Motion and position shifts induced by the double-drift stimulus are unaffected by attentional load.

The double-drift stimulus produces a strong shift in apparent motion direction that generates large errors of perceived position. In this study, we tested the effect of attentional load on the perceptual estimates of motion direction and position for double-drift stimuli. In each trial, four objects appeared, one in each quadrant of a large screen, and they moved upward or downward on an angled trajectory. The target object whose direction or position was to be judged was either cued with a small arrow prior to object motion (low attentional load condition) or cued after the objects stopped moving and disappeared (high attentional load condition). In Experiment 1, these objects appeared 10° from the central fixation, and participants reported the perceived direction of the target's trajectory after the stimulus disappeared by adjusting the direction of an arrow at the center of the response screen. In Experiment 2, the four double-drift objects could appear between 6 ° and 14° from the central fixation, and participants reported the location of the target object after its disappearance by moving the position of a small circle on the response screen. The errors in direction and position judgments showed little effect of the attentional manipulation-similar errors were seen in both experiments whether or not the participant knew which double-drift object would be tested. This suggests that orienting endogenous attention (i.e., by only attending to one object in the precued trials) does not interact with the strength of the motion or position shifts for the double-drift stimulus

A snapshot is all it takes to encode object locations into spatial memory

This study examines the encoding of multiple object locations into spatial memory by comparing localization accuracy for stimuli presented at different exposure durations. Participants in the longest duration condition viewed masked displays containing 1-10 discs for 1-10. s (durations typically used in simple span tasks), and then reported the locations of these discs on a blank screen. Compared to conditions that presented the same stimuli briefly for 50 or 200. ms (exposures more typical of simultaneous spatial arrays), localization accuracy did not improve significantly under longer viewing durations. Additionally, a clustering analysis found that responses were spread among different clusters of discs and not focused on individual clusters, regardless of viewing duration. A second experiment tested this performance for displays containing two distinct clusters of discs to determine if clearly grouped subsets of objects would improve performance, but there was no substantial improvement for these two-cluster displays when compared to displays with one cluster. Overall, the results indicate that spatial information for a set of objects is extracted globally and quickly, with little benefit from extended encoding durations that should have favored some deliberative form of grouping. Such results cast doubt on the validity of Corsi blocks or equivalent common neuropsychological tests purportedly designed to evaluate specifically spatial short-term memory spans

Unifying theories of consciousness, attention, and conscious attention

One of the more challenging research areas in cognitive science is the attempt to understand how the brain supports consciousness. This historically philosophical endeavor is now actively studied in the sciences, with research on visual attention being an especially promising area that can further our understanding of consciousness. A major problem with this cross-disciplinary pursuit, however, is that for philosophers and scientists, the terms consciousness, attention, and conscious attention are ambiguous and used differently even by those within the same academic discipline. The goal of this paper is to begin laying the groundwork for a unified study of consciousness by delineating common terminology for attention and consciousness and by identifying the relationship between the two within the study of conscious attention. This includes categorizing current theories according to a spectrum of theoretical complexity

Consciousness, Attention, and Conscious Attention

In this book, Carlos Montemayor and Harry Haladjian consider the relationship between consciousness and attention. The cognitive mechanism of attention has often been compared to consciousness, because attention and consciousness appear to share similar qualities. But, Montemayor and Haladjian point out, attention is defined functionally, whereas consciousness is generally defined in terms of its phenomenal character without a clear functional purpose. They offer new insights and proposals about how best to understand and study the relationship between consciousness and attention by examining their functional aspects. The book’s ultimate conclusion is that consciousness and attention are largely dissociated

Enumerating by pointing to locations : a new method for measuring the numerosity of visual object representations

The fast and accurate enumeration of a small set of objects, called subitizing, is thought to involve a different mechanism from other numerosity judgments, such as those based on estimation. In this report, we examine the subitizing limit using a novel enumeration task that obtained the perceived locations of enumerated objects. Observers were shown brief masked displays (50, 200, and 350 ms) of 2-9 small black discs randomly placed on a gray screen and then asked to place a marker where each disc had been located. The number of these markers provided an estimate of the number of items processed. This "pointing" methodology enabled observers to accurately "enumerate" displays containing up to six items in contrast with the four-item limit typically found when using standard reporting methods (and replicated here in Experiment 2). These results suggest a different account of the limits found in most subitizing and enumeration studies

