The basis of the Bourdon illusion

Wenderoth, Peter

doi:10.3758/bf03205998

Cited by 3 publications

(4 citation statements)

References 21 publications

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“…It is important in this context that the illusions also occur when the two thin triangles are placed side by side with their edges parallel and at an angle with their edges at right angles (Wenderoth, 1991). These arrangements result in illusions of nonparallelness and nonright angularity, respectively (Day et aI., 1990).…”

Section: Discussionmentioning

confidence: 99%

Anomalous orientation effects in the Bourdon illusion

Verstijnen

Leeuwen

1998

Psychonomic Bulletin & Review

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Section: Discussionmentioning

confidence: 99%

Anomalous orientation effects in the Bourdon illusion

Verstijnen

Leeuwen

1998

Psychonomic Bulletin & Review

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“…Wenderoth and O'Connor (1987b) reported that no such second-stage adjustment occurred with truly bent edges. Wenderoth (1990) has proposed that this second-stage adjustment reflects the position effect that can be seen in Figure IA; even were the upper and lower chevron segments set parallel to the adjacent wedge edges, more global inspection of the whole Bourdon figure gives the clear impression that the left-hand upper and lower extremities (i.e., the left edges of the wedge bases) are displaced to the right of the central apices. Thus, in Figure lA, attraction orientation effects and position effects occur in the same direction and reinforce each other.…”

Section: Discussionmentioning

confidence: 99%

“…To measure the effect, Wenderoth, O'Connor, and Johnson (1986a) and Wenderoth andO'Connor (1987a, 1987b) had subjects set a variable chevron, represented by the straight line in Figure lA, to match the apparent bend. When the truly straight edge of the solid Bourdon figure was oriented 22.5°clockwise and each vertex anThis research was supported by Australian Research Council Grant A7883l87l to the first author.…”

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confidence: 99%

Determinants of subjective contour: Bourdon illusions and “unbending” effects

Wenderoth

Criss

Zwan

1990

Perception & Psychophysics

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Wenderoth and O'Connor (1987b) reported that, although matches to the straight edge of two triangles placed apex to apex revealed an apparent bending in the direction of the chevron formed by the hypotenuse pair (the Bourdon effect), no perceptual unbending of the bent chevron occurred. Using subjective contour figures, Walker and Shank (l988b) found large and approximately equal bending and unbending effects, consistent with two theories that they proposed. In Experiment 1, using adjustable chevron matching and subjective contours, we found that Bourdon effects, equivalent in magnitude to those reported by Walker and Shank, were 4-5 times larger than unbending effects. In Experiment 2, we used a variation of Walker and Shank's measurement technique, in which subjects selected a matching angle from a graded series. We obtained Bourdon effects similar to those in Experiment 1, but much larger unbending effects. Nevertheless, Bourdon effects were significantly larger than unbending effects in one set of data; and in another, Bourdon test means were larger than unbending test means. In both data sets, there was a large and significant pretest bending effect, which enhanced the magnitude of unbending test minus pretest scores. These results were consistent with our theory but not the theories of Walker and Shank. The variance of unbending test matches, 3-4 times that of Bourdon test matches, reflected the task difficulty. We propose that subjective obtuse angle contraction that exceeds real obtuse angle contraction explains the fact that unbending effects are larger in subjective than in real contours.

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“…According to another explanation put forward by Wenderoth et al (1986) (see also Wenderoth, 1991), every stimulus is processed along three separate neural channels coding orientation, position, and collinearity. These authors postulated that the illusion arises from conflicting signals between these channels.…”

Section: Previous Explanations For the Bourdon Illusionmentioning

confidence: 99%

Optimizing the strength of the Bourdon effect by varying the triangle arrangement

Devinck¹,

Quaireau²

2021

Atten Percept Psychophys

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The Bourdon illusion refers to the perceived bentness of the straight collinear edges when two right-angled triangles are placed apex to apex. We studied this illusion using a cancellation method. In the first of three experiments, we manipulated the apex angle, with six different angles ranging from 4°to 45°. Results indicated that the Bourdon illusion is strongest when the angle is around 12°. In the second experiment, we compared four scalene triangles with a right-angled triangle. The angular shift was most salient when the shape corresponded to a right-angled triangle. In the third experiment, the patterns were created by varying the size of one right-angled triangle while holding the size of the second right-angled triangle constant. Results indicated that the Bourdon illusion was strongest when both right-angled triangles were of equal size. Our data suggest that the Bourdon illusion depends critically upon the specific arrangement of shapes in the display.

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The basis of the Bourdon illusion

Abstract: Day (1990) and Day, Mitchell;and Stecher (1990) Wenderoth, Criss, and van der Zwan (1990), Wenderoth and O'Connor (1987a, 1987b), and Wenderoth, O'Connor, and Johnson (1986 Day (1990) and Day et aL (i990).

Cited by 3 publications

References 21 publications

Anomalous orientation effects in the Bourdon illusion

Anomalous orientation effects in the Bourdon illusion

Determinants of subjective contour: Bourdon illusions and “unbending” effects

Optimizing the strength of the Bourdon effect by varying the triangle arrangement

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