Abstract
Short-term memory capacity called the magical number, lasts 5-60 seconds and is about 7±2 (2.8bits) irrespective of sensory modality.
We showed that the magical number 7±2 exists in the recent memory of a strange route which is a long-term memory, and maintained it from 10-60 minutes. The first experiment in which subjects must grasp a topological structure of a strange route, was done for six routes, consisting of seven to fourteen turns. The results showed that the limit is about eight turns. The second experiment in which subjects must rearrange sections obtained by dividing a route in a fixed interval and by arranging at random, was done for the five, seven, ten and twelve divided sections. The results showed that the rearrangement limit is between seven and ten sections. Then the shape of a map drawn when the topological structure was not grasped was compared with that when it was grasped through a quantity of straight line degree which was newly introduced in this paper. When the topological structure of route was not grasped, the frequency of the straight line degree showed a bias of about 1 or 1/2, but did not show this when it was grasped.
