Eliminating the Haptic Oblique Effect: Influence of Scanning Incongruity and Prior Knowledge of the Standards

Abstract

Although the oblique effect has been conceptualized as a purely visual phenomenon, recent studies report its occurrence in a haptic matching task and present the hypothesis that differences in haptic orientational sensitivity might be responsible for the results. The possibility that procedural variables could be responsible was investigated. Specifically, the effect of prior knowledge of the stimulus orientation standards and of use of bilateral haptic exploration of standard and comparison orientations was examined. The results indicate that the reported oblique effect is reduced either when subjects are not informed which orientations will be tested, or when a unilateral matching procedure instead of a bilateral one is used. When both conditions are combined, the haptic oblique effect is eliminated. It is concluded that this particular manifestation of the oblique effect is not related to haptic sensitivity, but stems from the use of well-established imagery as referent for a match (imagery for oblique stimulus orientations is inferior) and the inherently different scanning patterns required in bilateral exploration of obliques (percepts of standard and comparison obliques will be necessarily different).

Haptic orientation perception benefits from visual experience: Evidence from early-blind, late-blind, and sighted people

“…Appelle and colleagues (Appelle & Countryman, 1986;Appelle & Gravetter, 1985) found that the oblique effect was eliminated when, prior to testing, no visual or verbal knowledge about the stimulus orientations was conveyed to the participants. Appelle and colleagues therefore suggested that visual processing is critically responsible for the oblique effect.…”

“…Remarkably, haptic perception of basic spatial properties such as line length (Lanca & Bryant, 1995;Marks & Armstrong, 1996), path length (Lederman, Klatzky, & Barber, 1985), and orientation (see, e.g., Appelle & Countryman, 1986;Gentaz & Hatwell, 1998, 1999Kappers, 1999;Zuidhoek, Visser, Bredero, & Postma, 2004) is susceptible to marked distortions, at least in blindfolded sighted individuals. Interestingly, the distortions in haptic perception of orientation appear to be both systematic over multiple locations and consistent over different tasks-for example, the setting of a test bar either parallel or collinear with a reference bar, or the pointing of a bar toward a marker (Kappers, 1999(Kappers, , 2002Kappers & Koenderink, 1999).…”

Haptic space processing--Allocentric and egocentric reference frames.

“…Appelle & Countryman, 1986;Appelle & Gravetter, 1985;Gentaz & Hatwell, 1995;Lechelt, Elluk, & Tanne, 1976;Lechelt & Verenka, 1980). In most of these studies, the oblique effect concerns the larger spread in measurements for oblique orientations of a stimulus as compared to cardinal orientations.…”

An ecological approach to cognitive (im)penetrability

“…However, data seem to be more consistent with the continuity thesis. Indeed, the haptic processes that generate the oblique effect do not seem to be modular because it is possible to suppress the occurrence of the haptic oblique effect by changing the stimulus encoding conditions (Appelle & Countryman 1986;Gentaz & Hatwell 1995;. Blindfolded subjects were asked to explore a rod haptically and to reproduce its orientation.…”