Look at the illustration at the beginning.The illustration on the left shows a father making a funny face to the baby and the baby laughing.When expressing this scene in Japanese, it would be a causative sentence like (1).On the other hand, the illustration on the right depicts a boy falling down in the school hallway, and his friends laughing when they saw him. To express this situation in Japanese, the passive sentences like (2) are used.

（1）  Otoosan ga akachan o warawaseta.（The father made the baby laugh.）

（2）  Otokonoko ga tomodachi ni warawareta.（The boy was laughed at by his friends.）

Causative sentences and passive sentences are constructions that express completely different meanings to native Japanese speakers, but Japanese learners may sometimes be unable to distinguish between the two.

　　The following sentence was written by a Japanese learner whose native language is Chinese.In this sentence, a passive sentence is used when a causative sentence should be used.

    (3)  Natsuyasumi wa gakuseitachi ga ningensei o yasinatte, seikatsu o jyuujits sareru (→saseru) no ni kakasenai jiki to natte iru.

(Summer vacation has become an essential time for students to cultivate their humanity and enrich their lives.)

　　I think one of the reasons for this kind of mistake is, of course, the difficult form of the verb.When the verb becomes “(sa)seru,” it becomes the causative form, and when it becomes “(ra)reru,” it becomes the passive form.  It is possible that this learner used "rare" and "sase" incorrectly. However, it is also possible that for native Chinese speakers, causative and passive sentences are so similar that they cannot tell them apart. This is because causative sentences in Chinese are sometimes translated into passive sentences in Japanese.

    What is important here is that the major difference between causative and passive sentences in Japanese involves the intention of the subject.Let's consider again the causative and passive sentences shown at the beginning.What would the meaning be if we changed the causative sentence in (4), “akachan o warawaseta”, to the passive sentence, “akachan ni warawareta”?If you use the passive sentence, “warawareta”, it would lose the meaning that the father was intentionally trying to make her laugh.  What if we changed the passive sentence in (5), “warawareta” to the causative sentence, “warawaseta”.The interpretation is that the boy fell on purpose to make his friends laugh.

   (4) Otoosan ga omoshiroi kao o shite, akachan o warawaseta （→akachan ni warawareta）.

   (5) Otokonoko ga rooka de kokete, tomodachi ni warawareta （→tomodachi o warawaseta）.

So, which expression do you think is better to put in the underlined part of the following sentence: the causative form or the passive form?

(6) Jitensha no mae no kago kara kaban o                     yooni kabaa o

                                       {torasenai/torarenai}

tsukatta hoo ga ii desu.