VISUALCROWDING

Visual crowding: The paradox of position

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 Obiettivo del progetto (Objective)

'Visual crowding is the disruptive effect of “clutter” on our ability to recognise objects, despite their being identifiable in isolation. This effect is particularly strong in our peripheral vision, making crowding the fundamental limit on over 95% of the visual field. Understanding crowding will thus reveal much about how we recognise objects, as well as how to present information to those who rely on peripheral vision (e.g. macular degeneration) and those with elevated crowding (e.g. amblyopia).

The dominant view of crowding is as an excessive integration of object features that simplifies the crowded region into efficiently processed texture. A key assumption here is that the position of objects is lost – otherwise, the true features would be seen in their true locations. This is, however, inconsistent with the high positional specificity of crowding: its magnitude relies strongly on the position of objects, both in relation to one another (more crowding for adjacent objects) and across the visual field (more crowding peripherally). In addition, while crowding affects object identities, it rarely fills the spaces in between. Simple feature integration would not retain this specificity. We call this discrepancy between gross object position and the position of their features “the paradox of position” in crowding.

Our psychophysical experiments and computational modeling will examine this hitherto unexplored aspect of crowding in two key ways. The first will delineate the circumstances where position encoding is reliable and where it breaks down. The second will examine the rules that govern “what goes where” by manipulating aspects of the stimuli likely to influence this process (e.g. spatial frequency and border ownership). The outcome will be an insight into both the mechanisms of crowding, a key process in vision, and the way that object identities are tied to positions, a key issue of the ‘binding problem’ in object recognition more generally.'

Introduzione (Teaser)

Objects are harder to see in the periphery than when they are viewed directly. An EU-funded study investigated visual crowding, the phenomenon responsible for this.

Descrizione progetto (Article)

Visual crowding refers to how the brain perceives objects in the periphery. It occurs when the objects in the dominant view render those in the periphery as jumbled and blurred together, making them unrecognisable.

The discrepancy in visual crowding is that people can generally tell the position of the objects themselves, but often cannot differentiate the positions of the features within the object. This is called the paradox of position. The project 'Visual crowding: The paradox of position' (VISUALCROWDING) conducted experiments to better understand this paradox and the phenomenon of visual crowding.

In the first part of the study, researchers found that visual crowding occurs much more frequently when the positions of the objects themselves are unknown, supporting the idea that uncertainty about location and feature location leads to visual crowding. Researchers then explored what would happen if one feature became defined in the peripheral field. They found that understanding the location and features of just one object releases the crowding entirely.

Researchers then investigated the neural mechanisms behind crowding. Using functional magnetic brain resonance imaging studies, they found that crowding changes even the earliest stages of brain processing, with an increasing effect higher up the cortical hierarchy. This finding indicates that crowding has widespread effects throughout the visual system.

Study results provided new insights into the phenomenon of crowding. This phenomenon can be viewed as a higher-level form of position uncertainty within the visual system that is nonetheless heavily dependent upon earlier stages of processing.

These findings have the potential to guide future research in the field. They also may help direct treatment for strabismic amblyopia ('lazy eye') and dyslexia, where crowding is elevated and interferes with perception.