Visual search under physical effort is faster but more vulnerable to distractor interference

Cognition and action are often intertwined in everyday life. It is thus pivotal to understand how cognitive processes operate with concurrent actions. The present study aims to assess how simple physical effort operationalized as isometric muscle contractions affects visual attention and inhibitory control. In a dual-task paradigm, participants performed a singleton search task and a handgrip task concurrently. In the search task, the target was a shape singleton among distractors with a homogeneous but different shape. A salient-but-irrelevant distractor with a unique color (i.e., color singleton) appeared on half of the trials (Singleton distractor present condition), and its presence often captures spatial attention. Critically, the visual search task was performed by the participants with concurrent hand grip exertion, at 5% or 40% of their maximum strength (low vs. high physical load), on a hand dynamometer. We found that visual search under physical effort is faster, but more vulnerable to distractor interference, potentially due to arousal and reduced inhibitory control, respectively. The two effects further manifest in different aspects of RT distributions that can be captured by different components of the ex-Gaussian model using hierarchical Bayesian method. Together, these results provide behavioral evidence and a novel model for two dissociable cognitive mechanisms underlying the effects of simple muscle exertion on the ongoing visual search process on a moment-by-moment basis.

Attentional Templates Are Sharpened through Differential Signal Enhancement, Not Differential Allocation of Attention

In visual search, the internal representation of the target feature is referred to as attentional template. The attentional template can be broad or precise depending on the task requirements. In singleton search, the attentional template is broad because the target is the only colored element in the display. In feature search, a precise attentional template is required because the target is in a specific color in an array of varied colors. To measure the precision of the attentional template, we used a cue-target paradigm where cueing benefits decrease when the cue color differs from the target color. Consistent with broad and precise attentional templates, the decrease of cueing effects was stronger in feature than in singleton search. Measurements of ERPs showed that the N2pc elicited by the cue decreased with increasing color difference, suggesting that attention was more strongly captured by cues that were similar to the target. However, the cue-elicited N2pc did not differ between feature and singleton search, making it unlikely to reflect the mechanism underlying attentional template precision. Furthermore, there was no evidence for attentional suppression as there was no cue-elicited PD, even in conditions where the cueing benefit turned into a same-location cost. However, an index of signal enhancement, the contralateral positivity, reflected attention template precision. In general, there was sensory enhancement of the stimulus appearing at the cued location in the search display. With broad attentional templates, any stimulus at the cued location was enhanced, whereas enhancement was restricted to target-matching colors with precise attentional templates.

A quantitative analysis of the taxonomy of artistic styles

Classifying artists and their work as distinct art styles has been an important task of scholars in the field of art history. Due to its subjectivity, scholars often contradict one another. Our project investigated differences in aesthetic qualities of seven art styles through quantitative means. This was achieved with state-of-the-art deep-learning paradigms to generate new images resembling the style of an artist or entire era. We conducted psychological experiments to measure the behavior of subjects when viewing these new art images. Two different experiments were used: In an eye-tracking study, subjects viewed art-style-specific generated images. Eye movements were recorded and then compared between art styles. In a visual singleton search study, subjects had to locate a style-outlier image among three images of an alternative style. Reaction time and accuracy were measured and analyzed. These experiments show that there are measurable differences in behavior when viewing images of varying art styles. From these differences, we constructed hierarchical clusterings relating art styles based on the different behaviors of subjects viewing the samples. Our study reveals a novel perspective on the classification of artworks into stylistic eras and motivates future research in the domain of empirical aesthetics through quantitative means.

