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You are watching: Peripheral vision better than central vision

The limits of visual resolution as a function of retinal eccentricity, with the visual field divided into three regions: Foveal, Parafoveal, and Peripheral. Resolution limits are in terms of spatial frequency cut-offs in cycles/degree (cpd), based on the results of Loschky et al. (2005).
The limits of visual resolution as a function of retinal eccentricity, with the visual field divided into three regions: Foveal, Parafoveal, and Peripheral. Resolution limits are in terms of spatial frequency cut-offs in cycles/degree (cpd), based on the results of Loschky et al. (2005).
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A key question that has received little attention is what is the relative importance for recognizing scene gist of central vision (foveal and parafoveal), versus peripheral vision? What is the relative efficiency of gist information from central versus peripheral vision? Finally, how well is gist recognition performance predicted by mathematically defined relationships between retinal eccentricity and vision, such as cortical magnification functions (described below)? 
A great deal is known about the neurobiology of central versus peripheral vision, and we will only briefly touch on a few highly salient points of contrast here (for an excellent review, see Wilson, Levi, Maffei, Rovamo, & DeValois, 1990). The drop-off in visual resolution with retinal eccentricity, shown in Figure 1, can be explained in several ways. First, the density of retinal receptors, particularly cones, is far greater in foveal and parafoveal vision than in the visual periphery, allowing central vision to encode higher spatial frequencies. Then, the pooling of information from retinal receptors by retinal ganglion cells is far greater in the visual periphery than in foveal or parafoveal vision, leading to a loss of visual resolution (i.e., higher spatial frequencies) in the periphery. Consequently, both the lateral geniculate nucleus (LGN) and the primary visual cortex (V1) devote many more cells to processing central vision than to peripheral vision, a fact known as cortical magnification. Because of this, small detailed pattern information, encoded by higher spatial frequencies, can be processed in central vision, whereas the same pattern information must be enlarged, and encoded by lower spatial frequencies, to be resolved in the visual periphery (Virsu, Näsänen, & Osmoviita, 1987; Virsu & Rovamo, 1979). It is for this reason that people foveate (or fixate) objects in scenes in order to recognize them. Studies have shown that perception of an object is best when viewers fixate within 1–2° of it, with performance dropping off rapidly with increasing distance from the closest fixation to the object (Henderson & Hollingworth, 1999; Hollingworth et al., 2001; Nelson & Loftus, 1980; O"Regan, Deubel, Clark, & Rensink, 2000; Pringle, 2000).3 If gist recognition requires the use of detailed information (specifically, spatial frequencies > 10 cpd), then central information will be important, since high spatial frequencies are only processed centrally (as seen in Figure 1). Interestingly, a study by Oliva and Schyns (1997) showed that higher spatial frequency information can be highly useful for scene gist recognition when it provides diagnostic information, suggesting a possible key role for central vision in scene gist recognition. 
Nevertheless, the issue of which spatial frequency band, or spatial scale, of scene information is most useful for scene gist recognition suggests a reason to argue for the importance of peripheral vision for gist. Figure 1 shows that to the extent that lower spatial frequencies (≤10 cpd) are important for scene gist recognition, peripheral vision will be important, because it can provide them. Several studies bear on this issue. Schyns and Oliva (1994) showed a bias for viewers to recognize scenes encoded by lower spatial frequencies early in processing, with recognition based on higher frequencies occurring only later in processing.4 Using very different methods, McCotter, Gosselin, Sowden, and Schyns (2005) showed that the information most important for recognizing scene gist (specifically, structure encoded in the phase spectrum) was contained in the lower spatial frequencies. Similarly, studies of scene gist masking have shown that visual masks containing predominantly lower spatial frequencies are the most effective at disrupting scene gist recognition (Harvey, Roberts, & Gervais, 1983; Loschky et al., 2007). Furthermore, the fact that people can recognize the gist of scenes containing only lower spatial frequency information, yet cannot recognize individual objects in those scenes, has been used to argue that object recognition may not be needed for scene gist recognition (Schyns & Oliva, 1994), and instead the global layout of the scene may be more important (Sanocki, 2003; Sanocki & Epstein, 1997). The above suggests that peripheral vision may be important for recognizing scene gist, since it can resolve the lower spatial frequencies so useful for gist. However, one could go further and argue that peripheral vision might be better at recognizing scene gist than central vision because the periphery contains a larger expanse of the visual field from which to gather such information. 


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A number of studies have investigated the roles of central versus peripheral vision in scene perception using what are known as the “Window” and “Scotoma” paradigms (for review, see van Diepen, Wampers, & d"Ydewalle, 1998). Examples of each are shown in Figure 2. The Window paradigm gets its name by analogy to viewing a scene through a Window, for example a porthole. Unaltered imagery is presented within the Window, which is centered on the viewers" fovea, while outside the Window, imagery is either absent (Saida & Ikeda, 1979) or degraded by adding noise, image filtering, or other means (Kortum & Geisler, 1996; Loschky & McConkie, 2002; Parkhurst, Culurciello, & Neiburm, 2000; Shioiri & Ikeda, 1989; van Diepen & Wampers, 1998). The Scotoma is an inverted Window, where central information is blocked from view, while information outside the Scotoma is unaltered (Henderson, McClure, Pierce, & Schrock, 1997; van Diepen, Ruelens, & d"Ydewalle, 1999). This term is taken from an analogous medical condition where a specific region of the visual field is degraded or blocked from view. Window and Scotoma paradigms were first used to study reading processes (McConkie & Rayner, 1975; Rayner & Bertera, 1979), and have been later used to study scene perception (Geisler & Perry, 1999; Henderson et al., 1997; Loschky & McConkie, 2002; Loschky, McConkie, Yang, & Miller, 2005; Parkhurst et al., 2000; Parkhurst & Niebur, 2002; Reingold, Loschky, McConkie, & Stampe, 2003; Shioiri & Ikeda, 1989; van Diepen & Wampers, 1998; van Diepen et al., 1998). They allow one to use real-world scenes in meaningful tasks, while varying which regions of the visual field provide information. The logic of both paradigms is that processing will be disrupted to the extent that the missing information is needed for the task, whereas processing will be normal to the extent that the missing information is not needed.