Attentional episodes in visual perception

Is one's temporal perception of the world truly as seamless as it appears? This article presents a computationally motivated theory suggesting that visual attention samples information from temporal episodes (episodic simultaneous type/serial token model; Wyble, Bowman, & Nieuwenstein, 2009). Breaks between these episodes are punctuated by periods of suppressed attention, better known as the attentional blink (Raymond, Shapiro, & Arnell, 1992). We test predictions from this model and demonstrate that participants were able to report more letters from a sequence of 4 targets presented in a dense temporal cluster than from a sequence of 4 targets interleaved with nontargets. However, this superior report accuracy comes at a cost in impaired temporal order perception. Further experiments explore the dynamics of multiple episodes and the boundary conditions that trigger episodic breaks. Finally, we contrast the importance of attentional control, limited resources, and memory capacity constructs in the model.     

Task-irrelevant visual motion and flicker attenuate the attentional blink

Our reduced ability to correctly report two sequentially presented targets is seen in the robust effect known as the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992). One recent report (Olivers & Nieuwenhuis, 2005) strikingly reveals the AB to be virtually abolished when non-task-demanding music occurs in the background. The authors suggest that a diffuse attentional state is the mediating factor. Here, we seek to broaden the finding’s generality by determining if task-irrelevant visual motion and flicker also attenuate the AB. In our experiments, the AB task was presented together with a background field of moving dots that could moveaway from ortoward the central AB task, or flicker. In the control condition, the dots remained static. The AB was attenuated—though to different degrees—in all experimental conditions, but not in the static condition. Our findings add to the generality of the previous conclusions, and we emphasize an account based on the overallocation of attention.     

Perception of temporal order is impaired during the time course of the attentional blink

Identification accuracy for the second of two target (T2) is impaired when presented shortly after the first (T1). Does this attentional blink (AB) also impair the perception of the order of presentation? In four experiments, three letter targets (T1, T2, T3) were inserted in a stream of digit distractors displayed in rapid serial visual presentation (RSVP), with T3 always presented directly after T2. The T1-T2 lag was varied to assess the perception of T2-T3 temporal order throughout the period of the AB. Factorial manipulation of the presence or absence of distractors before T1 and between T1 and T2 had similar effects on accuracy and on perception of temporal order. It is important to note that perception of temporal order suffered even when accuracy was unimpaired. This pattern of results is consistent with prior-entry theories of the perception of temporal order but not with episodic-integration theories. Simulations based on the Episodic Simultaneous Type, Serial Token (eSTST) model (Wyble, Bowman, & Nieuwenstein, 2009) provided excellent fits to the data except for the condition in which no distractors were presented in the RSVP stream.     

Representational masking and the attentional blink

After successful detection of a target item within a stream of rapidly displayed visual stimuli, subsequent detection of an additional target is impaired for roughly 500 ms. This impairment is known as the “attentional blink” (AB). Previous studies have found that if either the first (Tl; Raymond, Shapiro, & Arnell, 1992) or second target (T2; Giesbrecht & Di Lollo, 1998) is not followed by a mask, the AB impairment is significantly reduced. Whereas low-level perceptual factors have been found to influence the efficacy of masking in the AB (e.g., Seiffert & Di Lollo, 1997), the current experiment used a higher level (representational) manipulation, i.e., repetition blindness to reduce the efficacy of target masking in the AB. These findings contribute to the growing literature suggesting that masking plays more than a perceptual role in the AB phenomenon.     

The attentional blink reflects retrieval competition among multiple rapid serial visual presentation items: tests of an interference model

When people respond to a target (T1) in a rapid serial visual presentation stream, their perception of a subsequent target (T2) is impaired if the intertarget stimulus onset asynchrony is between about 100 and 500 ms. Three experiments supported the interference model's (K. L. Shapiro, J. E. Raymond, & K. M. Arnell, 1994) claim that this attentional blink reflects competition for retrieval among multiple items in visual short-term memory. Experiments 1 and 2 revealed that items appearing during the blink are named as T2 on an above-chance proportion of trials when T2 must be identified. Experiment 3 demonstrated that both the size of the blink and sensitivity to T2 reflected the number of items competing for retrieval as T2; such competition, moreover, occurred at a conceptual or categorical level rather than at a purely visual one. The relationship between the interference and alternative models of the attentional blink is discussed.     

