Japanese linguists are also unlikely to know it. [自発]

A book said that most learners of Japanese, even as well as some (non-native) Japanese linguists, did not often know about one of the usages of verbs, 自発 (jihatu; spontaneous). However, the book was a little (considerably?) old; it was published in 1971. I do not know the current situation. I hope it has changed. Because 自発 is not an old usage, but a very basic one. (Every schoolchild learns it.)

Ex:
彼は正しいと思われる。(Word for word: It is thought that he is right.)
This “is thought” is a typical れる/られる that you well know. It has several meanings.

Passive voice: It is thought by me that ... = I think that.
Possibility: One can/may think that ...
Honorific: In this sentence, “he” is the object of the honor.
自発: I, without any control of humans, think that ... (I do not know how to translate it.)

To tell the truth, the core and original meaning of れる/られる is 自発. Passive, possibility and honorific derived from 自発. It is similar to or the same as “middle voice” in Greek, Latin, Sanskrit, etc.

See also:
http://lang-8.com/satoshi/journals/828534/ (田中先生は，ロシア語が分かる。 v. ロシア語を分かる。)
http://lang-8.com/satoshi/journals/993018/ (Why “あなたのコップは事故で割られました。” is wrong?)