Peripheral vision

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Peripheral vision is a part of vision that occurs outside the very center of gaze. There is a broad set of non-central points in the field of view that is included in the notion of peripheral vision. "Far peripheral" vision exists at the edges of the field of view, "mid-peripheral" vision exists in the middle of the field of view, and "near-peripheral", sometimes referred to as "para-central" vision, exists adjacent to the center of gaze.

Peripheral vision is weaker in humans, compared with other animals, especially at distinguishing color and shape. This is because receptor cells on the retina are greater at the center and lowest at the edges (see visual system for an explanation of these concepts). In addition, there are two types of receptor cells, rod cells and cone cells; rod cells are unable to distinguish color and are predominant at the periphery, while cone cells are concentrated mostly in the center of the retina, the fovea.

Flicker fusion threshold is higher for peripheral than foveal vision. Peripheral vision is good at detecting motion (a feature of rod cells), peripheral vision is a load of rubbish

Spatial hearing

Spatial hearing experiments conducted on humans have been used by researchers working in areas spanning medicine, humanbiology, and psychology. Overviews of perception experiments and resulting theories of human sound localization are presented by Blauert [94] and Yost and Dye [95]. The fundamental principles behind sound localization behavior research involve the relationship between the physics of a sound arriving at the eardrum and the geometry of the head. The shape of the head, the spacing between the ears, and the structure of the pinna create a spectral transformation of incoming sounds that depends on the direction of origin.

And is relatively weak at night or in the dark, when the lack of color cues and lighting makes cone cells far more useful. This makes it useful for avoiding predators, who tend to hunt at night and may attack unexpectedly.

Ovals A, B and C show which portions of the chess situation a chess master can reproduce correctly with his peripheral vision. Lines show path of foveal fixation during 5 seconds when the task is to memorize the situation as correctly as possible. Image from based on data by

Peripheral vision loss results in tunnel vision.

The distinctions between foveal(sometimes also called central) and peripheral vision are reflected in subtle physiological and anatomical differences in the visual cortex. Different visual areas contribute to the processing of visual information coming from different parts of the visual field, and a complex of visual areas located along the banks of the interhemispheric fissure (a deep groove that separates the two brain hemispheres) has been linked to peripheral vision. It has been suggested that these areas are important for fast reactions to visual stimuli in the periphery, and monitoring body position relative to gravity. It is used to see dangers coming up besides you.

Peripheral vision can be practiced, jugglers that regularly locate and catch objects in their peripheral vision do have improved abilities. Jugglers do not follow the paths of individual objects with their eyes, instead they focus on a defined point in mid-air, so almost all of the information necessary for successful catches is perceived in the near-peripheral region. Some juggling patterns and disciplines require extraordinary peripheral vision.

Being fully aware of your peripheral vision allows you to focus on your entire field of vision instead of focusing on just one spot. This should enable you to notice small movements at the edge of your sight and so be more aware of your surroundings and ready to react to things other than those directly in front of you. The opening move from the Karate form 'Kushan Ku' includes a move used to quickly engage peripheral vision. Standing with your hands hanging down in front, palms facing inward (one hand on top of the other), you then raise them directly in front of yourself so that you are pointing at the sky and they are at the top of your field of vision. While still looking forward, but concentrating on seeing your hands, you then bring them down by either side, slowly drawing a large circle and ending up in the starting position but with your palms facing outward. As they come down you should follow them without moving your gaze and so becoming fully aware of the area inside the circle.

Functions

The main functions of peripheral vision are:

• recognition of well-known structures and forms with no need to focus by the foveal line of sight.
• identification of similar forms and movements (Gestalt psychology laws)
• delivery of sensations which form the background of detailed visual perception.

See also

• Averted vision
• Perimetry
• Visual field
• Vision span
• Visual perception
• Fovea
• Eye movement
• Eye movement in music reading