI. In Experiment 1, participants responded to the orientation of a target while ignoring a nearby decoy. At small target-decoy separations, N2pc amplitude was attenuated whereas the amplitude of a later, positive component (Ptc) was potentiated. Experiment 2 ruled out sensory explanations of these effects. The N2pc results are consistent with the idea that spatially mediated competition for representation in extrastriate cortex degrades target selection. Moreover, the Ptc may reflect a bias signal needed to resolve the competition at smaller target-decoy separations.

Localized attentional interference reflects competition for reentrant processing.

Visual performance is compromised when attention is divided between objects that are near one another in the visual field. It has been postulated that this effect, termed localized attentional interference (LAI), reflects competition between visual-object representations for the control of cortical neural responses. To determine whether LAI arises during feedforward processing or during reentrant processing, the present study examined the influence of poststimulus pattern and four-dot masks on the strength of the effect. Experiment 1 found that pattern masks, which are believed to compromise feedforward processing, do not produce stronger LAI than do four-dot masks, which are believed to leave feedforward processing undisrupted. Experiment 2 found that LAI is weaker when reentrant processing is interrupted shortly after initiation than it is when reentrant processing is allowed to run to completion. The results suggest that LAI emerges from competition between objects during reentrant processing.

On the relationship between flanker interference and localized attentional interference.

The flanker interference (FI) effect suggests that visual attention operates like a mental spotlight, enhancing all stimuli within a selected region. In contrast, other data suggest difficulty dividing attention between objects near one another in the visual field, an effect termed localized attentional interference (LAI). The present experiment examined the relationship between these phenomena. Observers made speeded identity judgments of a colored target letter embedded among gray fillers. A response-compatible or -incompatible flanker of a non-target color appeared at varying distances from the target. Data gave evidence of LAI and spatially-graded FI, with mean RTs and flanker effects both decreasing with target-flanker separation. Both effects were reduced when target location was pre-cued and when the target was of higher salience than the flanker. Results suggest that the distribution of spatial attention modulates the strength of objects competing for selection, with this competition underlying both the FI and LAI effects.

Violent video game play impacts facial emotion recognition.

This study assessed the speed of recognition of facial emotional expressions (happy and angry) as a function of violent video game play. Color photos of calm facial expressions morphed to either an angry or a happy facial expression. Participants were asked to make a speeded identification of the emotion (happiness or anger) during the morph. Typically, happy faces are identified faster than angry faces (the happy-face advantage). Results indicated that playing a violent video game led to a reduction in the happy face advantage. Implications of these findings are discussed with respect to the current models of aggressive behavior.

Attentional templates regulate competitive interactions among attended visual objects.

In two experiments, we examined the mechanisms responsible for creating a zone of interference surrounding an attended visual object (see, e.g., Mounts & Gavett, 2004). In Experiment 1, the similarity between attended stimuli and noise items was manipulated in order to contrast an account based on competitive interactions between attended items with an account based on inefficient filtering of unattended stimuli. Consistent with the competitive interaction account, the data revealed that similarity between attended items increased the strength of localized interference, whereas similarity of noise items to the attended stimuli did not. Experiment 2 showed that the interference observed between attended items was determined by their match to attentional templates.

Localized attentional interference affects object individuation, not feature detection.

Modern theorists conceptualize visual selective attention as a competition between object representations for the control of extrastriate receptive fields, an account supported by the finding that attentional selection of one stimulus can degrade processing of nearby stimuli. In the present study the conditions that produce reciprocal interference between attended stimuli are examined. Each display contained either no, one, or two feature-defined target items among an array of homogeneous distractors. Observers performed two tasks, feature detection and object individuation. The feature-detection task required observers to determine if any targets were present within the display. The object-individuation task required observers to determine if the number of targets was exactly two. Spatially mediated interference between target pairs occurred in the object-individuation task, but had no effect on feature detection. Results suggest that localized interference between attended stimuli occurs only when observers are required to resolve the features of individual objects, consistent with the competitive interaction models of attention.

