Background: Neurotypical young adults show task-based modulation and stability of their eye movements across tasks. This study aimed to determine whether persons with aphasia (PWA) modulate their eye movements and show stability across tasks similarly to control participants. Methods: Forty-eight PWA and age-matched control participants completed four eye-tracking tasks: scene search, scene memorization, text-reading, and pseudo-reading. Results: Main effects of task emerged for mean fixation duration, saccade amplitude, and standard deviations of each, demonstrating task-based modulation of eye movements. Group by (...) task interactions indicated that PWA produced shorter fixations relative to controls. This effect was most pronounced for scene memorization and for individuals who recently suffered a stroke. PWA produced longer fixations, shorter saccades, and less variable eye movements in reading tasks compared to controls. Three-way interactions of group, aphasia subtype, and task also emerged. Text-reading and scene memorization were particularly effective at distinguishing aphasia subtype. Persons with anomic aphasia showed a reduction in reading saccade amplitudes relative to their respective control group and other PWA. Persons with conduction/Wernicke’s aphasia produced shorter scene memorization fixations relative to controls or PWA of other subtypes, suggesting a memorization specific effect. Positive correlations across most tasks emerged for fixation duration and did not significantly differ between controls and PWA. Conclusions: PWA generally produced shorter fixations and smaller saccades relative to controls particularly in scene memorization and text-reading respectively. The effect was most pronounced recently after a stroke. Selectively in reading tasks, PWA produced longer fixations and shorter saccades relative to controls, consistent with reading difficulty. PWA showed task-based modulation of eye movements, though the pattern of results was somewhat abnormal relative to controls. All subtypes of PWA also demonstrated task-based modulation of eye movements. However, persons with anomic aphasia showed reduced modulation of saccade amplitude and smaller reading saccades, possibly to improve reading comprehension. Controls and PWA generally produced stabile fixation durations across tasks and did not differ in their relationship across tasks. Overall, these results suggest there is potential to differentiate among PWA with varying subtypes and from controls using eye movement measures of task-based modulation, especially reading and scene memorization tasks. (shrink)

The question regarding how to characterize aesthetics has been revived with the publication of Bence Nanay’s _Aesthetics as Philosophy of Perception_. This paper takes seriously Dustin Stokes’ criticisms of Nanay’s book regarding Nanay’s inability to distinguish between ordinary expert visual tasks (e.g., sorting for sock color or ornithology) and aesthetic experience. Using empirical research on gist perception and its reliance on low-level features in visual experience, I develop a theory that distinguishes expert visual tasks and aesthetic experiences by differentiating two (...) different kinds of distributed attention over properties. I argue that expert visual tasks are instances of property attribution in a mode of conscious attention, while aesthetics is a kind of distributed attention that significantly relies on the reiteration of gist-like lowlevel features. Gist, often referred to in visual science as “preattentive” mode, gives us a model to understand the perceptual processes that are specific to aesthetics. This comports with our common-sense definition of aesthetics as both distinguishable from ordinary expert visual tasks and an experience that makes prominent sensory aspects of visual experience. (shrink)

The process of urban landmark-based navigation has proven to be difficult to study in a rigorous fashion, primarily due to confounding variables and the problem of obtaining reliable data in real-world contexts. The development of high-resolution, immersive virtual reality technologies has opened exciting new possibilities for gathering data on human wayfinding that could not otherwise be readily obtained. We developed a research platform using a virtual environment and electroencephalography to better understand the neural processes associated with landmark usage and recognition (...) during urban navigation tasks. By adjusting the architectural parameters of different buildings in this virtual environment, we isolated and tested specific design features to determine whether or not they served as a target for landmarking. EEG theta band event-related synchronization/desynchronization over posterior scalp areas was evaluated at the time when participants observed each target building along a predetermined self-paced route. A multi-level linear model was used to investigate the effects of salient architectural features on posterior scalp areas. Our results support the conclusion that highly salient architectural features—those that contrast sharply with the surrounding environment—are more likely to attract visual attention, remain in short-term memory, and activate brain regions associated with wayfinding compared with non-salient buildings. After establishing this main aggregate effect, we evaluated specific salient architectural features and neural correlates of navigation processing. The buildings that most strongly associated extended gaze time, location recall accuracy, and changes in theta-band neural patterns with landmarking in our study were those that incorporated rotational twist designs and natural elements such as trees and gardens. Other building features, such as unusual façade patterns or building heights, were to a lesser extent also associated with landmarking. (shrink)

