Use of を with seemingly intransitive verbs describing emotions

Question

何を悩んでいるの
What is troubling you?

何をそんなに興奮しているんだ
What are you so excited about?

I keep seeing sentences like the above where verbs, which seem to me to be intransitive, are taking 何 as an object. Are these examples of a larger class of cases where this happens? Can someone please explain what is going on with the grammar here?

I feel that this question must be related but I doubt there is any accusatory tone in the examples I am looking at.

Answer 1

As pointed out in the comment section, the first sentence is a plain transitive usage of 悩む.

For the second sentence, I do feel an accusatory overtone similar to that in 何をにやついているんだ explained in the linked question:

• 何にそんなに興奮しているんだ → The speaker doesn't feel good or bad about that fact that the listener is excited, but he is simply curious why the listener is excited.
• 何をそんなに興奮しているんだ → The speaker is dubious and/or annoyed, and he thinks there is nothing the listener should be excited about.

Both of these would be translated into English as "What are you so excited about?", but they are slightly different in Japanese, and the 何を version is closer to a rhetorical question. (The difference is not huge. The former can sound accusatory depending on the context.)

Answer 2

を can indicate the cause of some human emotion, as in:

メリーは父の死を悲しんだ

"Mary was saddened by her father's death"

Or:

私は浩の大学入学を喜んだ

"I was happy about Hiroshi's entering college"

Note that yes, these verbs are still intransitive.

Answer 3

They're probably bitransitive verbs. You can say, for example:

学校を休みました。(transitive)
家に休みました。(intransitive)

It happens in english too.

She is eating (intransitive)
She is eating the cake (transitive)