An Accurate Method for Determining the Conspicuity Area Associated With Visual Targets

Pretorius, L.L.; Hanekom, Johan J.

doi:10.1518/001872006779166370

Cited by 10 publications

(8 citation statements)

References 30 publications

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“…Our finding that both the HVA and VMA emerge gradually as we move from the HM to the VM further challenges the idea that there is a constant upper versus lower visual field asymmetry. For instance, changes in performance across isoeccentric locations have been described simply as an ellipse (e.g., Anderson, Cameron & Levine, 2014;Engel, 1971;Pretorius & Hanekom, 2006). Although the horizontal elongation of the elliptical performance field can capture the strong HVA we found in SF sensitivity, an elliptical model cannot capture the robust VMA between upper and lower visual fields observed in the present study, as well as in other studies (e.g., Abrams et al, 2012;Cameron et al, 2002;Corbett & Carrasco, 2011;Fuller et al, 2008;Montaser-Kouhsari & Carrasco, 2009).…”

Section: Discussioncontrasting

confidence: 60%

Asymmetries in visual acuity around the visual field

Barbot¹,

Xue²,

Carrasco³

2020

Preprint

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Human vision is heterogeneous across the visual field. At a fixed eccentricity, performance is better along the horizontal than the vertical meridian, and better along the lower than the upper vertical meridian. These asymmetric patterns, termed performance fields, have been found in numerous visual tasks, including those mediated by contrast sensitivity and spatial resolution. However, it is unknown whether spatial resolution asymmetries are confined to the cardinal meridia or whether, and how far, they extend into the upper and lower hemifields. Here, we measured the extent of the vertical meridian asymmetry by assessing spatial frequency (SF) sensitivity at isoeccentric peripheral locations (10 degree eccentricity), every 15º of polar angle. On each trial, observers judged the orientation (±45º) of a suprathreshold grating stimulus varying in spatial frequency. We estimated 75%-correct SF thresholds, SF cutoff points (i.e., chance-level) and slopes of the psychometric function for each of the 24 isoeccentric locations. We found higher SF sensitivity in the lower than the upper hemifield, with this asymmetry being most pronounced at the vertical meridian and decreasing gradually as the angular distance from the vertical meridian increased. This gradual change in SF sensitivity with polar angle reflected a shift of the psychometric function without reliable changes in slope. The same pattern was found under binocular and monocular conditions. These findings advance our understanding of visual processing around the visual field and help constrain models of visual perception.

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Section: Discussioncontrasting

confidence: 60%

Asymmetries in visual acuity around the visual field

Barbot¹,

Xue²,

Carrasco³

2020

Preprint

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“…Previous measurements of the conspicuity area (e.g., Engel, 1971; Pretorius & Hanekom, 2007) have suggested that the visual performance field is simply an ellipse. The HVA derived from the present data illustrates the horizontal elongation of the elliptical performance field; however, an elliptical model cannot capture the robust VMA.…”

Section: Discussionmentioning

confidence: 95%

“…The shape of the visual performance field, with eccentricity held constant, is characterized by a Horizontal–Vertical Anisotropy (HVA), in which performance is better in the East 1 and West relative to the North and South, and a vertical meridian asymmetry (VMA), in which performance is better in the South than in the North. These performance fields emerge in contrast sensitivity and spatial resolution tasks (Altpeter, Mackeben, & Trauzettel-Klosinski, 2000; Anderson, Wilkinson, & Thibos, 1992; Cameron, Tai, & Carrasco, 2002; Carrasco, Talgar, & Cameron, 2001; Carrasco, Williams, & Yeshurun, 2002; Low, 1943a, 1943b; Lundh, Lennerstrand, & Derefeldt, 1983; Mackeben, 1999; Millodot & Lamont, 1974; Montaser-Kouhsari & Carrasco, 2009; Pointer & Hess, 1989; Pointer & Hess, 1990; Regan & Beverley, 1983; Rijsdijk, Kroon, & van der Wildt, 1980; Robson & Graham, 1981; Rovamo et al, 1982; Seiple et al, 2004; Silva et al, 2008; Silva et al, 2010; Skrandies, 1985; Talgar & Carrasco, 2002), as well as in visual search tasks (Carrasco, Giordano, & McElree, 2004; Chaikin, Corbin, & Volkmann, 1962; Kristjánsson & Sigurdardottir, 2008; Kröse & Julesz, 1989; Najemnik & Geisler, 2008, 2009; Pretorius & Hanekom, 2007; Rezec & Dobkins, 2004). Both the HVA and the VMA also exist in the rate of information accrual at isoeccentric locations: information accrual is faster along the horizontal than the vertical meridian, and it is faster along the lower than the upper vertical meridian (Carrasco, Giordano, & McElree, 2004).…”

