DISSOCIATION BETWEEN PERCEPTION AND VISUOMOTOR TRANSFORMATION DURING REPRODUCTION OF REMEMBERED DISTANCES

1. In complete darkness subjects were presented with two visual stimul i whose distance was randomly varied. The subjects were required to re produce the interstimulus remembered distance in two conditions. In on e condition (reproduction by pointing) they pointed to a virtual posit ion in space. In the other condition (visual reproduction) they used t wo other visual stimuli. One of them was fixed, and the other could be manually moved. Constant and variable errors were measured in the two conditions. 2. Constant error varied between the two conditions. In t he pointing task subjects slightly overestimated the shorter distances , and underestimated the longer ones. During visual reproduction, they consistently overestimated all distances, and the error of overestima tion tended to increase with distance. Statistical comparison between the errors in the two conditions was significant. Variable error incre ased with distance in both conditions, but did not show any significan t difference between the two tasks. 3. The results of the present expe riment support the hypothesis that perception and visuo-motor transfor mation are two separate processes in which the same object attributes are independently analysed. However, the finding that variable error d id not change between the