Fig. 1. Experimental arrangement. Only one half (180°) of the cage is represented. At the centre of the arena base, a small hole (5 cm in diameter) allowed a 60 cm long and 1 cm thick wood stick to project from a platform situated 15 cm below the base of the cage. The stimuli were presented by a loudspeaker positioned 60 cm away from the centre of the arena and 90 cm from the ground.