Manual matching of perceived surface orientation is affected by arm posture: evidence of calibration between proprioception and visual experience in near space

Abstract

Proprioception of hand orientation (orientation production using the hand) is compared with manual matching of visual orientation (visual surface matching using the hand) in two experiments. In experiment 1, using self-selected arm postures, the proportions of wrist and elbow flexion spontaneously used to orient the pitch of the hand (20 and 80%, respectively) are relatively similar across both manual matching tasks and manual orientation production tasks for most participants. Proprioceptive error closely matched perceptual biases previously reported for visual orientation perception, suggesting calibration of proprioception to visual biases. A minority of participants, who attempted to use primarily wrist flexion while holding the forearm horizontal, performed poorly at the manual matching task, consistent with proprioceptive error caused by biomechanical constraints of their self-selected posture. In experiment 2, postural choices were constrained to primarily wrist or elbow flexion without imposing biomechanical constraints (using a raised forearm). Identical relative offsets were found between the two constraint groups in manual matching and manual orientation production. The results support two claims: (1) manual orientation matching to visual surfaces is based on manual proprioception and (2) calibration between visual and proprioceptive experiences guarantees relatively accurate manual matching for surfaces within reach, despite systematic visual biases in perceived surface orientation.

Figure 1

Biomechanical data from the visual surface matching task. The upper left panel (A) illustrates the VICON markers (drawn to scale) attached to the hand and arm, and defines the elbow and wrist angles. The upper right panel (B) shows the average arm postures of all participants in the visual surface orientation matching task. Each set of four dots of the same color represent the VICON markers. Different colors represent different visual slant conditions. In the lower panels, the mean elbow angle (C) and mean wrist angle (D) are plotted as functions of mean central hand orientation for the visual surface orientation matching task. Standard errors of the means are shown.

Figure 2

Posture as a function of elbow use during the visual surface matching task. Average arm postures of the Elbow Group (A) and Wrist Group (B). Mean elbow angle (C) and mean wrist angle (D) plotted as functions of mean central hand orientation for the Elbow Group (open circles) and Wrist Group (solid circles). Standard errors of the means are shown.

Figure 3

Mean central hand orientation plotted as a function of the physical slant for the visual surface orientation matching task. Open circles represent the Elbow Group (N=16). Solid circles represent the Wrist Group (N=5). Standard errors of the means are shown.

Figure 4

Orientation production data. A. Mean central hand orientation plotted as a function of the indicated orientation for the orientation production task. A polynomial fit (cubic) is shown. B. Comparison between visually perceived surface orientation (solid circles; estimation data from Durgin, Li and Hajnal 2010; Experiment 1) and proprioceptively perceived (verbally requested) hand pitch orientation (open circles). A polynomial (cubic) fit of the visually perceived slant is shown. Standard errors of the means are shown.

Figure 5

Illustration of the apparatus and arm postures used in Experiment 2. Left panel: wrist restriction condition (Elbow Group). Right panel: elbow restriction condition (Wrist Group).

Figure 6

Mean central hand orientation plotted as a function of the physical surface orientation for the visual surface orientation matching task. Standard errors of the means are shown.

Figure 7

Mean central hand orientation plotted as a function of the indicated orientation for the proprioceptive orientation production task. Standard errors of the means are shown.

Figure 8

Illustration of the actual and predicted manual matching performance upper right (see the main text for detailed explanation), based on numeric estimates of visual and proprioceptive slant.