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"Form perception."
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The uncrowded window of object recognition
This perspective article proposes a general law (Bouma law), which states that a visual object is crowded (and therefore cannot be perceived) when spacing between multiple objects is less than a critical spacing value. Crucially, this value is independent of the object.
It is now emerging that vision is usually limited by object spacing rather than size. The visual system recognizes an object by detecting and then combining its features. 'Crowding' occurs when objects are too close together and features from several objects are combined into a jumbled percept. Here, we review the explosion of studies on crowding—in grating discrimination, letter and face recognition, visual search, selective attention, and reading—and find a universal principle, the Bouma law. The critical spacing required to prevent crowding is equal for all objects, although the effect is weaker between dissimilar objects. Furthermore, critical spacing at the cortex is independent of object position, and critical spacing at the visual field is proportional to object distance from fixation. The region where object spacing exceeds critical spacing is the 'uncrowded window'. Observers cannot recognize objects outside of this window and its size limits the speed of reading and search.
Journal Article
Computational origins of shape perception
Shape perception is central to human vision, but its developmental origins remain unknown. Here we show that shape perception develops from three ingredients: (1) generic fitting systems, (2) embodied visual experiences, and (3) biologically plausible sensors. We first show that generic fitting models (transformers) trained on embodied visual experiences change from color-based to shape-based visual systems. We then perform in silico controlled-rearing experiments to determine what causes this developmental change. We find that view diversity—experiencing many views of the same object—produces shape perception. For embodied agents, view diversity comes for free: by moving through the world, agents acquire diverse temporally linked views, explaining how and why animals develop shape perception so rapidly. But when view diversity is restricted, by limiting where an agent can look or move, shape perception fails to develop. Finally, we show that retinas naturally transform images in ways that enhance shape learning, providing a biologically plausible substitute for artificial image augmentations. Together, our results support generic fitting theories of brain development and provide a template for building human-like shape perception in machines.
Journal Article
The relative contribution of color and material in object selection
Object perception is inherently multidimensional: information about color, material, texture and shape all guide how we interact with objects. We developed a paradigm that quantifies how two object properties (color and material) combine in object selection. On each experimental trial, observers viewed three blob-shaped objects-the target and two tests-and selected the test that was more similar to the target. Across trials, the target object was fixed, while the tests varied in color (across 7 levels) and material (also 7 levels, yielding 49 possible stimuli). We used an adaptive trial selection procedure (Quest+) to present, on each trial, the stimulus test pair that is most informative of underlying processes that drive selection. We present a novel computational model that allows us to describe observers' selection data in terms of (1) the underlying perceptual stimulus representation and (2) a color-material weight, which quantifies the relative importance of color vs. material in selection. We document large individual differences in the color-material weight across the 12 observers we tested. Furthermore, our analyses reveal limits on how precisely selection data simultaneously constrain perceptual representations and the color-material weight. These limits should guide future efforts towards understanding the multidimensional nature of object perception.
Journal Article
Forms : whole, rhythm, hierarchy, network
\"Forms offers a powerful new answer to one of the most pressing problems facing literary, critical, and cultural studies today--how to connect form to political, social, and historical context. Caroline Levine argues that forms organize not only works of art but also political life--and our attempts to know both art and politics. Inescapable and frequently troubling, forms shape every aspect of our experience. But forms don't impose their order in any simple way. Multiple shapes, patterns, and arrangements, overlapping and colliding, generate complex and unpredictable social landscapes that challenge and unsettle conventional analytic models in literary and cultural studies. Borrowing the concept of \"affordances\" from design theory, this book investigates the specific ways that four major forms--wholes, rhythms, hierarchies, and networks--have structured culture, politics, and scholarly knowledge across periods, and it proposes exciting new ways of linking formalism to historicism and literature to politics. Levine rereads both formalist and antiformalist theorists, including Cleanth Brooks, Michel Foucault, Jacques Rancière, Mary Poovey, and Judith Butler, and she offers engaging accounts of a wide range of objects, from medieval convents and modern theme parks to Sophocles's Antigone and the television series The Wire. The result is a radically new way of thinking about form for the next generation and essential reading for scholars and students across the humanities who must wrestle with the problem of form and context\"-- Provided by publisher.
Book
Symmetry Detection in Autistic Adults Benefits from Local Processing in a Contour Integration Task
Symmetry studies in autism are inconclusive possibly due to different types of stimuli used which depend on either local or global cues. Therefore, this study compared symmetry detection between 20 autistic and 18 non-autistic adults matched on age, IQ, gender and handedness, using contour integration tasks containing open and closed contours that rely more on local or global processing respectively. Results showed that the autistic group performed equally well with both stimuli and outperformed the non-autistic group only for the open contours, possibly due to a different strategy used in detecting symmetry. However, there were no group differences for the closed contour. Results explain discrepant findings in previous symmetry studies suggesting that symmetry tasks that favour a local strategy may be advantageous for autistic individuals. Implications of the findings towards understanding visual sensory issues in this group are discussed.
Journal Article
Effects of nicotine on response inhibition and interference control
Nicotine is a cholinergic agonist with known pro-cognitive effects in the domains of alerting and orienting attention. However, its effects on attentional top-down functions such as response inhibition and interference control are less well characterised. Here, we investigated the effects of 7 mg transdermal nicotine on performance on a battery of response inhibition and interference control tasks. A sample of
N
= 44 healthy adult non-smokers performed antisaccade, stop signal, Stroop, go/no-go, flanker, shape matching and Simon tasks, as well as the attentional network test (ANT) and a continuous performance task (CPT). Nicotine was administered in a within-subjects, double-blind, placebo-controlled design, with order of drug administration counterbalanced. Relative to placebo, nicotine led to significantly shorter reaction times on a prosaccade task and on CPT hits but did not significantly improve inhibitory or interference control performance on any task. Instead, nicotine had a negative influence in increasing the interference effect on the Simon task. Nicotine did not alter inter-individual associations between reaction times on congruent trials and error rates on incongruent trials on any task. Finally, there were effects involving order of drug administration, suggesting practice effects but also beneficial nicotine effects when the compound was administered first. Overall, our findings support previous studies showing positive effects of nicotine on basic attentional functions but do not provide direct evidence for an improvement of top-down cognitive control through acute administration of nicotine at this dose in healthy non-smokers.
Journal Article