Angle-Matching Illusions and Perceived Line Orientation

Abstract

Spatial illusions which occur in angle-matching tasks were examined in six experiments using two different kinds of display. In experiments 1 and 2 illusory errors generally were in the direction predicted by Lennie's hypothesis which states that angle arms are attracted perceptually towards the oblique axes of space, although the display used in these experiments differed from Lennie's. However, experiment 3 showed that these errors might equally be explained by the addition of interactive effects between angle arms (tilt illusions). Parametric investigation of Lennie's figures (experiments 4 and 5) showed that thelargest angular illusion occurred with the largest angle used (45 degrees) and an intermediate line length (2 deg 7 min). These angular illusions were not explicable by the addition of tilt illusions (experiment 6), suggesting that different judgmental processes may underlie orientation and angle estimation.

The roles of axes of symmetry in orientation illusions

“…It is known that the perceived orientation of a line is changed by the proximity of another line at a different orientation (Blakemore et al, 1970;Bouma & Andriessen, 1970;Wenderoth & White, 1979). It might be argued, then, that the effects that have been observed are due not to the axes of bilateral symmetry directly, but rather to the cumulative change in the perceived orientation of a line induced by two nearby lines at different orientations.…”

“…It might be argued, then, that the effects that have been observed are due not to the axes of bilateral symmetry directly, but rather to the cumulative change in the perceived orientation of a line induced by two nearby lines at different orientations. There is considerable evidence that this is not the case (Wenderoth, 1973(Wenderoth, , 1974Wenderoth & Beh, 1977;Wenderoth & Curthoys, 1974;Wenderoth & White, 1979). For example, Wenderoth (1973) and Wenderoth and Curthoys (1974) showed that a single inducing line tilted 30 deg left or 60 deg right of vertical resulted in an apparent clockwise displacement of a test line.…”

The effects of angle-arm length on judgments of angle magnitude and orientation contrast

“…No errors occur in matching two angles when the angles differ only in that one has its bisector oriented horizontally and the other has its bisector oriented vertically (Lennie, 1971;Wenderoth & Johnson, 1982;Wenderoth & White, 1979). In Experiment 1, therefore, we varied the inclination of one angle's arms until that angle appeared to match another angle whose arms were either shorter, equal to, or longer than the variable angle's arms.…”

Expansion and contraction of outline and solid acute angles: Effects of angle magnitude, type of display, and the nature of the matching task

“…tation domain may not predict those in the angular domain, despite the fact that, in Euclidean terms, the physical size of an acute angle equals the difference in absolute orientation between the angle's arms (Emerson, Wenderoth, Curthoys, & Edmonds, 1975;Wenderoth & Johnson, 1984;Wenderoth & White, 1979). Two recent studies have concluded that three perceptual domainsorientation, position, and collinearity (straightness)-are independent, at least in part.…”