Spatially mediated capacity limits in attentive visual perception.

Modern theories conceptualize visual selective attention as a competition between objects for the control of cortical receptive fields (RFs). Implicit in this framework is the suggestion that spatially proximal objects, which draw from overlapping pools of RFs, should be more difficult to represent in parallel and with excess capacity than spatially separated objects. The present experiments tested this prediction using analysis of response time distributions in a redundant-targets letter identification task. Data revealed that excess-capacity parallel processing is possible when redundant targets are widely separated within the visual field, but that capacity is near fixed when targets are adjacent. Even at the largest separations tested, however, processing capacity remained strongly limited.

Violent media consumption and the recognition of dynamic facial expressions.

This study assessed the speed of recognition of facial emotional expressions (happy and angry) as a function of violent media consumption. Color photos of calm facial expressions morphed to either an angry or a happy facial expression. Participants were asked to make a speeded identification of the emotion (happiness or anger) during the morph. Results indicated that, independent of trait aggressiveness, participants high in violent media consumption responded slower to depictions of happiness and faster to depictions of anger than participants low in violent media consumption. Implications of these findings are discussed with respect to current models of aggressive behavior.

Competition for representation is mediated by relative attentional salience.

The biased competition model of attentional selection proposes that objects compete with one another for neural representation, with the competition rooted in stimulus and attentionally-based salience. Two experiments explore how the salience of a target item relative to flanking items impacts the speed of target identification. The results of two experiments suggest that spatially proximal items compete for shared, spatially dependent processing resources. In both experiments, subjects identified target elements embedded in multi-element displays. In Experiment 1, attentional salience was manipulated by using abrupt onsets (high-salience) and non-onsets (low-salience). Target identifications were slowest when the target was flanked by two high-salience stimuli (abrupt onsets) and fastest when the target was flanked by two low-salience items, (non-onsets). In Experiment 2, the attentional salience of display items was set through a probability manipulation involving the color of the target. The results mirrored those of Experiment 1, consistent with predictions of the biased competition model.

Attentional selection: A salience-based competition for representation.

The role of salience in localized attentional interference (LAI) was examined. In two experiments, target discrimination performance was measured as a function of the spatial separation between the target and a salient distractor item. In Experiment 1, both the salience of the distractor and that of a target were manipulated. Distractor salience was manipulated via size changes to the distractor, and target salience was manipulated by using unmasked or onset targets. When the target was of low salience, the magnitude of interference from the distractor increased with distractor salience. However, when the target had an abrupt onset, the distractor had no impact on target performance. In Experiment 2, the attentional salience of the distractor was manipulated using a probability manipulation. Displays contained both a target and a color singleton distractor. The color singleton produced LAI when it was predictive of the target location but not when it was unpredictive of the target location. The results of both experiments are consistent with models of competition-based attentional selection.

The role of salience in localized attentional interference.

Observers were cued to attend to two discs from an array and made a discrimination of a target presented within one of the discs. In Experiments 1 and 2, the relative attentional salience of the two attended items was manipulated via the cues (size changes in Experiment 1; size and color changes in Experiment 2). In Experiment 3, the relative salience was manipulated via the luminance contrast of the items themselves. In Experiment 4, relative attentional salience was controlled through a probability manipulation. In all experiments, target performance improved with the relative salience of the target, as well as with increased spatial separation between the two items. This localized interference between cued items varied with visual field. Results are discussed in the context of competition-based models of attentional selection.

Age-related differences in localized attentional interference.

Attentional selection of an object in the visual field degrades processing of neighboring stimuli in young adults. A pair of experiments examined the effects of aging on such localized attentional interference. In Experiment 1, younger and older observers made speeded same-different judgments of target shapes that varied in spatial separation. Performance declined for both age groups as the distance between targets decreased, but an Age x Distance interaction indicated that the magnitude of this effect was larger for older adults. Experiment 2 ruled out sensory masking as an explanation for these findings. Results indicate that older observers experience losses in the ability to attend to multiple spatially proximal stimuli within the visual field.