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At least 991 records · Page 55Linked to original sources
PubMed1991

Is there a preferred coordinate system for perception of hand orientation in three-dimensional space?

The purpose of this experiment was to determine the preferred coordinate system for representation of hand orientation in 3-dimensional space. The ability of human subjects to perceive angles of the hand in 3-dimensional space (elevation, yaw, roll angles-extrinsic coordinate system) was compared to their ability to perceive hand angles relative to the proximal upper limb segments (wrist joint angles, forearm pronation-intrinsic coordinate system). With eyes closed, subjects performed a matching task in which the experimenter positioned the left arm, forearm and hand and the right arm and forearm. Subjects were then told to match an angle in one of the two coordinate systems by moving only the right hand at the wrist or the forearm as in pronation or roll matching. Absolute constant error (ACE), variable error (VE) and normalized variable error (NVE-normalized to tested range of motion) of matching were quantified for each subject for each of the six angles matched. It was hypothesized that matching angles in a preferred coordinate system would be associated with lower ACE, VE and NVE. Overall, ACE and VE were lower for matching hand angles in the intrinsic coordinate system. This suggests that the preferred coordinate system involved specification of hand angles relative to forearm and arm angles (joint angles) rather than the hand angles relative to axes external to the upper limb. However, matching of pronation angles was associated with larger VE and NVE than roll angle matching. There were no significant differences in ACE between pronation and roll matching. In a second experiment subjects with their forearms constrained at different elevations matched hand elevation and wrist flexion angles. Thus, errors in matching the angles in the non-preferred coordinate system were predictable if the subjects were biased toward matching angles in the preferred coordinate system. Trends in the data suggested that subjects preferred matching hand elevation angles but these trends were not consistent within or between subjects. Thus a preferred intrinsic coordinate system for wrist flexion matching was not observed in this experiment. We suggest that matching angles when proximal limb segments are constrained is a simpler task for the subjects (VE lower than in the first experiment) and may bias the matching toward the extrinsic coordinate system. Thus, hand orientation in 3-dimensional space may be perceived as follows: wrist flexion and abduction angles together with forearm elevation and yaw are used to specify hand elevation and yaw; these together with hand roll angle, completely specify the hand angle in 3-dimensional space.

Adult↗
PubMed1976

Determinants of personal space in young children: perception of distance cues.

Two methods of assessing personal space in young children were examined in a group of 24 boys and 24 girls, aged 3 to 6 yr. When sex of peer figures and affect attributed to them were varied, 3-yr.-olds made distance-cue judgements based on affect but failed to use affect cues in structuring personal space. However, 4- to 6-yr.-olds readily perceived and used distance to communicate the affective quality of peer relations. On both measures, perception of distance cues increased with age. Only girls also used sex of figures as a social cue in depicting appropriate distances.

Affect↗
PubMed2003

Interpretation of a discontinuity in the sense of verticality at large body tilt.

Results of earlier spatial-orientation studies focusing on the sense of verticality have emphasized an intriguing paradox. Despite evidence that nearly veridical signals for gravicentric head orientation and egocentric visual stimulus orientation are available, roll-tilted subjects err in the direction of the long body axis when adjusting a visual line to vertical in darkness (Aubert effect). This has led to the suggestion that a central egocentric bias signal with fixed strength and direction acts to pull the perceived vertical to the subjects' zenith (M-model). In the present study, the subjective visual vertical (SVV) was tested in six human subjects, across the entire 360 degrees range. For comparison, body-tilt estimates from four subjects where collected in a separate series of experiments. For absolute tilts up to approximately 135 degrees, SVV responses showed a gradually increasing Aubert effect that could not be attributed to errors in perceived body tilt but was nicely in line with the M-model. At larger absolute tilts, SVV errors abruptly reversed sign, now showing a pattern concordant with errors in body-tilt estimates but incompatible with the M-model. These results suggest that, in the normal working range, the perception of external space and the perception of body posture are based on different processing of body-tilt signals. Beyond this range, both spatial-orientation tasks seem to rely mainly on a common tilt signal.

Adult↗