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Title: Is visual crowding a multi-level phenomenon?
Author: Reuther, Josephine
ISNI:       0000 0004 6498 1805
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2017
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Visual crowding is a dramatic breakdown of object recognition that has been studied extensively as a gateway to determine the mechanisms that underlie normal object recognition. Despite numerous proposed models and mechanisms, a unifying account has yet to be found. Proposed mechanisms reach from purely hierarchical, bottom-up accounts that place crowding early in the processing stream, to high-level attention-based accounts that allow for recurrent processing and top-down feed-back. The aim of the current work was to investigate a range of factors that would help to differentiate between these accounts. Firstly, object-category was studied as a factor that would be expected to modulate crowding if the phenomenon were to affect object recognition during several stages along the processing stream. Secondly, knowledge was studied as a possible source of top-down feedback that, if found to have a direct influence on crowding, would provide evidence against a purely hierarchical account for object recognition. Thirdly, anticipation of flanker-presence was studied as a factor modulating volitional attention-allocation. Observing an influence of anticipation on object recognition under the influence of crowding, would provide support that crowding may be the result of a limitation to focus attention. Finally, object-familiarity was studied as another factor that may modulate crowding via top-down feedback. Of these factors, only object-familiarity was found to have an influence on visual crowding. However, instead of being the result of top-down feedback, hard-wired pathways developed based on repeated exposure might explain the effect of object-familiarity. In summary, none of the studied factors provided univocal evidence to suggest that crowding were to occur at multiple levels of object recognition, or that crowding were to be influenced by higher-level effects. Hence, it may be concluded that a purely hierarchical bottom-up account is sufficient to account for the effects visual crowding exerts on normal object recognition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Visual perception