A moving overlay shrinks the attentional blink.

This report describes a study examining the effects of overlaying a veil of spots on the letters in a central rapid serial visual presentation stream. Observers identified two target letters (T1 and T2, respectively) embedded in a stream of distractor letters printed in a different color. In Experiment 1, the attentional blink (AB) diminished when a different overlay veiled each letter, such that the spots appeared to move as the letters changed. Experiment 2 concerned whether the performance enhancement occurred because the overlay hampered processing of the lag 1 distractor, thus weakening the distractor's interference with T1. Experiment 3 focused on how changing the overlay at or around T1 affected the AB. The attention disengagement hypothesis was proposed to explain the common theme in the results-that performance was only enhanced when different overlays were applied to the T1 and lag 1 frames. The claim is that the AB reflects a failure of prompt attentional disengagement from T1, which, in turn, delays reengagement when T2 appears shortly thereafter. When T1's disappearance is accompanied by an overlay change, the perceptual system gets an additional cue signaling that the visual scene has changed, thereby inducing attentional disengagement. Apart from facilitating prompt reengagement at the next target, earlier disengagement also improves target recovery by excluding features of the trailing item, likely to be a distractor, from working memory.

Attentional capture by dynamic cues.

Attention orients to an object that abruptly onsets, because the object's appearance alters the visual scene. In this report, the question was whether there would, similarly, be attentional prioritization of an existing object that changes its dynamic status. Attention may be deployed immediately to the object because its new dynamic status, potentially, also could alter the visual environment. This report focused on the capture capacity of an object--made up of four spots--that abruptly began rotating, thereby endowing it with two dynamic features: motion-onset, apparent when the object transitioned from stationary to moving, and its specific motion trajectory. Because the rotating spots were irrelevant to the main letter-identification task, there ought not to be top-down attentional orienting to them. We asked two questions: (a) whether the rotating object captures attention automatically, and (b) whether both its dynamic features contribute to attentional capture. Four experiments were reported. The observer's attentional set was manipulated by varying, across experiments, the target's diagnostic feature. We examined how the different attentional sets modulated capture. The results showed that the rotating object only succeeded in capturing attention when the attentional system was set to monitor dynamic features.

Tuning characteristics of the top-down attentional setting.

Previous studies of top-down attentional guidance have focused generally on the attentional prioritization of a single target feature. The present study focused on how the attentional system would be configured when the target possesses several unique features. These features were perfectly correlated, which meant that monitoring just one of them would be an adequate strategy. The experiments addressed the following questions: (a) If the target is a singleton, would the attentional system be set to monitor the target's unique features, or would the search strategy default to singleton detection? (b) Can the target's static and dynamic features be prioritized simultaneously? (c) Are all of the target's features prioritized, or only those features that are diagnostic of targethood? The results revealed an attentional system that can be flexibly tuned to multiple target features across static and dynamic dimensions. This system can simultaneously be narrowly tuned to monitor a specific target feature and broadly tuned to detect singletons. Finally, the attentional system monitors only those features that are diagnostic of targethood.

A new object captures attention--but only when you know which objects are old.

According to the new object hypothesis (see, e.g., Yantis & Hillstrom, Journal of Experimental Psychology: Human Perception & Performance, 20, 95-107, 1994), an object appearing as a sudden onset captures attention because its appearance demands an immediate updating of visual short-term memory. This hypothesis was tested in three experiments using a procedure that allowed an object to be added to the display but, crucially, without incurring onset transients (Franconeri, Hollingworth, & Simons, Psychological Science, 16, 275-281, 2005). The latter showed that an object inserted in this fashion failed to capture attention. As a test of the new object hypothesis, this procedure assumes that the observers had encoded the display before the new object was introduced. If this assumption is not fulfilled, the new and the old objects cannot be distinguished one from the other. It was, however, unclear whether the encoding had taken place in the Franconeri et al. experiments. We showed that when circumstances were congenial to the encoding of the display before an additional object interposed, then the object successfully captured attention. But when the encoding of the initial display was either difficult or impossible, the additional object failed to capture attention.

A new object captures attention--but only when you know it's new.

Two hypotheses have been advanced to explain why an object appearing suddenly in an empty location captures attention. According to the first hypothesis, the visual transients that accompany an abrupt onset automatically trigger attentional orienting toward the object. The second hypothesis claims that the visual system regards the onset as an advent of a new object, and the latter's novelty causes attention to be drawn toward it. To discriminate between these two accounts, Franconeri, Hollingworth, and Simons (2005) introduced a procedure in which an object was added to the display but, crucially, the object's onset transients were concealed. Their results showed that this additional object failed to capture attention, which they interpreted as evidence against the new-object hypothesis. But the Franconeri et al. procedure could somehow have impeded the visual system from identifying the additional object as new. In three experiments, Franconeri et al.'s results were first replicated and extended. Further, it was shown that when the conditions facilitated the encoding of the locations of the old items, the new object did succeed in capturing attention.

