Fig. 1

Shuttle maze apparatus. a Dimension of shuttle maze: the walls of the maze are 20 cm high and the entire maze is covered during the experiment with an acrylic glass. Black circles at the ends of both arms represent treat feeders. Treats are dropped from outside the wall into the feeder through a pipe. Animals pass through the short route or the long route when moving between the treat feeders. b Photographs of a prickly surfaced arch object (10 cm height × 40 cm length) and its surface, and upper view of the maze