Visual, auditory, and cross-modality dual-task costs: electrophysiological evidence for an amodal bottleneck on working memory consolidation

When two masked, attended targets (T1 and T2) are presented within approximately half a second of each other, report of T2 is poor, compared with when the targets are presented farther apart in time--a phenomenon known as the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992). Some researchers have suggested that an amodal bottleneck on working memory consolidation underlies the AB (see, e.g., Arnell & Jolicoeur, 1999). In the present work, T1 was masked, whereas T2 was unmasked. The modality of T1 (visual or auditory) and the modality of T2 (visual or auditory) were factorially manipulated across four experiments. For all modality combinations, T2's P3 event-related brain potential component was found to be delayed when T2 was presented soon after T1 (lag 3), compared with when T1 and T2 were presented farther apart (lag 8). Results suggest that the working memory consolidation bottleneck is amodal in nature, and provide evidence that visual, auditory, and cross-modality ABs all result from a bottleneck on consolidation operations.     

Delayed masking and the auditory attentional blink: A test for retrieval competition and bottleneck models

The attentional blink (AB) corresponds to a transient deficit in reporting the second (T2) of two targets embedded in a rapid sequence of distractors. The retrieval competition (Shapiro, Raymond & Arnell, 1994) and bottleneck models (Chun & Potter, 1995; Jolicoeur, 1998) predict the attenuation of the deficit with the extension of the delay between T2 and its mask. This prediction was tested using auditory sequences of nonverbal stimuli in which the T2-mask interval was systematically varied. The magnitude of the auditory AB diminished with the lengthening of the interval from 50 to 150 ms while no time-locked deficit was observed with the longest (350 ms) and the shortest (10 ms) intervals. These results suggest that presenting a mask after T2 is not sufficient to produce an auditory AB: The mask must be perceivable as an auditory event distinct from the target and occur before T2 consolidation. The present study also provides evidence that as in vision, AB deficits take place in the auditory domain when T2 is masked by interruption but not by integration. Our findings are best accounted for in terms of bottlenecked processing limitations.     

Attentional blink differences between adolescent dyslexic and normal readers

The goal of this study was to evaluate the possibility that dyslexic individuals require more working memory resources than normal readers to shift attention from stimulus to stimulus. To test this hypothesis, normal and dyslexic adolescents participated in a Rapid Serial Visual Presentation experiment (Raymond, Shapiro, & Arnell, 1992). Surprisingly, the result showed that the participants with dyslexia produced a shallower attentional blink than normal controls. This result may be interpreted as showing differences in the way the two groups encode information in episodic memory. They also fit in a cascade-effect perspective of developmental dyslexia.     

Age Differences in the Magnitude of the Attentional Blink

When people attend to a target in a rapid sequence of items, their perception of a subsequent target is impaired for about 500 ms. This is termed the attentional blink. In the present experiment, a dual task rapid serial presentation task (Raymond, Shapiro & Arnell, 1992) was used as a measure of inhibitory function of younger and older adults. We found that the attentional blink was larger among older adults as compared to younger adults, supporting Hasher and Zacks' (1988) inhibitory deficit hypothesis and current models of the attentional blink.     

The root cause of the attentional blink: First-target processing or disruption of input control?

Identification of the second of two targets (T2) is impaired when presented shortly after the first (T1). T1-based theories ascribe this attentional blink (AB) to a T1-initiated period of inattention. Distractor-based theories ascribe it to a disruption of input control caused by post-T1 distractors. The finding that an AB occurs without intertarget distractors (Nieuwenstein, Potter, & Theeuwes, Journal of Experimental Psychology: Human Perception and Performance 35:159-169, 2009) seemingly disconfirms distractor-based theories. The present experiments addressed different ways in which distractor-based theories might account for that finding. Intertarget events were varied in four experiments. Experiment 1 replicated Nieuwenstein, Potter, and Theeuwes??s findings. The next two experiments tested two ways (lack of visual stimulation, violation of expectation) in which the blank intertarget interval might cause an AB. Experiment 4 explored whether backward-masking of T1 can account entirely for the larger AB obtained with intervening distractors or whether distractors also disrupt input control. The results disconfirm predictions from distractor-based theories and support the claim of T1-based theories that T1 processing alone is sufficient for the AB. Simulations based on the eSTST (Wyble, Bowman, & Nieuwenstein, Journal of Experimental Psychology: Human Perception and Performance 35:787-807, 2009) and the B&B models (Olivers & Meeter, Psychological Research, 115, 836-863 2008) were compared. Predictions were more accurate from the T1-based theory (eSTST) than from the distractor-based theory (B&B).     

