What indicators does a sentence use when speaking of myself or another?
I've gone through a bunch of the lessons up to Clothes & Hobby 2. I often find myself struggling to tell if the sense is speaking about myself or someone else. Are there generally any clues in a sentence that would say (for example) "I bought that," versus "(He/She) bought that?"
Obviously, when the question has the word bubbles laid out for you, it's easier to tell. When the word bubble translation comes up, I generally don't see the indicator yet. Although, when you have to translate and type the sentence out. Most of the time, it's not clear to me who the subject is, myself or another.
With Japanese, a sentence can be grammatically correct without actually specifying the subject. So for instance, かばんをかいました is indicating that a bag was the object being bought, but doesn't say who. In a normal Japanese conversation, who bought it would be clear from the context. "I bought a bag," "he bought a bag," and "she bought a bag" all need to be acceptable translations for that sentence.
Spoken Japanese relies heavily on the context of what going on around the conversation, so a speaker doesn't always include the subject when it would be understood. The speaker would say わたしはかばんをかいました or (specific person)はかばんをかいました in a case where it either wouldn't be picked up from context, or there is a need to emphasize who did it. If someone walks out of a store with a new bag and says かばんをかいました then it's clear that the speaker is the one who bought it, and there is no need to include わたしは.
In short, there's often nothing in the actual sentence to specify it. That's one of the problems when working with out of context sentences, unfortunately.
Isn't it actually even more far-reaching that that? Judging from my studies so far, the default case in Japanese seems to be to omit the subject and the topic. You only specify either if there's a reason for it, for example if you want to emphasize the subject or if want to switch the conversation to a different topic.
I've done about 40% of the tree. Normally when you have to write a translation in English, the course is pretty good about accepting whichever subject pronoun you feel like. There are some exceptions. I don't have the Japanese background to understand if there is a reason for them or if they are just beta-phase omissions. Specific cases I recall were sentences about having an older brother or sister. I tried "we" and "they" without success although "I," "he," and "she" worked.
Mainly speaking, the Japanese language likes to omit their subjects. Most of the time, if the subject is omitted, it is safe to say you are either speaking about yourself or about the person you are talking to.
Here are some examples, subjects will be in brackets:
(あなたは)もう食べましたか？(Anata wa) mou tabemashita ka? "Did you eat already?"
(私は）まだ食べませんでした。 (Watashi wa) mada tabemasen deshita. "No, I didn't eat yet."
(私は）友達と映画を見に行くのが好きです。 (Watashi wa) eiga wo mi ni iku no ga, suki desu. "I like going to watch movies with a friend."
If there is no question being asked and there is no subject particle (indicator), it is assumed that you would be talking about yourself:
（私は）アニメが好きです。 (Watashi wa) anime ga suki desu. "I like anime."
If there is a question being asked and there is no subject particle (indicator), then it is assumed that you are talking about the person you are speaking to.
(あなたは）アニメが好きですか。 (Anata wa) anime ga suki desu ka? "Do you like anime?"
And if clarification is needed, they would add the subject back into the conversation:
A: 明日はパーティー来ますか？Ashita wa kimasu ka? "Are you coming to the party tomorrow?" B: いいえ、行きません。友達は行きます。Iie, ikimasen. Tomodachi wa ikimasu. "No, I'm not going. A friend is going."
I hope this helps.