The article presents an analytical review of studies in the field of extrafoveal perception. The region of extrafoveal vision combines the parafovea and periphery of the retina, so extrafoveal perception is the perception of objects which projections are outside of the fovea. For a long time, it has been believed that extrafoveal vision, in contrast to foveal, has a lower acuity and resolution and is used mainly for preliminary analysis of the visual field and selection of relevant objects for their more thorough analysis in fovea. However, the literature shows that extrafoveal perception is much more interesting and autonomous process as it has been previously considered. The paper analyzes a number of works showing that it is possible to identify both specific features of simple stimuli and rather complex objects, such as faces or whole scenes, up to the possibility of their semantic analysis, even in extrafoveal vision. The review considers the history of studies on extrafoveal perception, from the earliest works (Hueck, 1840; Aubert, Foerster, 1857) to the most recent ones of the last 5 years. These works have analyzed the main factors influencing the effectiveness of extrafoveal vision, for example, cortical magnification factor, which reflects differences in the number of neurons in the visual cortex responsible for processing stimuli depending on the region of the retina: the closer the object is to the fovea, the more neurons are involved in its processing, and vice versa. Other factors determining the efficacy of extrafoveal perception include the following: crowding effect when the target object on the periphery surrounded by distractors is identified worse than a separately located stimulus; specific characteristics of a target and distractors (for example, contexts evoking pop-out effect). Crowding effect is also related to the question of correlating two forms of processing extrafoveal information: preattentive processing (parallel “bottom up” processing) and covert attention (moving the point of deeper analysis along the visual field without eye movements) which can be controlled up to some degree. The other factors influencing the effectiveness of extrafoveal perception concern the context of a task (categorical search in laboratory conditions, analysis of the real world scenes, reactions to extrafoveal stimuli during definite activity) and individual differences. Additionally, we have analyzed the works on the possibilities of training extrafoveal perception, which can affect both higher-level processes, for example, identification of the context of complex scenes, perception of emotions and categorical visual search, and lower-level visual functions, such as identification of spatial orientation, contrast perception and reduction of crowding effect.
Left-right and upper-lower light sensitivity asymmetry in visual field defects caused by pituitary adenoma: a retrospective observational study
