Subjective appearance and objective discrimination of shapes in the periphery of the visual field

This thesis focuses on three different yet related phenomena, in the framework of the interplay between foveal and peripheral vision. Three exceptions to traditional visual models are discussed, illustrating three scenarios: 1) foveal vision aids peripheral discrimination, 2) foveal vision does not interact with peripheral vision, and 3) foveal vision hinders peripheral discrimination. This thesis also explores the difference between subjective and objective precepts, illustrating the presence of dissociations between the two. Part I reviews literature on the visual system and models of visual perception. Part II discusses Foveal Feedback, a mechanism where foveal retinotopic cortex recruitment enhances peripheral discrimination. Foveal Feedback challenges the traditional retinotopic model of visual perception. In this part, different aspects of Foveal Feedback are investigated: 1) first, a more precise estimate of the timing of the feedback; second, the existence of this mechanism for different types of stimuli and tasks, along with its modulation by task and stimuli complexity; 3) third, a possible relation with visual imagery. Part III presents a study on the Honeycomb Illusion, a particular stimulus where mechanisms usually employed when looking at pattern (uniformity assumption, extrapolation) do not occur. The Honeycomb Illusion represents a situation in which there is no interaction between foveal and peripheral vision, thus being an exception to the traditional view of peripheral information inferred from foveal vision. Part IV introduces the Central Region Interference with Periphery (CRIP) effect, illustrating how central vision can hinder peripheral discrimination, and challenging predictive processing models. Through two different studies, it is demonstrated that we do not always rely on central vision to disambiguate elements in the periphery. The final section summarises findings, addresses open questions, and suggests future research directions.