Perceived orientation of isolated line segments

Bouma, H Herman; Andriessen, JJ

doi:10.1016/0042-6989(68)90091-6

Cited by 120 publications

(74 citation statements)

References 18 publications

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“…In any case, the alignment error still present in the control condition seems to point out the occurrence of a general alignment error concerning the oblique orientation, or of an apparent elongation of the vertical extent between the obliques, although it is less evident than in Experiment I (d. Appelle, 1972;Bouma & Andriessen, 1968;Day & Dickinson, 1976).…”

Section: Resultsmentioning

confidence: 66%

The orientation of a parallel-line texture between the verticals can modify the strength of the Poggendorff illusion

Masini

Sciaky

Pascarella

1992

Perception & Psychophysics

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In the present experiments, we attempted to evaluate the modification of the strength of the Poggendorff illusion as a function of the different orientation of a parallel-line texture filling the space between the vertical lines. In Experiment 1, the standard version of the PoggendorfI configuration was tested against four different parallel-line textures oriented at 0 0 , 4 5 0 , 90 0 , and 135 0 with respect to the obliques. The results showed that the illusory effect was a linear function of the progressive discrepancy between the angle of the lines of the texture and that of the obliques. In Experiment 2, we tested the same textures used in Experiment 1 after the elimination of the two vertical lines. The data obtained approximated a linear function, as in the previous experiment, but the alignment errors were consistently lower. The statistical analysis performed on the data of all eight experimental conditions shows that both factors-texture and presence/absence of verticals-were significant, but most of the effect was due to the texture factor. The results may be interpreted through the "perceptual compromise hypothesis," originally proposed for the bisection forms of the PoggendorfI illusion, but with important modifications. The data are also discussed in terms of their implications for other theories proposed for the PoggendorfI illusion.The Poggendorff illusion is shown in Figure I; in the original version of this optical-geometrical illusion, two collinear obliques separated by a pair of parallels appear displaced from their physical alignment. In this case, the upper right oblique appears too high to be aligned with the prolongation of the lower left oblique.There are several accepted fmdings on this illusion: The apparent displacement of the transversals is increased when the angles are more acute; increasing the separation between the parallels increases the effect; a horizontal or vertical orientation of the transversal reduces the illusion; and the distortion does not depend on the straightness of the separating elements (Coren & Girgus, 1978).Despite general agreement on these empirical findings, the illusory effect has been explained within different theoretical frameworks. One type of explanation involves "structural factors" like optical blur and lateral inhibition that could induce distortions in the region of the intersections between lines, for example, expansion of acute

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Section: Resultsmentioning

confidence: 66%

The orientation of a parallel-line texture between the verticals can modify the strength of the Poggendorff illusion

Masini

Sciaky

Pascarella

1992

Perception & Psychophysics

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“…These 19th century investigations were, however, descriptive rather than experimental, and the interpretations, speculative. Despite numerous modern studies (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15), the phenomenon of angle misperception has never been explained.…”

mentioning

confidence: 99%

Why are angles misperceived?

Nundy

Lotto²,

Coppola³

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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Although it has long been apparent that observers tend to overestimate the magnitude of acute angles and underestimate obtuse ones, there is no consensus about why such distortions are seen. Geometrical modeling combined with psychophysical testing of human subjects indicates that these misperceptions are the result of an empirical strategy that resolves the inherent ambiguity of angular stimuli by generating percepts of the past significance of the stimulus rather than the geometry of its retinal projection.T he fact that the subtense of any acute angle is seen as being somewhat larger than the measured angle of the stimulus, whereas the subtense of any obtuse angle is seen as being somewhat smaller, was first reported by Wundt (1) and subsequently by both Hering (2) and Helmholtz (3), all of whom surmised that these distortions might underlie some of the classical geometrical illusions (4). These 19th century investigations were, however, descriptive rather than experimental, and the interpretations, speculative. Despite numerous modern studies (5-15), the phenomenon of angle misperception has never been explained.Here we provide evidence that the systematic misperception of angle subtense is the consequence of a radically empirical strategy of perception in which the angle seen is determined by the relative frequency of the possible sources of angle projections that observers have experienced. The biological rationale for this strategy is a solution to the problem posed by the inevitable ambiguity of angular stimuli. The inability of an angle projected onto a plane to specify uniquely the source is illustrated in Fig. 1. Indeed, because space is divisible without limit, the number of possible real-world sources underlying a given retinal projection is infinite.Because the well being of an observer depends on appropriate interactions with the sources of visual stimuli, the ambiguity of retinal images has long been regarded as a central problem in vision (16). Recent studies of simultaneous brightness contrast (17,18), Mach bands (19,20),, and the perception of color (22) have all suggested that this dilemma is solved by an empirical strategy in which retinal activation triggers associations (percepts) determined by the relative frequencies of the possible sources of the stimulus in past experience. A limitation in validating this concept of vision has been the practical difficulty of quantifying the frequency distribution of the real-world sources underlying the various categories of visual experience. (This problem has also been an obstacle to psychologists who have sought to model perception in terms of Bayes' decision theorem; see ref. 23 for a recent review.) Examining the perception of oriented lines circumvents this obstacle in that the frequency distribution of the possible sources of a given retinal projection-for example, the subtense of the typical source of a given angle projected on the retina-can be computed by geometrical principles, thus providing a more concrete basis for predicting perceptual...

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“…Whether the reference frame is physically present or implied in the stimulus display, stimulus elements tend to become organized with respect to it. For example, in the perceptual literature, it is well known that the perceived orientation of an isolated test line tends to be drawn toward the nearest cardinal axis (Andrews, 1967;Bouma & Andriessen, 1968;seeHoward, 1982). Similarly, many visual illusions (including, e.g., the well-known Miiller-This research was supported in part by AFSOR Grant 89-<J076 to Stanford University.…”

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confidence: 99%

Structure and strategy in encoding simplified graphs

Schiano

Tversky

1992

Mem Cogn

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Tversky and found a systematic bias toward the 45 0 line in memory for the slopes of identical lines when embedded in graphs, but not in maps, suggesting the use of a cognitive reference frame specifically for encoding meaningful graphs. The present experiments explore this issue further using the linear configurations alone as stimuli. Experiments 1 and 2 demonstrate that perception and immediate memory for the slope of a test line within orthogonal "axes" are predictable from purely structural considerations. In Experiments 3 and 4, subjects were instructed to use a diagonal-reference strategy in viewing the stimuli, which were descrfbed as "graphs" only in Experiment 3. Results for both studies showed the diagonal bias previously found only for graphs. This pattern provides converging evidence for the diagonal as a cognitive reference frame in encoding linear graphs, and demonstrates that even in highly simplified displays, strategic factors can produce encoding biases not predictable solely from stimulus structure alone.

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Perceived orientation of isolated line segments

Cited by 120 publications

References 18 publications

The orientation of a parallel-line texture between the verticals can modify the strength of the Poggendorff illusion

The orientation of a parallel-line texture between the verticals can modify the strength of the Poggendorff illusion

Why are angles misperceived?

Structure and strategy in encoding simplified graphs

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