Evidence for a shared mechanism used in multiple-object tracking and subitizing

It has been proposed that the mechanism that supports the ability to keep track of multiple moving objects also supports subitizing-the ability to quickly and accurately enumerate a small set of objects. To test this hypothesis, we investigated the effects on subitizing when human observers were required to perform a multiple object tracking task and an enumeration task simultaneously. In three experiments, participants (Exp. 1, N = 24; Exp. 2, N = 11; Exp. 3, N = 37) enumerated sets of zero to nine squares that were flashed while they tracked zero, two, or four moving discs. The results indicated that the number of items participants could subitize decreased by one for each item they tracked. No such pattern was seen when the enumeration task was paired with an equally difficult, but nonvisual, working memory task. These results suggest that a shared visual mechanism supports multiple object tracking and subitizing

Spatial compression: Dissociable effects at the time of saccades and blinks

Various studies have identified systematic errors, such as spatial compression, when observers report the locations of objects displayed around the time of saccades. Localization errors also occur when holding spatial representations in visual working memory. Such errors, however, have not been examined in the context of eye blinks. In this study, we examined the effects of blinks and saccades when observers reproduced the locations of a set of briefly presented, randomly placed discs. Performance was compared with a fixation-only condition in which observers simply held these representations in working memory for the same duration; this allowed us to elucidate the relationship between the perceptual phenomena related to blinks, saccades, and visual working memory. Our results indicate that the same amount of spatial compression is experienced prior to a blink as is experienced in the control fixation-only condition, suggesting that blinks do not increase compression above that occurring from holding a spatial representation in visual memory. Saccades, however, tend to increase these compression effects and produce translational shifts both toward and away from saccade targets (depending on the time of the saccade onset in relation to the stimulus offset). A higher numerosity recall capacity was also observed when stimuli were presented prior to a blink in comparison with the other conditions. These findings reflect key differences underlying blinks and saccades in terms of spatial compression and translational shifts. Such results suggest that separate mechanisms maintain perceptual stability across these visual events

Segregating targets and nontargets in depth eliminates inhibition of nontargets in multiple object tracking

Multiple Object Tracking (MOT) is a useful paradigm for studying properties of visual attention. In a typical MOT task, eight or more identical objects are presented on a computer screen. Several of these objects are distinguished as targets by flashing briefly at the beginning of a trial. These objects then move in a random and unpredictable manner, and the observer is asked to identify the targets at the conclusion of this movement (as described in Pylyshyn, 2001; Pylyshyn & Storm, 1988). Observers can easily track four or five objects among identical distractors in a varying range of conditions. Such results have been interpreted as the function of visual indexes (also called FINSTs), which are the preattentive individuation mechanisms proposed by Visual Indexing Theory (Pylyshyn, 2001)

Spatial compression : dissociable effects at the time of saccades and blinks

Various studies have identified systematic errors, such as spatial compression, when observers report the locations of objects displayed around the time of saccades. Localization errors also occur when holding spatial representations in visual working memory. Such errors, however, have not been examined in the context of eye blinks. In this study, we examined the effects of blinks and saccades when observers reproduced the locations of a set of briefly presented, randomly placed discs. Performance was compared with a fixation-only condition in which observers simply held these representations in working memory for the same duration; this allowed us to elucidate the relationship between the perceptual phenomena related to blinks, saccades, and visual working memory. Our results indicate that the same amount of spatial compression is experienced prior to a blink as is experienced in the control fixation-only condition, suggesting that blinks do not increase compression above that occurring from holding a spatial representation in visual memory. Saccades, however, tend to increase these compression effects and produce translational shifts both toward and away from saccade targets (depending on the time of the saccade onset in relation to the stimulus offset). A higher numerosity recall capacity was also observed when stimuli were presented prior to a blink in comparison with the other conditions. These findings reflect key differences underlying blinks and saccades in terms of spatial compression and translational shifts. Such results suggest that separate mechanisms maintain perceptual stability across these visual events

Similarity-dissimilarity competition in disjunctive classification tasks

Typical disjunctive artificial classification tasks require participants to sort stimuli according to rules such as “x likes cars only when black and coupe OR white and SUV.” For categories like this, increasing the salience of the diagnostic dimensions has two simultaneous effects: increasing the distance between members of the same category and increasing the distance between members of opposite categories. Potentially, these two effects respectively hinder and facilitate classification learning, leading to competing predictions for learning. Increasing saliency may lead to members of the same category to be considered less similar, while the members of separate categories might be considered more dissimilar. This implies a similarity-dissimilarity competition between two basic classification processes. When focusing on sub-category similarity, one would expect more difficult classification when members of the same category become less similar (disregarding the increase of between-category dissimilarity); however, the between-category dissimilarity increase predicts a less difficult classification. Our categorization study suggests that participants rely more on using dissimilarities between opposite categories than finding similarities between sub-categories. We connect our results to rule- and exemplar-based classification models. The pattern of influences of within- and between-category similarities are challenging for simple single-process categorization systems based on rules or exemplars. Instead, our results suggest that either these processes should be integrated in a hybrid model, or that category learning operates by forming clusters within each category