Understanding how people comprehend visual narratives (including picture stories, comics, and film) requires the combination of traditionally separate theories that span the initial sensory and perceptual processing of complex visual scenes, the perception of events over time, and comprehension of narratives. Existing piecemeal approaches fail to capture the interplay between these levels of processing. Here, we propose the Scene Perception & Event Comprehension Theory (SPECT), as applied to visual narratives, which distinguishes between front-end and back-end cognitive processes. Front-end processes occur (...) during single eye fixations and are comprised of attentional selection and information extraction. Back-end processes occur across multiple fixations and support the construction of event models, which reflect understanding of what is happening now in a narrative (stored in working memory) and over the course of the entire narrative (stored in long-term episodic memory). We describe relationships between front- and back-end processes, and medium-specific differences that likely produce variation in front-end and back-end processes across media (e.g., picture stories vs. film). We describe several novel research questions derived from SPECT that we have explored. By addressing these questions, we provide greater insight into how attention, information extraction, and event model processes are dynamically coordinated to perceive and understand complex naturalistic visual events in narratives and the real world. (shrink)

This study investigates to what extent the amount of variation in a visual scene causes speakers to mention the attribute color in their definite target descriptions, focusing on scenes in which this attribute is not needed for identification of the target. The results of our three experiments show that speakers are more likely to redundantly include a color attribute when the scene variation is high as compared with when this variation is low (even if this leads to overspecified descriptions). We (...) argue that these findings are problematic for existing algorithms that aim to automatically generate psychologically realistic target descriptions, such as the Incremental Algorithm, as these algorithms make use of a fixed preference order per domain and do not take visual scene variation into account. (shrink)

When producing a description of a target referent in a visual context, speakers need to choose a set of properties that distinguish it from its distractors. Computational models of language production/generation usually model this as a search process and predict that the time taken will increase both with the number of distractors in a scene and with the number of properties required to distinguish the target. These predictions are reminiscent of classic findings in visual search; however, unlike models of reference (...) production, visual search models also predict that search can become very efficient under certain conditions, something that reference production models do not consider. This paper investigates the predictions of these models empirically. In two experiments, we show that the time taken to plan a referring expression—as reflected by speech onset latencies—is influenced by distractor set size and by the number of properties required, but this crucially depends on the discriminability of the properties under consideration. We discuss the implications for current models of reference production and recent work on the role of salience in visual search. (shrink)

Decision making in any brain is imperfect and costly in terms of time and energy. Operating under such constraints, an organism could be in a position to improve performance if an opportunity arose to exploit informative patterns in the environment being searched. Such an improvement of performance could entail both faster and more accurate (i.e., reward-maximizing) decisions. The present study investigated the extent to which human participants could learn to take advantage of immediate patterns in the spatial arrangement of serially (...) presented foods such that a region of space would consistently be associated with greater subjective value. Eye movements leading up to choices demonstrated rapidly induced biases in the selective allocation of visual fixation and attention that were accompanied by both faster and more accurate choices of desired goods as implicit learning occurred. However, for the control condition with its spatially balanced reward environment, these subjects exhibited preexisting lateralized biases for eye and hand movements (i.e., leftward and rightward, respectively) that could act in opposition not only to each other but also to the orienting biases elicited by the experimental manipulation, producing an asymmetry between the left and right hemifields with respect to performance. Potentially owing at least in part to learned cultural conventions (e.g., reading from left to right), the findings herein particularly revealed an intrinsic leftward bias underlying initial saccades in the midst of more immediate feedback-directed processes for which spatial biases can be learned flexibly to optimize oculomotor and manual control in value-based decision making. The present study thus replicates general findings of learned attentional biases in a novel context with inherently rewarding stimuli and goes on to further elucidate the interactions between endogenous and exogenous biases. (shrink)