The influence of display-to-display feature changes on net cueing effects: Evidence for a contribution of object-file updating

In spatial cueing, presenting a peripheral cue at the same position as a to-be-searched-for target (valid condition) facilitates search relative to a cue presented away from the target (invalid condition). It is assumed that this cueing effect reflects spatial attentional capture to the cued position that facilitates search in valid relative to invalid conditions. However, the effect is typically stronger for top-down matching cues that resemble the targets than for non-matching cues that are different from targets. One factor which could contribute to this effect is that in valid non-matching conditions, a cue-to-target colour difference could prompt an object-updating cost of the target that counteracts facilitative influences of attention capture by the valid cues (this has been shown especially in known-singleton search). We tested this prediction by introducing colour changes at target locations in valid and invalid conditions in feature search. This should compensate for selective updating costs in valid conditions and unmask the true capture effect of non-matching cues. In addition, in top-down matching conditions, colour changes at target positions in invalid conditions should increase the cueing effect, now by selective updating costs in addition to capture away from the targets in invalid conditions. Both predictions were borne out by the results, supporting a contribution of object-file updating to net cueing effects. However, we found little evidence for attentional capture by non-matching cues in feature search even when the selective cost by object-file updating in only valid conditions was compensated for.

Attentional Access to Multiple Target Objects in Visual Search

Most investigations of visual search have focused on the discrimination between a search target and other task-irrelevant distractor objects (selection). The attentional limitations that arise when multiple target objects in the same display have to be processed simultaneously (access) remain poorly understood. Here, we employed behavioral and electrophysiological measures to investigate the factors that determine whether multiple target objects can be accessed in parallel. Performance and N2pc components were measured for search displays that contained either a single target or two target objects. When two target objects were present, they either had the same or different target-defining features. Participants reported whether search displays contained a single target, two targets with shared features, or two targets with different features. There were performance costs as well as reduced N2pc amplitudes for two-target/different relative to two-target/same displays, suggesting that access to multiple target objects defined by different features was impaired. These behavioral and electrophysiological costs were also observed in a task where all search display objects were physically different, but not during color or shape singleton search, confirming that they do not reflect a low-level perceptual grouping of physically identical targets. These results demonstrate strong feature-specific limitations of visual access, as proposed by the Boolean map theory of visual attention. They suggest that multiple target objects can be accessed in parallel only when they share task-relevant features and demonstrate that mechanisms of visual access can be studied with electrophysiological markers.

Expectations and perceptual priming in a visual search task: Evidence from eye movements and behavior

An extensive amount of research indicates that repeating target and distractor features facilitates pop-out search while switching these features slows the search. Following the seminal study by Maljkovic & Nakayama (1994), this ‘priming of pop-out’ effect (PoP) has been widely described as an automatic bottom-up process that is independent of the observers' expectations. At the same time, numerous studies emphasize the crucial role of expectations in visual attention deployment. Our experiment shows that in contrast to previous claims, PoP in a classic color singleton search task is a mix of automatic priming and expectations. Participants searched for a uniquely-colored diamond among two same-colored distractors. Target color sequences were either predictable (e.g., two red-target-green-distractors trials, followed by two green-target-red- distractors trials, and so on) or random. Responses were faster in predictable color sequences than randomly changing ones with equal number of repetitions of target colors on preceding trials. Analysis of observers’ eye movements showed that predictability of target color affected both latency and accuracy of the first saccade during a search trial. Our results support the idea that PoP is governed not only by automatic effects from previous target or distractor features but also by top-down expectations.

Search for Capacity-Limited and Super-Capacity Search

The present study investigated capacity limitations of visual search. In a series of experiments, participants searched for a singleton target among homogenous distractors, a conjunction target defined by combination of two features, or a feature target among heterogeneous distractors. Using the simultaneous-sequential paradigm, I found that singleton search proceeded in a capacity-unlimited manner. By contrast, the performance of the conjunction search was found to depend on a capacity-limited process. For feature searches, the performance of searching for a specific color was not affected by how the stimuli were presented, while the orientation search performance was enhanced as the number of distractors simultaneously presented with the target increased. These results imply that distinct colors are individually coded, whereas multiple orientations are encoded as an ensemble in a structured way. Taken together, the present study clarifies which type of search process are capacity-limited and reveals how this limit can be overcome.