After a period of time,the operation of the lever was taken over by a mechanical arm and each rat quickly learnt that the mere thought of using its limbs to operate the lever stifi resulted in access to the food.

• 一段时间以后，杠杆操作被机械手臂代替，每只老鼠很快就明白了只要有用四肢操作杠杆的想法依然可以取到食物。