Academic journal article Psychonomic Bulletin & Review

The Role of Contextual Cues in the Haptic Perception of Orientations and the Oblique Effect

Academic journal article Psychonomic Bulletin & Review

The Role of Contextual Cues in the Haptic Perception of Orientations and the Oblique Effect

Article excerpt

Blindfolded right-handed participants were asked to position, with the right hand, a frontoparallel rod to one of three orientations: vertical (0°) and left 45° and right 45° obliques. Simultaneously, three different backgrounds were explored with the left hand: smooth, congruent stripes (parallel to the orientation to be produced), or incongruent stripes (tilted relative to the orientation to be produced). The analysis of variable errors showed that the oblique effect (higher precision for the vertical orientation than for the oblique orientations) was weakened in the presence of contextual cues, because of an improvement in oblique precision. Moreover, the analysis of constant errors revealed that the perception of orientations erred in the direction of the stripes, similar to the effect that has been found with vision, where visual contextual cues (tilted frame or lines) divert the perception of the vertical. These results are discussed in relation to a patterncentric frame of reference hypothesis or as a congruency effect.

In this study, we address the question of whether contextual cues are integrated in the haptic (tactualkinesthetic) perception of orientations by humans. Previous experiments have provided clear evidence that orientation processing differs according to the value of the orientation. Indeed, the vertical orientation is perceived more precisely than oblique orientations (for reviews, see Gentaz, 2000; Gentaz & Ballaz, 2000; Gentaz & Tschopp, 2002). This anisotropy, called the oblique effect by Appelle (1972), is present whatever the perceptual system involved in the perceptual judgment. It has been found with a great variety of tasks in visual (Attneave & Olson, 1967; Furmanski & Engel, 2000; Gentaz et al., 2001; Luyat & Gentaz, 2002; Mclntyre, Lipshits, Zaoui, Berthoz, & Gurfinkel, 2001; McMahon & MacLeod, 2003; Westheimer, 2003), haptic (Appelle & Countryman, 1986; Gentaz, Badan, Luyat, & Touil, 2002; Gentaz & Harwell, 1995, 1996, 1998, 1999; Gentaz & Streri, 2004; Hermens & Gielen, 2003; Kappers, 1999; Kappers & Koenderink, 1999; Lechelt & Verenka, 1980; Luyat, Gentaz, Regia Corte, & Guerraz, 2001), and somatovestibular (Gentaz et al., 2001) systems.

The oblique effect in haptics has usually been shown with a reproduction-of-orientations task in which blindfolded participants had to scan a rod with one hand and to reproduce the previous orientation with the same or the contralateral hand (Appelle & Countryman, 1986; Gentaz & Hatwell, 1995, 1996, 1998, 1999; Lechelt & Verenka, 1980). Evidence for a similar oblique effect has also been shown with a production task (Gentaz et al., 2002) in which a rod had to be oriented to a given orientation (vertical, horizontal, or oblique) following verbal instructions and without previous coding of the tested orientation. In contrast to the reproduction of orientations that have been previously explored but not verbally defined, performance on the production task appears more likely to be based on internal models of spatial orientations, as has been suggested by previous researchers (Heeley & Buchanan-Smith, 1990; Mclntyre et al., 2001; Morgan, 1991).

Essock (1980) has proposed a distinction between "Class 1 oblique effects," observed when one is measuring the basic functioning of the visual system (acuity or contrast threshold), and "Class 2 oblique effects," observed in paradigms in which cognitive processes involved in identifying, remembering, or categorizing the orientations of stimuli are emphasized. Class 1 effects can be explained consistently by the properties of orientationselective neurons (Li, Peterson, & Freeman, 2003; Westheimer, 2003) and may be tied to a retinocentric frame of reference (Banks & Stolarz, 1975; Chen & Levi, 1996; Corwin, Moskowitz-Cook, & Green, 1977; Furmanski & Engel, 2000; Lennie, 1974; Orban, Vandenbussche, & Vogels, 1984; Saarinen & Levi, 1995). …

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