Observers can learn the locations where salient distractors appear frequently to reduce potential interference. The effect that observers appear to learn the spatial distribution of salient but task-irrelevant distractors in the visual environment to reduce the interference caused by such distractors was referred to as ‘statistical learning of distractor locations’. Emerging studies agreed that the observed reduction of distractor interference is largely attributable to better suppression of distractor in frequent locations, however, concerning how this spatial distractor suppression is implemented within (...) the functional architecture of search guidance, and how the learned suppression is processed in the brain to reduce the interference, remains debated and poorly understood. The line of studies of the current dissertation, therefore, explores the cognitive and neural mechanism underlying spatial distractor suppression based on statistical learning. Using psychophysical experiments, the first two studies examined a series of potentially ‘confounding’ factors that might lead to different theoretical conclusions concerning the locus of learned spatial distractor suppression in different studies. We found that irrespective of whether a salient singleton distractor is more likely to occur at multiple locations within a subregion of the display or at a specific location, observers are both likely to adopt the priority-map-based suppression strategy and dimension-based suppression strategy to reduce interference of distractor in the frequent region. Notably, a critical factor determining which strategy is adopted is whether the distractor and non-distractor items swap colors randomly across trials: without color swapping, observers are more likely to acquire a dimension-based suppression; with color swapping, they prefer to develop a priority-map-based suppression in the first beginning, and potentially shift to dimension-based suppression later with the course of learning. The third study employed functional magnetic resonance imaging techniques with the distractor-location learning paradigm with two types of distractors defined in either the same- or different- visual dimension relative to the target. We disclosed that statistical learning of distractor locations involves suppression down to the level of the early visual cortex to reduce distractor interference, potential different neural mechanisms of spatial distractor suppression between distractors defined in a different and the same dimension to the target. With different-dimension distractors, higher-level, dimension-specific filtering mechanisms plays a role to reduce the interference; with same-dimension distractors, interference reduction relies on cutting down lower-level sensory signals. (shrink)

We analysed location priming effects, and thus the ability to integrate visual information across subsequent trials in the three studies presented in the following chapters. Based on previous findings in healthy subjects priming effects occur under conditions that require no attentional shifts in-between subsequent trials, i.e. with the subject’s fixation maintained and the search displays presented at retinotopically equal locations with respect to the fixation cross. In study 1 we tested whether location-based priming effects would outlive spatial shifts of attention (...) in healthy subjects. The basic assumption, derived from Pisella and Mattingley´s account was they would, and that the outliving would be based on intact spatial remapping mechanisms operating in healthy subjects along with attention shifts. The aim of study 1 in view of further investigations in patients, i.e. in studies 2 and 3 was to test the suitability of the priming paradigm to serve our purpose to investigate spatial remapping abilities, and furthermore, in patients, purported deficits. To test whether priming effects would outlive saccadic shifts of overt attention, subjects had to re-fixate the fixation cross in turns on the left and on the right side of the monitor between subsequent trials. In two separate experiments priming effects were measured at post-saccadically retinotopic and spatiotopic locations, respectively, and compared to effects in a control experiment requiring no attention shifts. The experiments were also applied in study 2. To test whether priming effects would outlive covert shifts of attention subjects´ attention was distracted between subsequent trials while their fixation was maintained. In two separate experiments priming effects were measured after exogenous and endogenous distraction, respectively, and compared to a control experiment without distraction. The experiments were also applied in study 3. The presence of priming effects despite interfering attention shifts could be taken as evidence that processes that integrate visual information along with attention shifts, i.e. spatial remapping mechanisms, operate flawlessly in healthy subjects. The aim of study 2 was to test whether the parietal cortex provides the neural correlate of spatial remapping as assumed by Pisella and Mattingley. To that end, we tested whether spatial remapping deficits would occur after saccadic shifts of overt attention in patients with right parietal lesions. Deficits were expected to be indicated by altered or disturbed priming effects in those patients as compared to priming effects in healthy control subjects and furthermore, in patients with right-hemispheric lesions not involving the parietal lobe. Latter patients were tested, to control for and differentiate between deficits occurring more generally after right-hemispheric damages and specific deficits occurring after right parietal damages. Moreover, given the crucial role of priming for visual search disturbed priming as an indicator of deficient spatial remapping would provide support for the assumption made by Pisella and Mattingley that spatial remapping deficits contribute to visual search impairments as they are often observed in patients with right parietal lesions. The aim of study 3 was to test the model’s assumption that spatial remapping is required after spatial shifts of covert attention. Again, we compared priming effects of patients with right parietal lesions to those of patients with right-hemispheric lesions without parietal involvement, and healthy subjects. We expected priming effects to be disturbed in patients with right parietal lesions provided that covert attention shifts induce spatial remapping requirements, and that the anatomical site of spatial remapping mechanisms operating to integrate visual information across spatial shifts of covert attention is located in the parietal lobe. (shrink)