Spontaneity is a cool usage of the endings ～られる and ～れる. The grammar resembles the passive, but they are semantically different. There are also unique spontaneity verbs. We'll touch on how spontaneity relates to potential phrases.
～られる and ～れる may show spontaneous action or situation. A spontaneous action or situation is one that occurs without the intention of the subject which is often one’s self. There is no will involved. This ending is typically restricted to verbs of thought, cognition, and or feeling. If mentioned, the experiencer is marked by に. The object is marked by が just like with passivization.
The presence of (the) people (there) was felt.
The course was considered.
I found myself surprised by the sound of the waves.
I found myself remembering about the old days all of a sudden.
I felt ardor.
The air came to be delicious.
To get concerned about the condition of one's hospitalized grandmother.
To find oneself sensing (the coming of) autumn.
No matter what, all I think of is that.
It seemed really mysterious.
聞こえる & 見える
The verbs 聞こえる, 見える, as well as other similar looking verbs such as 燃える and 消える also express 自発. So, we'll call these verbs 自発動詞. 聞こえる and 見える predate the potential forms 聞ける and 見られる, and because they don't actually show potential, though potential phrases do ultimately derive from spontaneity phrases due to the fact that having the potential to do something is a characteristic of you that you cannot control, we did not discuss them in the potential lesson.
So, if 聞こえる and 見える do not mean 聞ける and 見られる respectively, we need to see how they differ. Essentially, they show inherent ability whereas 聞ける and 見られる show that you can (if you want), indicating one's intentions can be realized.
聞こえる describes a naturally hearing sensation. It can be defined as "to be able to hear", "to sound", "to be audible", and even "to be famous". 見える may mean "to be able to see". It can also mean "to come into view/to appear". With ように, 見える may show what something looks like. It may also be a very respectful form of the verb 来る.
I could hear their voices even in the middle of the rain.
He looks like he's excited.
Do you think that fish can hear?
I can't hear his lecture.
To look one's age.
You can now see Kurosawa's movies in the theater.
You can hear the weather forecast on your iPhone.
I could see Mt. Kaguyama yesterday, but I can't see it today.
It appears that it's going to rain.
I can hear the neighbor's television('s sound).
I see so much better when I wear my new glasses.
He can't see very well with his right eye.
Literally: As for him, his right eye can't see very well.
Historical Note: Long ago ～ゆ was used just like ～られる and ～れる and remains part of many verbs like 燃える and 消える. So, these example verbs come from 燃ゆ and 消ゆ. You may even see these old forms purposely used in songs and poetry. Their roots still end in "y" and they're intransitive and spontaneous in nature.
Bridging Contexts between Spontaneity and Potential
Another verb to note is 思える. It can show spontaneous thought. It can also show the ability of thought which can be seen as coming from 思ゆ or 思われる. 思える and 思われる are almost identical, but the only true difference between the two is that the former is felt to be more objective and the latter is felt to be more subjective.
Before going to examples, note the mentioning of "potential". There are clear instances in which verbs can be interpreted as both a 自発動詞 and a 可能動詞. However, the use of a speech modal such ～てしまう or ～てくる are very important to get both meanings.
Student A managed to be able to write it before I knew it.
24. びっくりするくらい泣けてきたわ。 (Feminine)
I was surprised at how many tears (I was able to) shed.
Try making a movie one would naturally laugh to.
I cannot/could not think of it as a good work.
The place name's origin is thought to come from Ainu.