Relative magnitude of apparent misalignment in acute-angle and oblique-line figures

Day, R. H.; Dickinson, R. G.

doi:10.3758/bf03202996

Cited by 8 publications

(3 citation statements)

References 3 publications

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“…For the time being, it is sufficient to suggest that figure-relative states might determine, in part, apparent misalignment, apparent inexact bisection, and other expressions of apparent displacement in line figures. It can be noted that an essentially similar interpretation of apparent misalignment was briefly suggested earlier (Day & Dickinson, 1979).…”

Section: Resultssupporting

confidence: 64%

Apparent displacement of lines and dots in a parallel-line figure: A clue to the basis of the Poggendorff effect

Day

Kasperczyk

1985

Perception & Psychophysics

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Three experiments involving a parallel-line figure are reported. In the first and second experiments, the Tolansky version of the Poggendorff illusion, apparent inexact bisection of the space between two lines by a third line, was shown to occur with both dots and lines in combination and with three dots. The effect with three dots on the parallels was as great as that with three lines intersecting the parallels. In the third experiment, a variant of the conventional Poggendorff illusion, apparent misalignment of vertical collinear lines, was also shown to occur with dot-line combinations and dots and to be as great with two dots as with two lines. The occurrence of both versions ofthe illusion to the same degree with dots on the parallels as with lines intersecting them serves to rule out explanations of apparent displacement based on changes in the apparent orientation of lines and the apparent size of angles. The Poggendorff and Tolansky effects with only dots also raises questions about explanations couched in terms of depth processing. These questions are discussed and an alternative explanation in terms of a compromise between objective and figure-relative bisection and alignment is tentatively suggested.The original version of the Poggendorff illusion in which two collinear obliques separated by a pair ofparallels appear displaced from their physical alignment is shown in Figure 1A. The upper-right oblique appears to be too high on the right parallel to be aligned with the lower-left oblique on the left parallel. This effect has been variously attributed to optically induced distortion in the region of the intersections (Chiang, 1968;Glass, 1970

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Section: Resultssupporting

confidence: 64%

Apparent displacement of lines and dots in a parallel-line figure: A clue to the basis of the Poggendorff effect

Day

Kasperczyk

1985

Perception & Psychophysics

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“…The Poggendorff illusion is a clear example of this confounding of several distinct phenomena. For example, the reason why the Poggendorff figure is usually presented with the parallels vertical is that the illusion is most striking in this orientation: the effect is reduced if the figure is rotated through 90° (Day & Dickinson, 1979) Hotopf and Hibberd (1989) cogently argued that this is because the Poggendorff illusion combines at least two effects: one is the effect that is seen with the figure in any orientation; the other is the orientation-dependent Zehender (1899) effect, which causes virtual 45° lines to be estimated as closer to the vertical than in fact they are. Failure to factor out the Zehender component has led to the mistaken conclusion that acute angle intersections cannot have anything to do with the Poggendorff effect.…”

Section: Introductionmentioning

confidence: 99%

The Poggendorff illusion: a bias in the estimation of the orientation of virtual lines by second-stage filters

Morgan

1999

Vision Research

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The veridical perception of collinearity between two separated lines is distorted by two parallel lines in the space between them (the Poggendorff illusion). This paper tests the conjecture that the perception of collinearity of separated lines is based on a two-stage mechanism. The first stage encodes the orientation of the virtual line between the proximal terminators of the target lines. The second stage compares this virtual orientation with the orientation of the target lines themselves. Errors can and do arise from either process. Two parallel lines, abutting against the target lines, cause the classical Poggendorff misalignment bias. The magnitude of the bias is increased by Gaussian blur, as is a version of the Poggendorff figure containing only acute angles. In the obtuse-angle figure, on the other hand, blur decreases the misalignment bias. We argue that the acute- and obtuse-angle biases depend upon different mechanisms, and that the obtuse-angle effect is more related to the obtuse-angle version of the Muller-Lyer illusion, which is also decreased by blur. If observers attempt to match the orientation of the virtual line between the two line intersections in the Poggendorff figure they make an error in the same direction as the Poggendorff bias. The orientation of the target lines in the figure, however, is veridically matched to a Gabor-patch probe, unless the target lines are very short, in which case the error is in the same direction as the Poggendorff bias. A small bend in the target lines where they abut the parallels increases the Poggendorff bias if it makes the line more orthogonal to the parallel, but has little effect in the opposite direction. The Poggendorff bias is unlikely to depend upon biases in first-stage linear filters because (a) it still exists in figures composed of short, luminance-balanced lines which are defined by contrast only; and (b) it also exists if the parallels are replaced by grating patches with the same mean luminance as the background. The orientation of the grating in the latter case affects the magnitude of the bias, but even an orientation which should reverse the Poggendorff bias by the mechanism of cross-orientation inhibition fails to do so. The Poggendorff bias is a complex effect arising from several sources. Blurring in second-stage filters with large receptive fields can explain many aspects of the phenomenon.

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“…It is argued that these experiments have not demonstrated that the two dependent variables-alignment and length judgments-are correlated, or that one error causes the other; and it is argued that QuinaHolland's theory of parallel attraction to explain the illusion is not tenable. that positive errors occur when the parallels are very much longer than the obliques (Day & Dickinson, 1979;Wenderoth & Johnson, 1981). One hypothesis to explain this difference is that the "gestalt" of the figure in the first case ( Figure 1C) seduces observers into using a novel stratagem which they do not use with other configurations.…”

mentioning

confidence: 99%

Visual illusions with acute and obtuse angles: Configurational effects and observer strategies

Wenderoth

Johnson

1982

Perception & Psychophysics

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In three experiments, it is demonstrated that the negative Poggendorff illusions that Restle (1969) and others have reported are a special case, that, in general, acute-and obtuse-angle effects are the same, that there are additional special cases which modulate the illusion, but only slightly, and that these special cases derive from particular configurations which impose other effects, including observer strategies, on the basic illusion. These additional effects do not bear necessarily upon the fundamental explanation of the illusion. The experiments also show that effects obtained with amputated illusory figures are not linearly additive. Recent experiments that have measured apparent oblique separation in the Poggendorff figure and have found large obtuse-angle but small, or negative, acute-angle effects are also discussed. It is argued that these experiments have not demonstrated that the two dependent variables-alignment and length judgments-are correlated, or that one error causes the other; and it is argued that QuinaHolland's theory of parallel attraction to explain the illusion is not tenable.

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Relative magnitude of apparent misalignment in acute-angle and oblique-line figures

Cited by 8 publications

References 3 publications

Apparent displacement of lines and dots in a parallel-line figure: A clue to the basis of the Poggendorff effect

Apparent displacement of lines and dots in a parallel-line figure: A clue to the basis of the Poggendorff effect

The Poggendorff illusion: a bias in the estimation of the orientation of virtual lines by second-stage filters

Visual illusions with acute and obtuse angles: Configurational effects and observer strategies

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