9 Egocentric Referents in Human Limb Orientation (original) (raw)

Advances in Psychology, 1980

Abstract

Testing the hypothesis that spatial localization is made on the basis of an abstract spatial code, rather than on stored proprioceptive information, orientation of the unseen limb was contrasted under same and switched limb movement conditions. In Experiments 1 and 2, movements were executed in the midline vertically upward and horizontally away, respectively. The results of both experiments revealed that same limb accuracy was superior only at farther target positions, and it was hypothesized that orientation of the limb could be mediated by a spatial location code if movements remained within the confines of an egocentric reference system. To test this tentative assertion more directly, Experiment 3 examined same and switched limb performance in two-dimensional space. At locations defined a priori as inside egocentric space, absolute movement accuracy and amplitude error failed to differentiate between same and switched limb localization. At locations defined a priori as outside egocentric space the same limb condition prevailed. Meanwhile, irrespective of spatial position directional error revealed that same limb orientation was superior to switched limb orientation. The amplitude error findings were interpreted to mean that body referent points inside egocentric space allow for the parameterization of the necessary length-tension relationships in the agonist and antagonist muscles of either limb. The direction findings were explained in light of previous data demonstrating systematic perceptual errors in estimating the objective referents.

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