Affective states leak into movement execution: Automatic avoidance of threatening stimuli in fear of spider is visible in reach trajectories

Several studies have shown that the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992) is diminished for highly arousing T2 stimuli (e.g., Anderson, 2005). Whereas this effect is most often interpreted as evidence for a more efficient processing of arousing information, it could be due also to a bias to report more arousing stimuli than neutral stimuli. We introduce a paradigm that allows one to control for such a response bias. Using this paradigm, we obtained evidence that the diminished AB for taboo words cannot be explained by a response bias. This supports the idea that the emotional modulation of the AB is caused by attentional processes.     

Is the emotional modulation of the attentional blink driven by response bias?

Several studies have shown that the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992) is diminished for highly arousing T2 stimuli (e.g., Anderson, 2005). Whereas this effect is most often interpreted as evidence for a more efficient processing of arousing information, it could be due also to a bias to report more arousing stimuli than neutral stimuli. We introduce a paradigm that allows one to control for such a response bias. Using this paradigm, we obtained evidence that the diminished AB for taboo words cannot be explained by a response bias. This supports the idea that the emotional modulation of the AB is caused by attentional processes.     

Beyond similarity: Masking of the target is sufficient to cause the attentional blink

When subjects are asked to identify a letter target embedded in a rapid serial visual presentation stream, the detection of a subsequent letter probe is briefly impaired. This transient deficit in probe detection, termed the “attentional blink,” depends on the type of item that immediately follows the letter target (Raymond, Shapiro, & Arnell, 1995). Two models have been proposed to account for this effect. The interference model of the attentional blink predicts that visual similarity between the probe and item immediately following the target (+1 item) causes the attentional blink, whereas the two-stage model is based on the notion that increased time needed to process the target letter causes the attentional blink. In order to test between these two possibilities, the masking properties of the +1 item and its similarity to the probe were varied. We found the attentional blink when the +1 item acted as a mask of the target, even though the +1 item and the probe were visually dissimilar. This pattern of results supports the two-stage model of the attentional blink.     

Top-down controlled, delayed selection in the attentional blink

In a previous study, it was shown that the attentional blink (AB)--the failure to recall the 2nd of 2 visual targets (T1 and T2) presented within 500 ms in rapid serial visual presentation--is reduced when T2 is preceded by a distractor that shares a feature with T2 (e.g., color; Nieuwenstein, Chun, van der Lubbe & Hooge, 2005). Here, this cuing effect is shown to be contingent on attentional set. For example, a red distractor letter preceding a green digit T2 is an effective cue when the task is to look for red and green digits, but the same red cue is relatively ineffective when the task is to look for only green digits or when the color of T2 is not specified. It is also shown that cuing is not interrupted by a distractor intervening between the cue and T2. These findings provide evidence for a contingent, delayed selection account of the AB.     

Attentional and perceptual sources of the auditory attentional blink

When a rapid succession of auditory stimuli is listened to, processing of the second of two successive targets among fillers is often impaired, a phenomenon known as the attentional blink (AB). Three experiments were conducted to examine the role of filler items in modulating the size of the auditory AB, using a two-alternative forced choice discrimination paradigm. In the first experiment, dual-stream presentations in which low- and high-pitch items were separated by six semitones were tested. A transient deficit in reporting the probe was observed in the presence of fillers that was greater when fillers were in the same stream as the probe. In the absence of a filler, there was a residual deficit, but this was not related to the time lag between the target and the probe. In the second and third experiments, in which single-stream presentations were used, a typical AB was found in the presence of homogeneous fillers, but heterogeneous fillers tended to produce a greater deficit. In the absence of a filler, there was little or no evidence of a blink. The pattern of results suggests that other attentional and perceptual factors contribute to the blink.     

