Amplitude and direction errors in kinesthetic pointing

Abstract

We investigated the accuracy with which, in the absence of vision, one can reach again a 2D target location that had been previously identified by a guided movement. A robotic arm guided the participant's hand to a target (locating motion) and away from it (homing motion). Then, the participant pointed freely toward the remembered target position. Two experiments manipulated separately the kinematics of the locating and homing motions. Some robot motions followed a straight path with the bell-shaped velocity profile that is typical of natural movements. Other motions followed curved paths, or had strong acceleration and deceleration peaks. Current motor theories of perception suggest that pointing should be more accurate when the homing and locating motion mimics natural movements. This expectation was not borne out by the results, because amplitude and direction errors were almost independent of the kinematics of the locating and homing phases. In both experiments, participants tended to overshoot the target positions along the lateral directions. In addition, pointing movements towards oblique targets were attracted by the closest diagonal (oblique effect). This error pattern was robust not only with respect to the manner in which participants located the target position (perceptual equivalence), but also with respect to the manner in which they executed the pointing movements (motor equivalence). Because of the similarity of the results with those of previous studies on visual pointing, it is argued that the observed error pattern is basically determined by the idiosyncratic properties of the mechanisms whereby space is represented internally.

The perception and representation of orientations: A study in the haptic modality

“…First, the most conspicuous aspect of the systematic error, the bias of most oblique orientations toward the closest diagonal, has been observed in various visual tasks such as reproducing the location of a point in a circle (Huttenlocher et al, 1991;Huttenlocher et al, 2004) and perceiving oriented lines (de Graaf et al, 1994;Lennie, 1971;Smyrmis et al, 2007;Zlatkova, 1993) or random dot patterns (Yakimoff, Lansky, Mitrani, & Radil, 1989). A similar bias has also been observed in pointing tasks toward remembered targets presented in a circular arrangement in the kinesthetic (Baud-Bovy & Viviani, 2004) and visual modalities (e.g., Gordon, Ghilardi, & Ghez, 1995;Gourtzelidis et al, 2001;Smyrmis et al, 2007). Second, our results are also in line with the widespread observation that the reproduction of the vertical and horizontal orientations is more accurate than the reproduction of oblique orientations, which has also been cited in many different visual tasks (e.g., Appelle, 1972;Essock, 1980;Keene, 1963;Westheimer, 2003;Zlatkova, 1993).…”

“…In particular, it does not explain the tendency to overestimate orientations between 0°a nd 90°, and underestimate them between 90°and 180°. Additional factors might be at play such as the viewing angle in the visual modality (Hermens & Gielen, 2003; see also Dick & Hochstein, 1989;Keene, 1963) or a bias in the perceived orientation of the arm segments in the haptic modality (e.g., Baud-Bovy & Viviani, 2004).…”

Central Processes Amplify and Transform Anisotropies of the Visual System in a Test of Visual–Haptic Coordination

“…Oblique effects for response variability have been observed in visual (Bauer et al, 1979;Essock, 1980;Heeley et al, 1997;Gentaz et al, 2001), motor (Baud-Bovy and Viviani, 2004;Smyrnis et al, 2007), and haptic (Lechelt et al, 1976;Baud-Bovy and Gentaz, 2006) perceptual tasks. The role of gravity in defining the vertical axes for oblique effects has been studied by tilting the head and body with respect to gravity (Buchanan-Smith and Heeley, 1993;Lipshits and McIntyre, 1999;Luyat et al, 2001;Luyat and Gentaz, 2002) and by performing these experiments in weightlessness McIntyre, 1999, 2007;Lipshits et al, 2005).…”

“…Accuracy measurements in visual or motor-matching tasks typically reveal biases in responses away from the vertical and horizontal axes (tilt contrast) in both visual (Reese, 1953;Dick and Hochstein, 1989;Yakimoff et al, 1989) and motor (Gordon et al, 1994;Baud-Bovy and Viviani, 2004;Smyrnis et al, 2007) tasks. These effects have variously been ascribed to (1) an exaggeration of deviations away from the meridians (Gibson, 1966;Howard, 1982), (2) attraction of responses toward the diagonal (Yakimoff et al, 1989), or (3) artifacts related to an implicit projection of stimuli in depth (Dick and Hochstein, 1989).…”

Design of a Bio-Inspired 3D Orientation Coordinate System and Application in Robotised Tele-Sonography

“…The oblique effect is also present at the cognitive level (Olson & Hildyard 1977) and is termed "oblique effect of class 2" (Essock, 1980). The same phenomenon has been reported to occur in the kinesthetic perceptual system (Baud-Bovy & Viviani, 2004) and for the motor control (Smyrnis et al, 2007). According to Gentaz (Gentaz, 2005) the vertical axis is privileged because it gives the gravitation direction and the horizontal axis is also privileged because it corresponds to the visual horizon.…”