At the Leipzig Zoo, the scientists hid rewards such as grapes, banana slices or toy animals under either a hollow piece of wood, an imitation bird's nest or an artificial hollow rock.
At the Leipzig Zoo, the scientists hid rewards such as grapes, banana slices or toy animals under either a hollow piece of wood, an imitation bird's nest or an artificial hollow rock.
在莱比锡动物园，科学家们把如葡萄、香蕉片、动物玩具等奖品放入空木头、假鸟窝或者人造空石头里面。