“This isn’t a good movie.” “I think so.” Does “I think so” here mean I disagree and think it is a good movie? Thanks.

If you are looking to agree, "I think so too" would be correct here. If you are looking to disagree, "I don't think it is" would be correct here.

"I think so" is a confusing response, honestly - if someone said that to me in this context, I wouldn't know whether they were agreeing or not. "I think not" is a somewhat old-fashioned phrasing (at least to me as an Australian) so you'd be unlikely to hear it in a context like this, but it would be clear that the person agrees the movie was bad. "I don't think so" sounds natural and fine to me, and is probably what I would say if someone said "This isn't a good movie" and I agreed with them, though I would probably preface it with "no" i.e. "No, I don't think so".

Responding to negative statements can be a bit wiggly in english. I agree with the poster who says "I think so too" or "I agree"

Neither responses are correct or natural, nor do they make sense.

It could mean either way, so it would be a bad idea to say. It would be better to say "I agree" or "I disagree", or else to be even more specific, for example "I thought it was all right", or, "I didn't like it, either" .

"I think so too" would have been more clear. But I would say, "I agree".

To disagree you would say “I think it is”

If that's how to conversation happened. It seems like you disagree with the speaker and the movie was good. You should just say "Yeah" or "he/she's made better movie". A. This isn't a good movie B. I don't think so (you disagree with the speaker). I think not (you disagree speaker). C(agreeing with the speaker): Yeah I agree. Yep.

I would say something more obvious… “I agree” or “I disagree”

Native speaker here that disagrees with some of the others - I’d use this phrase, with emphasis on *I* think so, meaning I disagree, and think it is a good movie

If you stress the "I" then yes, it'd mean that you disagree and you think it's good. If you don't stress it then it would sound confusing to me.

This is ambiguous and you would respond with more clarity. None of your answers are clear. If you like the movie you’d say yeah it is. If you don’t like the movie you’d say no, it’s not.

Too ambiguous to tell

It’s not clear. When responding to an opinion like that it’s more clear to say whether you agree explicitly. “I agree”

I would ask the person this same question. It's a common issue in English with negative questions, or responses to negative statements. "Did you not go to the party?" "No." "...No, you did not go or no, you didn't not go, as in, you went?" Happens all the time, and if people tell you there's rules, don't assume whoever you're talking to knows them, because it might vary wildly from person to person. In this particular case you posted, a lot could revolve around tone. I don't know how to describe the change in pitch but people will sound different, fairly consistently, if they are arguing/disagreeing with your statement compared to when they agree.

"I think it is" is more natural, and it would be about the movie being good. When saying it, we'd put emphasis on the "I", to show that my opinion contrasts yours so they are not the same "I think so", would usually only be for responding to a question

None of your three responses really work. "I think so" (at least in American English) is used in response to a question like "Is this a good movie?" or "Are they coming at 6:00?" The other two are negative responses to questions, rather than responses to statements.

i don't think most native speakers would say "i think so" in response to a negative statement, or know how to interpret such a statement.

”this isn’t a good movie“ ”really? I think it is.“

If I said "This isn't a good movie" and you responded "I think so," then I would think you probably misheard what I said. If you responded "I don't think so," if you emphasized the "I" then I would interpret it as meaning that you disagree and you think it is a good movie. But if you said it with the typical prosody, where "I" isn't particularly emphasized, then I would think you misheard what I said. If you responded "I think not," I guess I might interpret it as you agreeing with me, but it would be a weird way of agreeing. That's not really a normal thing to say in that context. Again I would probably at least wonder if you misheard what I said.

-I think this is a good movie -This isn’t a good movie. -Well, I think so. This forum is so xenophobic 😭 I’m telling you when they are in this state of mind they struggle to make sense of varying contexts and intonations. They don’t really know grammar; they know who sounds American. There’s no way none of the responses make sense to you. All of them would slip by in conversation like nothing! Other Western European languages have clearer answers for saying something positive in contradiction. That’s something I realized studying Spanish and French. Alternatively, this may be this conversation as well: -This isn’t a good movie. -I think so as well. The casting was horrible!