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When reading, the visual system is confronted with many words simultaneously. How much of that information can a reader process at once? Previous studies demonstrated that low-level visual features of multiple words are processed in parallel, but lexical attributes are processed serially, for one word at a time. This implies that an internal bottleneck lies somewhere between early visual and lexical analysis. We used a dual-task behavioral paradigm to investigate whether this bottleneck lies at the stage of letter recognition or phonological decoding. On each trial, two letter strings were flashed briefly, one above and one below fixation, and then masked. In the letter identification experiment, participants indicated whether a vowel was present in a particular letter string. In the phonological decoding experiment, participants indicated whether the letter string was pronounceable. We compared accuracy in a focused attention condition, in which participants judged only one of the two strings, with accuracy in a divided attention condition, in which participants judged both strings independently. In both experiments, the cost of dividing attention was so large that it supported a serial model: participants were able to process only one letter string per trial. Furthermore, we found a stimulus processing trade-off that is characteristic of serial processing: When participants judged one string correctly, they were less likely to judge the other string correctly. Therefore, the bottleneck that constrains word recognition under these conditions arises at a sub-lexical level, perhaps due to a limit on the efficiency of letter recognition.

In the rapid serial visual presentation (RSVP) paradigm, response accuracy for the target decreases when it appears within a short time window (200~500 ms) after the previous target. This phenomenon is termed the attentional blink (AB). Although mechanisms of cross-modal processing that reduce the AB have been documented, researchers have not explored the differences across modal attentional conditions. In the present study, we used the RSVP paradigm to investigate the effect of auditory-driven visual target perceptual enhancement on the AB under modality-specific selective attention ( Experiment 1 ) and bimodal-divided attention ( Experiment 2 ). The results showed that cross-modal attentional enhancement was not moderated by stimulus salience. Moreover, the results also showed that accuracy was higher when the attended sound appeared simultaneously with the target. These results indicated that audiovisual enhancement reduced AB and that stronger attentional enhancement in the bimodal-divided attentional condition led to the disappearance of AB.

This study investigated effects of divided attention on the temporal processes of perception. During continuous watch periods, observers responded to sudden changes in the color or direction of any one of a set of moving objects. The set size of moving objects was a primary variable. A simple detection task required responses to any display change, and a selective task required responses to a subset of the changes. Detection rates at successive points in time were measured by response time (RT) hazard functions. The principal finding was that increasing the set size divided the detection rates—and these divisive effects were essentially constant over time and over the time-varying influence of the target signals and response tasks. The set size, visual target signal, and response task exerted mutually invariant influence on detection rates at given times, indicating independent joint contributions of parallel component processes. The lawful structure of these effects was measured by RT hazard functions but not by RTs as such. The results generalized the time-invariant divisive effects of set size on visual process rates found by Lappin, Morse, & Seiffert ( Attention, Perception, & Psychophysics, 78 , 2469–2493, 2016 ). These findings suggest that the rate of visual perception has a limiting channel capacity .

Reading is a demanding task, constrained by inherent processing capacity limits. Do those capacity limits allow for multiple words to be recognized in parallel? In a recent study, we measured semantic categorization accuracy for nouns presented in pairs. The words were replaced by post-masks after an interval that was set to each subject’s threshold, such that with focused attention they could categorize one word with ~80% accuracy. When subjects tried to divide attention between both words, their accuracy was so impaired that it supported a serial processing model: on each trial, subjects could categorize one word but had to guess about the other. In the experiments reported here, we investigated how our previous result generalizes across two tasks that require lexical access but vary in the depth of semantic processing (semantic categorization and lexical decision), and across different masking stimuli, word lengths, lexical frequencies and visual field positions. In all cases, the serial processing model was supported by two effects: (1) a sufficiently large accuracy deficit with divided compared to focused attention; and (2) a trial-by-trial stimulus processing tradeoff, meaning that the response to one word was more likely to be correct if the response to the other was incorrect. However, when the task was to detect colored letters, neither of those effects occurred, even though the post-masks limited accuracy in the same way. Altogether, the results are consistent with the hypothesis that visual processing of words is parallel but lexical access is serial.