Object substitution masking: when does mask preview work?

When a target is enclosed by a 4-dot mask that persists after the target disappears, target identification is worse than it is when the mask terminates with the target. This masking effect is attributed to object substitution masking (OSM). Previewing the mask, however, attenuates OSM. This study investigated specific conditions under which mask preview was, or was not, effective in attenuating masking. In Experiment 1, the interstimulus interval (ISI) between previewed mask offset and target presentation was manipulated. The basic preview effect was replicated; neither ISI nor preview duration influenced target identification performance. In Experiment 2, mask configurations were manipulated. When the mask configuration at preview matched that at target presentation, the preview effect was replicated. New evidence of ineffective mask preview was found: When the two configurations did not match, performance declined. Yet, when the ISI between previewed mask offset and target presentation was removed such that the mask underwent apparent motion, preview was effective despite the configuration mismatch. An interpretation based on object representations provides an excellent account of these data.

Capturing focused attention.

When attention is diffuse, as in a visual search task, an abrupt onset almost invariably succeeds in capturing attention. But if attention had been cued in advance to a different location, the same onset may then fail to capture attention (Theeuwes, 1991; Yantis and Jonides, 1990). In previous demonstrations, the onset appeared frequently. This may have diminished the onset's novelty, which in turn could have affected its potency in capturing attention. The question we asked was whether preserving the onset's novelty could enhance its capacity in capturing attention, even when attention had been prioritized elsewhere. As in Theeuwes's (1991) study, observers were cued to the target location with a 100%-predictive central arrow cue. The frequency with which visual transients were introduced was varied across experiments. When the onset stimulus appeared frequently (Experiment 1), it indeed failed to capture attention. But when its appearance was relatively infrequent (Experiment 2), capture effects were clearly observed. In Experiment 3, the target appeared in one location throughout the experiment. This would have improved target localization, but an infrequently appearing onset stimulus still successfully captured attention.

The effect of target contrast on the attentional blink.

In this set of five rapid serial visual presentation experiments, observers identified one or two target letters that were embedded in a stream of distractors. Target contrasts were varied, and their effects on the attentional blink (AB) were examined. Target identification improved when its contrast was increased. But whereas an increase in the first target's (T1) contrast facilitated its identification, the recovery of the second target (T2) was paradoxically hampered (Experiments 2 and 5). Similarly, identification of the target suffered when the preceding singleton's contrast was increased (Experiment 1). The AB was eliminated by inserting a blank after a low-contrast, but not a high-contrast, T1 (Experiment 5). Increasing T2's contrast attenuated the blink (Experiment 3) and compensated the larger AB caused by a high-contrast T1 (Experiment 4). In all, these results showed that attention continued to be engaged as long as the target's contrast prolonged its perceptibility. When the high-contrast target was T1, a larger AB was produced; when it was T2, there was protection from substitution masking.

Capturing attention when attention blinks.

Four experiments addressed the question of whether attention may be captured when the visual system is in the midst of an attentional blink (AB). Participants identified 2 target letters embedded among distractor letters in a rapid serial visual presentation sequence. In some trials, a square frame was inserted between the targets; as the only geometric object in the sequence, it constituted a singleton. Capture effects obtained when the AB was most severe and when it was over were compared. There were 3 main results. First, capture occurred even when the AB was crippling, suggesting that a singleton exogenously engaged attention even when processing of a previous target was continuing apace. Second, when the singleton contained the key target feature, capture effects were clearly manifest. Third, even when the singleton did not possess the key target feature, it still succeeded in capturing attention, although the effects were both feeble and fleeting.

Grouping with and without attention.

The effects of perceptual grouping on a line discrimination task were investigated using Moore and Egeth's (1997) paradigm. Observers judged which of two lines, presented one above the other over a matrix of spots, was longer. On some trials, larger spots at both ends of the lines formed arrowheads, thereby making possible the Müller-Lyer illusion. When observers attended only to the lines, they were not aware of the arrowheads. Yet their line judgment performance showed that they had succumbed to the illusion. When the observers' attention was directed to the arrowheads but they nevertheless failed to discern the arrowheads' orientation, their line judgments were still influenced by the illusion.