Not all summary statistics are made equal: Evidence from extracting summaries across time.

Over the past 15 years, a number of behavioral studies have shown that the human visual system can extract the average value of a set of items along a variety of feature dimensions, often with great facility and accuracy. These efficient representations of sets of items are commonly referred to as summary representations, but very little is known about whether their computation constitutes a single unitary process or if it involves different mechanisms in different domains. Here, we asked participants to report the average value of a set of items presented serially over time in four different feature dimensions. We then measured the contribution of different parts of the information stream to the reported summaries. We found that this temporal weighting profile differs greatly across domains. Specifically, summaries of mean object location (Experiment 1) were influenced approximately 2.5 times more by earlier items than by later items. Summaries of mean object size (Experiment 1), mean facial expression (Experiment 2), and mean motion direction (Experiment 3), however, were more influenced by later items. These primacy and recency effects show that summary representations computed across time do not incorporate all items equally. Furthermore, our results support the hypothesis that summary representations operate differently in different feature domains, and may be subserved by distinct mechanisms.

Rapid and reflexive feature-based attention.

Performance on a visual task is improved when attention is directed to relevant spatial locations or specific visual features. Spatial attention can be directed either voluntarily (endogenously) or automatically (exogenously). However, feature-based attention has only been shown to operate endogenously. Here, we show that an exogenous cue to a visual feature can lead to improved performance in visual search. Response times were measured as subjects detected or discriminated a target oval among an array of disks, each with a unique color. An uninformative colored cue was flashed at the beginning of each trial that sometimes matched the location and/or color of the target oval. Subjects detected or discriminated the target faster when the color of the cue matched the color of the target, regardless of the cue's location relative to the target. Our results suggest evidence for a previously unknown exogenous cuing mechanism for feature-based attention.

Changes in search rate but not in the dynamics of exogenous attention in action videogame players.

Many previous studies have shown that the speed of processing in attentionally demanding tasks seems enhanced following habitual action videogame play. However, using one of the diagnostic tasks for efficiency of attentional processing, a visual search task, Castel and collaborators (Castel, Pratt, & Drummond, Acta Psychologica 119:217-230, 2005) reported no difference in visual search rates, instead proposing that action gaming may change response execution time rather than the efficiency of visual selective attention per se. Here we used two hard visual search tasks, one measuring reaction time and the other accuracy, to test whether visual search rate may be changed by action videogame play. We found greater search rates in the gamer group than in the nongamer controls, consistent with increased efficiency in visual selective attention. We then asked how general the change in attentional throughput noted so far in gamers might be by testing whether exogenous attentional cues would lead to a disproportional enhancement in throughput in gamers as compared to nongamers. Interestingly, exogenous cues were found to enhance throughput equivalently between gamers and nongamers, suggesting that not all mechanisms known to enhance throughput are similarly enhanced in action videogamers.

Stretching the limits of visual attention: the case of action video games.

Visual attention is the set of mechanisms by which relevant visual information is selected while irrelevant information is suppressed, thus allowing the observer to function in a world made up of nearly infinite visual information. Recently, those who habitually play video games have been documented to outperform novices in a variety of visual attentional capabilities, including attention in space, in time, and to objects. Training studies have established similar improvements in groups of nongamers given experience playing these video games. Critically, not all video games seem to have such a beneficial effect on attention; it seems that fast-paced, embodied visuo-motor tasks that require divided attention (tasks commonly found in popular action games like Halo) have the greatest effect. At the core of these action video game-induced improvements appears to be a remarkable enhancement in the ability to efficiently deploy endogenous attention. The implications of such an enhancement are relevant to a variety of real-world applications, such as work force training, rehabilitation of clinical populations, and improvement of traditional educational approaches. WIREs Cogni Sci 2011 2 222-230 DOI: 10.1002/wcs.116 For further resources related to this article, please visit the WIREs website.

Detecting contrast changes in invisible patterns during binocular rivalry.

When dissimilar images are presented to the two eyes, the human visual system lapses into binocular rivalry, a unique perceptual state characterized by stochastic alternations in dominance of one of the two source images over the other. Probe targets delivered to an eye during suppression phases are more difficult to detect than probes delivered during dominance phases. Nearly all probe studies have involved presenting new stimulation (e.g., a spot of light) either superimposed on or replacing the suppressed stimulus. Here, we ask whether observers can detect a reduction in the contrast of the suppressed stimulus itself. In other words, can observers detect a probe that should make an already invisible stimulus even weaker? Specifically, we compared observers' ability to detect contrast increments and contrast decrements introduced within a rival pattern during dominance and suppression. Contrast increment thresholds were elevated across all pedestal contrasts when the increment was introduced during suppression compared to during dominance, replicating previous results. Contrast decrement thresholds measured during suppression were elevated to an even greater extent, but the fact that they were obtained at all establishes that observers were able to detect probes that should make an already invisible target even more difficult to perceive. In a second experiment, we found a similar pattern of results for contrast change detection in complex images of faces as well. Based on the resulting threshold-vs.-contrast functions, we suggest that, regardless of the complexity of the image, rivalry suppression modulates the neural contrast response function through a mixture of reduced overall response gain and a shift in the contrast gain.