When participants respond in the same way to stimuli of two categories, responses are often observed to be faster when both stimuli are presented together (redundant signals) relative to the response time obtained when they are presented separately. This effect is known as the redundant signals effect. Several models have been proposed to explain this effect, including race models and coactivation models of information processing. In race models, the two stimulus components are processed in separate channels, and the faster channel determines the processing time. This mechanism leads, on average, to faster responses to redundant signals. In contrast, coactivation models assume integrated processing of the combined stimuli. To distinguish between these two accounts, Miller ( Cognitive Psychology , 14 , 247–279, 1982 ) derived the well-known race model inequality, which has become a routine test for behavioral data in experiments with redundant signals. In this tutorial, we review the basic properties of redundant signals experiments and current statistical procedures used to test the race model inequality during the period between 2011 and 2014. We highlight and discuss several issues concerning study design and the test of the race model inequality, such as inappropriate control of Type I error, insufficient statistical power, wrong treatment of omitted responses or anticipations, and the interpretation of violations of the race model inequality. We make detailed recommendations on the design of redundant signals experiments and on the statistical analysis of redundancy gains. We describe a number of coactivation models that may be considered when the race model has been shown to fail.

Feature-based attention allocates resources to particular stimulus features and reduces processing and retention of unattended features. We performed four experiments using self-paced video games to investigate whether sustained attentional selection of features could be created without a distractor task requiring continuous processing. Experiments 1 and 2 compared two versions of the game Two Dots , each containing a sequence of images. For the more immersive game post-game recognition of images was very low, but for the less immersive game it was significantly higher. Experiments 3 and 4 found that post-game image recognition was very low if the images were irrelevant to the game task but significantly higher if the images were relevant to the task. We conclude that games create sustained attentional selection away from task-irrelevant features, even if they are in full view, which leads to reduced retention. This reduced retention is due to differences in attentional set rather than a response to limited processing resources. The consistency of this attentional selection is moderated by the level of immersion in the game. We also discuss possible attentional mechanisms for the changes in recognition rates and the implications for applications such as serious games.

After several seconds of adaptation to a visual array of randomly oriented Gabor patterns, observers can detect and localise a change in the orientation of one of these Gabors, even when the change is preceded by a blank inter-stimulus interval. Previously, we reported that the ability to detect this changed element was unaffected by distracting observers’ attention away from the adapting stimuli by making them look for rare conjunctions of shape and colour at the central fixation point. That finding is replicated in the current paper, and augmented by a demonstration of the attentionally demanding nature of the conjunction search: it significantly impairs discrimination between adapting arrays in which either many or few items briefly lose contrast. Consequently, we can be certain of adaptation’s immunity to the withdrawal of attention, when assessed objectively (i.e. with a performance-based metric).

Surreptitious online measures can reveal the processing of stimuli that people do not report noticing or cannot describe. People seem to glean everything from low-level Gestalt grouping information to semantic meaning from unattended and unreported stimuli, and this information seems capable of influencing performance and of priming semantic judgments. Moore and Egeth (Journal of Experimental Psychology: Human Perception and Performance, 23, 339–352, 1997 ) provided evidence that judgments about the lengths of two lines were influenced by the grouping of background dots, even when subjects did not notice the pattern the dots formed. Mack and Rock ( 1998 ) reported that subjects could be primed to complete a stem with a word to which they were inattentionally blind. In this registered report, we replicated these two classic findings using large online samples ( N s = 260 and 448), finding support for the influence of grouping despite inattentional blindness, but not for word-stem priming.

How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct—depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences.

Inattentional blindness, whereby observers fail to detect unexpected stimuli, has been robustly demonstrated in a range of situations. Originally research focused primarily on how stimulus characteristics and task demands affect inattentional blindness, but increasingly studies are exploring the influence of observer characteristics on the detection of unexpected stimuli. It has been proposed that individual differences in working memory capacity predict inattentional blindness, on the assumption that higher working memory capacity confers greater attentional capacity for processing unexpected stimuli. Unfortunately, empirical investigations of the association between inattentional blindness and working memory capacity have produced conflicting findings. To help clarify this relationship, we examined the relationship between inattentional blindness and working memory capacity in two samples ( Ns = 195, 147) of young adults. We used three common variants of sustained inattentional blindness tasks, systematically manipulating the salience of the unexpected stimulus and primary task practice. Working memory capacity, measured by automated operation span (both Experiments 1 & 2 ) and N- back (Experiment 1 only) tasks, did not predict detection of the unexpected stimulus in any of the inattentional blindness tasks tested. Together with previous research, this undermines claims that there is a robust relationship between inattentional blindness and working memory capacity. Rather, it appears that any relationship between inattentional blindness and working memory is either too small to have practical significance or is moderated by other factors and consequently varies with attributes such as the sample characteristics within a given study.