Section: Introductionmentioning

confidence: 99%

Isoeccentric locations are not equivalent: The extent of the vertical meridian asymmetry

Abrams¹,

Nizam²,

Carrasco³

2012

Vision Research

151

181

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Performance in visual tasks is limited by the low-level mechanisms that sample the visual field. It is well documented that contrast sensitivity and spatial resolution decrease as a function of eccentricity and that those factors impair performance in “higher level” tasks, such as visual search. Performance also varies consistently at isoeccentric locations in the visual field. Specifically, at a fixed eccentricity, performance is better along the horizontal meridian than the vertical meridian, and along the lower than the upper vertical meridian. Whether these asymmetries in visual performance fields are confined to the vertical meridian or extend across the whole upper versus lower visual hemifield has been a matter of debate. Here, we measure the extent of the upper versus lower asymmetry. Results reveal that this asymmetry is most pronounced at the vertical meridian and that it decreases gradually as the angular distance (polar angle) from the vertical meridian increases, with eccentricity held constant. Beyond 30° of polar angle from the vertical meridian, the upper to lower asymmetry is no longer reliable. Thus, the vertical meridian is uniquely asymmetric and uniquely insensitive. This pattern of results is consistent with early anatomical properties of the visual system and reflects constraints that are critical to our understanding of visual information processing.

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“…The two effects have been described by Carrasco and colleagues and called the "horizontal-vertical anisotropy" and the "vertical meridian asymmetry" [2,[4][5][6][7][8]. Such effects, often called performance fields, are found in numerous tasks, including contrast sensitivity and spatial resolution [5,6,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] (Fig 1), visual search [24][25][26][27][28][29][30][31], crowding [32][33][34], motion perception [35], visual short-term memory [36], contrast appearance [7] and spatial frequency appearance [37]. These effects can be large.…”

Section: Psychophysical Performance Differs With Visual Field Positionmentioning

confidence: 99%

Modeling visual performance differences ‘around’ the visual field: A computational observer approach

2019

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Visual performance depends on polar angle, even when eccentricity is held constant; on many psychophysical tasks observers perform best when stimuli are presented on the horizontal meridian, worst on the upper vertical, and intermediate on the lower vertical meridian. This variation in performance 'around' the visual field can be as pronounced as that of doubling the stimulus eccentricity. The causes of these asymmetries in performance are largely unknown. Some factors in the eye, e.g. cone density, are positively correlated with the reported variations in visual performance with polar angle. However, the question remains whether these correlations can quantitatively explain the perceptual differences observed 'around' the visual field. To investigate the extent to which the earliest stages of vision-optical quality and cone density-contribute to performance differences with polar angle, we created a computational observer model. The model uses the open-source software package ISETBIO to simulate an orientation discrimination task for which visual performance differs with polar angle. The model starts from the photons emitted by a display, which pass through simulated human optics with fixational eye movements, followed by cone isomerizations in the retina. Finally, we classify stimulus orientation using a support vector machine to learn a linear classifier on the photon absorptions. To account for the 30% increase in contrast thresholds for upper vertical compared to horizontal meridian, as observed psychophysically on the same task, our computational observer model would require either an increase of~7 diopters of defocus or a reduction of 500% in cone density. These values far exceed the actual variations as a function of polar angle observed in human eyes. Therefore, we conclude that these factors in the eye only account for a small fraction of differences in visual performance with polar angle. Substantial additional asymmetries must arise in later retinal and/or cortical processing.

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An Accurate Method for Determining the Conspicuity Area Associated With Visual Targets

Abstract: The findings are applicable to industries in which target detectability needs to be assessed in order to either reduce (e.g., for camouflage) or enhance detectability (e.g., road safety).

Cited by 10 publications

References 30 publications

Asymmetries in visual acuity around the visual field

Asymmetries in visual acuity around the visual field

Isoeccentric locations are not equivalent: The extent of the vertical meridian asymmetry

Modeling visual performance differences ‘around’ the visual field: A computational observer approach

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