THE CONTRIBUTION OF VISION AND PROPRIOCEPTION TO JUDGMENTS OF FINGER PROXIMITY

We sought to determine whether an increase in judged egocentric distan ce created by increasing vergence-specified distance would be negated when participants pointed at their own finger. It was found that ocula r position dominates limb proprioception in the judgement of finger di stance in the sagittal plane when vision is available. In contrast, an increase in perceived egocentric distance was largely attenuated by t he presence of limb proprioception in reduced visual cue conditions. W e conclude that the relative contribution of vergence to perceived dis tance depends upon the strength of the vergence effort signal when the re are other cues present. Furthermore, if the distance percept includ es a major contribution from retinal cues, then the visual component w ill dominate the limb proprioception component. If the visual componen t is largely determined by vergence information, limb proprioception w ill make a significant contribution and actually dominate when the ver gence effort signal is weak. The results extend previous studies that have found a similar relationship between ocular position and limb pro prioception in the perception of a finger's location in the coronal pl ane.