The Fovea-Periphery Dichotomy: Understanding Visual Acuity and Peripheral Perception in Human Vision
Lucio Cavallari, November 2023
The fovea, located in the center of the retina, contains a high density of cone cells responsible for detailed vision and colour perception(Otten et al., 2017)1. As a result, hyperacuity thresholds (the ability to discern fine details) increase more rapidly with eccentricity (distance from the center of vision) than visual resolution thresholds. In contrast, the periphery of the retina has fewer cone cells, leading to lower visual acuity but a wider field of view (Anderson, Mullen, & Hess, 19912; Westheimer, 19823). Despite the lower acuity, peripheral vision has unique characteristics, including sensitivity to motion, detection of large and global patterns, and a heightened ability to perceive the gist or overall scene information (Anderson, Mullen and Hess, 1991). As we move towards the periphery of our visual field, our ability to perceive colour (chromatic acuity) diminishes more rapidly than our ability to perceive brightness (luminance acuity)(Anderson, Mullen and Hess, 1991). This decline is attributed to factors occurring after the initial reception of light by the photoreceptors (J, T and F, 19914; Westheimer, 1982).
These differences arise from the evolutionary trade-off between the need for detailed information (fovea) and the need for broad situational awareness (periphery). The periphery excels at detecting potential threats, monitoring the environment, and providing a rapid overview of the surroundings, contributing to the rich phenomenology observed (Li et al., 20215).
Gist processing, known for rapidly extracting the primary meaning from visual information, proves effective for various tasks. Both brain imaging and behavioral studies highlight a tendency to amalgamate information in peripheral vision, suggesting an interplay between sensory (bottom-up) and contextual (top-down) processing (Li et al., 2021).
Drawing insights from Li et al.’s (2021) study on Numerosity Perception in Peripheral Vision, where research emphasises that what is perceived in the periphery significantly shapes judgments regarding the quantity of objects in the central area of focus, we find that the impact of peripheral visual information is not uniform across tasks. While the peripheral spatial context consistently holds importance, the degree of its influence varies depending on the specific nature of the task being undertaken (Li et al., 2021).
This variability in the impact of peripheral vision becomes particularly apparent in studies such as Otten et al.’s (2017), which explore the brain’s role in visual perception. The brain, in response to the less accurate or detailed visual data from the periphery, engages in a process of filling in or modifying the perceived peripheral visual information. This process known as “The Uniformity Illusion” aims to create a more coherent and uniform visual experience.
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uniformity illusion: Central stimuli can determine peripheral
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https://doi.org/10.1177/0956797616672270. ↩︎ - Anderson, S.J., Mullen, K.T. and Hess, R.F. (1991). Human
peripheral spatial resolution for achromatic and chromatic
stimuli: limits imposed by optical and retinal factors. The Journal
of Physiology, 442(1), pp.47–64. doi:https://doi.org/10.1113/
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pp.47–64. ↩︎ - Li, M.S., Abbatecola, C., Petro, L.S. and Muckli, L. (2021).
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