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Publication# When bigger is better

Abstract

One of the main factors of crowding is the spacing between target and flankers. The closer the flankers are to the target, the stronger is crowding. Recently, it was proposed that crowding strength is determined by the distance between target and flanker centroids (Levi & Carney, 2009). Here, we determined vernier offset discrimination in the periphery with different flanker configurations. When the vernier was flanked by two vertical lines, thresholds increased. Thresholds decreased compared to the two-lines condition when each of the lines was complemented to form a rectangle. This is in line with the centroid hypothesis because the rectangles' centroids are further away than the centroids of the single flankers. However, when crossing the upper and lower horizontal lines of the rectangles, performance deteriorated even though centroids are the same in this and the rectangle condition. These results can neither be explained by the spacing between the target and the flankers nor by centroid distance. Also simple pooling models fail to account for these results. We propose instead that grouping is a key factor in crowding: crowding decreases when target and flankers ungroup, crowding increases when target and flankers group.

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Related concepts (15)

Related publications (1)

Skew lines

In three-dimensional geometry, skew lines are two lines that do not intersect and are not parallel. A simple example of a pair of skew lines is the pair of lines through opposite edges of a regular tetrahedron. Two lines that both lie in the same plane must either cross each other or be parallel, so skew lines can exist only in three or more dimensions. Two lines are skew if and only if they are not coplanar. If four points are chosen at random uniformly within a unit cube, they will almost surely define a pair of skew lines.

Centroid

In mathematics and physics, the centroid, also known as geometric center or center of figure, of a plane figure or solid figure is the arithmetic mean position of all the points in the surface of the figure. The same definition extends to any object in n-dimensional Euclidean space. In geometry, one often assumes uniform mass density, in which case the barycenter or center of mass coincides with the centroid. Informally, it can be understood as the point at which a cutout of the shape (with uniformly distributed mass) could be perfectly balanced on the tip of a pin.

Trilinear coordinates

In geometry, the trilinear coordinates x : y : z of a point relative to a given triangle describe the relative directed distances from the three sidelines of the triangle. Trilinear coordinates are an example of homogeneous coordinates. The ratio x : y is the ratio of the perpendicular distances from the point to the sides (extended if necessary) opposite vertices A and B respectively; the ratio y : z is the ratio of the perpendicular distances from the point to the sidelines opposite vertices B and C respectively; and likewise for z : x and vertices C and A.

Michael Herzog, Bilge Sayim, Mauro Manassi

The spacing between target and flankers is one of the main factors of crowding. The closer the flankers are to the target, the stronger is crowding. Recently, it was proposed that crowding strength is determined by the distance between target and flanker c ...

2011