An attentional blink for sequentially presented targets: Evidence in favor of resource depletion accounts

Several accounts of the attentional blink (AB) have postulated that this dual-target deficit occurs because of limited-capacity attentional resources being devoted to processing the first target at the expense of the second (resource depletion accounts; e.g., Chun & Potter, 1995). Recent accounts have challenged this model (e.g., Di Lollo, Kawahara, Ghorashi, & Enns, 2005; Olivers, van der Stigchel, & Hulleman, 2007), proposing instead that the AB occurs because of subjects’ inability to maintain appropriate levels of attentional control when targets are separated by distractors. Accordingly, the AB is eliminated when three targets from the same attentional set are presented sequentially in a rapid serial visual presentation (RSVP) stream. However, under such conditions poorer identification of the first target is typically observed, hinting at a potential trade-off between the first and subsequent target performances. Consistent with this hypothesis, the present study shows that an AB is observed for successive targets from the same attentional set in an RSVP stream when the first target powerfully captures attention. These results suggest that resource depletion contributes significantly to the AB.     

The attentional blink with targets in different spatial locations

When two targets (T1 and T2) are displayed in rapid succession, accuracy of T2 identification varies as a function of the temporal lag between the targets (attentional blink, AB). In some studies, performance has been found to be most impaired at Lag 1—namely, when T2 followed T1 directly. In other studies, T2 performance at Lag 1 has been virtually unimpaired (Lag 1 sparing). In the present work, we examined how Lag 1 sparing is affected by attentional switches between targets displayed in the same location or in different locations. We found that Lag 1 sparing does not occur when a spatial shift is required between T1 and T2. This suggests that attention cannot be switched to a new location while the system is busy processing another stimulus. The results are explained by a modified version of an attentional gating model (Chun & Potter, 1995; Shapiro & Raymond, 1994).     

The role of observer strategy in the single-target AB paradigm

Identification of the second of two targets (T1, T2) inserted in a stream of distractors is impaired when presented 200–500 ms after the first (attentional blink, AB). An AB-like effect has been reported by Nieuwenstein, Potter, and Theeuwes, Journal of Experimental Psychology: Human Perception and Performance, 35, 159-169, (2009, Experiment 2), with a distractor stream that contained only one target and a gap just before the target. Nieuwenstein et al. hypothesized that the gap enhanced the salience of the last distractor, causing it to be processed much like T1 in conventional AB studies. This hypothesis can also account for Lag-1 sparing (enhanced target performance when presented directly after the last distractor, without an intervening gap). We propose an alternative account of the Lag-1 sparing in the single-target paradigm based on observer strategy, and test it by presenting the single-target and dual-target conditions to separate groups (Experiment 2) instead of mixed across trials (Experiment 1 and Nieuwenstein et al.'s study). The single-target condition exhibited Lag-1 sparing when it was mixed with the dual-target condition, but Lag-1 deficit when it was done in isolation. This outcome is consistent with an observer-strategy account but not with an enhanced salience account of the Lag-1 sparing effect in the single-target condition.     

Sources of interference in the attentional blink: target-distractor similarity revisited

Observers monitored streams of words or letters (10 items/sec) for one or two targets. An attentional blink (AB) effect was observed in which identification of the first target temporarily impaired identification of the second target. Target identification was impaired when the distractors were composed of either letters or false-font characters (cf. Maki, Couture, Frigen, & Lien, 1997). An asymmetrical AB effect was observed with letters and mathematical symbols; the AB effect was largest for symbol targets and letter distractors. The characters used in these experiments were rated on their meaningfulness, familiarity, and other stimulus properties. The rating data showed that pixel density best accounted for the asymmetrical target-distractor similarity effects. Modulation of the AB effect by target-distractor similarity appears to result partly from low-level masking. But masking effects may be reduced by attentional capture by target features.     

Object file continuity predicts attentional blink magnitude

When asked to identify targets embedded within a rapid consecutive stream of visual stimuli, observers are less able to identify the second target (T2) when it is presented within half a second of the first (T1); this deficit has been termed the attentional blink (AB). Rapid serial visual presentation methodology was used to investigate the relationship between the AB and object files (episodic representations implicated in object identification and perceptual constancy). An inverse linear relationship was found between the degree of object file continuity and AB magnitude. An important locus of object file continuity was the intervening stream items between T1 and T2. The results are discussed in terms of the heuristic of the object file to preserve limited attentional capacity.