Abstract: A set of metalic curved lines was used as stimuli which either tou- ched upon or moved with fast or slow speed across the index finger pad which remained immobile. Six subjects were tested. Their task was to ju- dge the distance between two end-points of the curved line and to repro- duce it on a rule. The basic findings were as follows: Ⅰ. The distance was always underestimated at fast speed, while it could be more accu- rately estimated at slow speed or at immobility ; the apparent distance in the first case was significantly shorter than that in the last two cases. 2.The apparent dietance at small height of the arc was significantly lon- ger than that at big height in all the three conditions of presenting sti- muli. The arc with big height seemed to shrink the distance between the two end-points of a curved line. This phenomenon might be refered to as an "arc effect". These results were discussed in relation to the heuri- stics used in performing the task.

Key words: NULL