Assessing Poggendorff effects via collinearity, perpendicularity, parallelism, and Oppel (distance) experiments

Abstract

By adjusting the orientation of, and separation between, two free-standing dots, Ss indicated directions and distances associated with the Poggendorff display (a transversal interrupted by parallel lines). Judged distance between parallels (with transversal absent) increased slightly when additional interior parallels were added; this Oppel effect can be interpreted as contour repulsion. Errors in judging the orientation of an actual transversal segment were too small to account for the Poggendorff effect. The usual large errors occurred for estimates of the orientation of the missing transversal segment between the parallel lines. Cognitive mistracking adequately describes the Poggendorff effect. Mistracking is a function of the angle subtended between transversal and parallels, and of the orientation of the entire display.The traditional Poggendorff display consists of two parallel lines interrupting a transversal; the transversal segments do not appear collinear. Contour-interaction theories claim that perception is distorted by the displacement of the neural representation of the contours forming the physical stimulus. For example, the Poggendorff effect is logically explained by postulating that parallels appear too close, i.e., through lateral interactions, neural contours attract one another (discussed by Tong & Weintraub, 1974). Alternatively, the acute angle between transversal and parallels might appear too large, an instance of contour repulsion (Blakemore. Carpenter, & Georgeson, 1970;Burns & Pritchard, 1971).The initial experiments are direct offshoots of our previous work (Tong & Weintraub, 1974), attempting .to assess the parallels-attract hypothesis applied to the Poggendorff effect. If parallels between transversal segments are represented in experience as too close together, then the attached transversals will seem to be vertically misaligned when they are actually collinear. Additional parallel lines were added between the original parallels under the assumption that the additional parallels would cause increasing contour attraction and therefore an increasing Poggendorff effect. However, the data clearly showed that extra interior parallels reduced the Poggendorff error (Tong & Weintraub, 1974). The Oppel effect (Robinson, 1972), the overestimation of filled space relative to unfilled space, seemed able to account for the findings. The Poggendorff display containing extra parallels is directly analogous to an Oppel display containing many interior line segments parallel to end segments defining an interval. The first two experiments continue the investigation of the role of the parallels. EXPERIMENT I MethodThe paid Ss were 40 students at the University of Michigan, tested one at a time. Each S received eight white stimulus sheets, 21.6 x 27.9 em (8 1 / , x II in.) containing Multilithed black lines and dots. Vertical lines, .4 mm wide, were drawn parallel to the longer edges of a sheet. The separation between outer parallels was either 32 or 42'13 mm. (These choices were dictated by the sepa...

The logic of misperceived distance (or location) theories of the Poggendorff illusion

“…The statement concerning "apparent elongation ofthe part of the parallel forming an obtuse angle with the transversal" implies a vertical component for the perceptual displacement vector; d alone does not permit the determination of a unique pdv with that property. Weintraub and Tong (1974) reported dot-distance and dot-orientation information in conjunction with vertical displacement settings, E, that achieved perceptual collinearity directly on the Poggendorff display. A convenient alteration of the typical Poggendorff display omitted the right transversal segment.…”

“…Thus, a pair of free-standing dots was used to measure several orientations (tilts) and lengths perceptually. Figure 4, reproduced from Weintraub and Tong (1974), depicts the orientation (directional) errors in degrees derived from free-standing dots. Three conditions are of primary interest.…”

“…Instead, the C data show somewhat smaller but very similar errors to [C] that were measured on the display . Figure 5 (which includes the relevant directional errors from Figure 4) transforms the Weintraub and Tong (1974) data into perceptual-displacement terms (the three different transversals oriented at three different A angles plotted in one figure to facilitate comparisons). Figure 3B is the appropriate graphical representation (perceptual collinearity achieved).…”

“…Trueman & Wilson, 1989). Greist-Bousquet and Schiffman (1981), Trueman and Wilson (1989), and Weintraub and Tong (1974) have employed a dot-setting task that permits the observer to set the distance and orientation between a pair of free-standing dots to match perceptually the intertransversal slant distance and direction in a Poggendorff display. Wilson and Pressey's (1976) method precludes perceived orientation judgments by requiring all dot settings to be oriented horizontally.…”

The relation between apparent extent and alignment in the Poggendorff illusion: A response to “No evidence for apparent extent between parallels as the basis of the Poggendorff effect,” by Day, Jolly, and Duffy

“…Furthermore, other investigators have found underestimation of inner oblique extent when subjects produce (GreistBousquet & Schiffman, 1981a;Weintraub & Tong, 1974), adjust (Judd, 1899), or compare (Quina-Holland, 1977 stimuli that are equivalent in content and orientation (i.e., an unfilled oblique extent). Dayet al (1987) extend these findings of underestimation to diagonally oriented versions of the Poggendorff illusion (e.g., see Figure SA).…”