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.

Perception and Cognition Are Largely Independent, but Still Affect Each Other in Systematic Ways: Arguments from Evolution and the Consciousness-Attention Dissociation.

The main thesis of this paper is that two prevailing theories about cognitive penetration are too extreme, namely, the view that cognitive penetration is pervasive and the view that there is a sharp and fundamental distinction between cognition and perception, which precludes any type of cognitive penetration. These opposite views have clear merits and empirical support. To eliminate this puzzling situation, we present an alternative theoretical approach that incorporates the merits of these views into a broader and more nuanced explanatory framework. A key argument we present in favor of this framework concerns the evolution of intentionality and perceptual capacities. An implication of this argument is that cases of cognitive penetration must have evolved more recently and that this is compatible with the cognitive impenetrability of early perceptual stages of processing information. A theoretical approach that explains why this should be the case is the consciousness and attention dissociation framework. The paper discusses why concepts, particularly issues concerning concept acquisition, play an important role in the interaction between perception and cognition.

The thalamus as a relay station and gatekeeper: relevance to brain disorders.

Here, we provide a review of behavioural, cognitive, and neural studies of the thalamus, including its role in attention, consciousness, sleep, and motor processes. We further discuss neuropsychological and brain disorders associated with thalamus function, including Parkinson's disease, Alzheimer's disease, Korsakoff's syndrome, and sleep disorders. Importantly, we highlight how thalamus-related processes and disorders can be explained by the role of the thalamus as a relay station.

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.

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.

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 lesssimilar, while the members of separate categories might be considered moredissimilar. 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.

A content analysis of Web sites promoting smoking culture and lifestyle.

The present study examined smoking culture and lifestyle Web sites listed on Yahoo!, a popular Internet search catalog, to determine whether the sites were easily accessible to youth, featured age or health warnings, and mentioned specific tobacco brands. A content analysis of photographs on these sites assessed the demographics of individuals depicted and the amount of smoking and nudity in the photographs. The sample included 30 Web sites, all of which were accessible to youth and did not require age verification services to enter them. Cigarette brand names were mentioned in writing on 35% of the sites, and brand images were present on 24% of the sites. Nearly all of the photographs (95%) depicted smoking, 92% featured women, and 7% contained partial or full nudity. These results underscore the need for greater research and monitoring of smoking-related Internet content by health educators and tobacco control advocates.