At the Leipzig Zoo, the scientists hid rewards such asgrapes, banana slices or toy animals under either a hollow piece ofwood, an imitation birds 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。