
Students find responses with "So" and "Neither" difficult to understand. I can see why. They are confusing for a non-native speaker.
There are 4 different situations in this type of response.
- Agree to a positive statement eg. I love walking in the mountains. So do I.
- Disagree with a positive statement eg. I didn't like that movie. Actually, I did.
- Agree with a negative statement eg. I can't stand rude people. Neither can I.
- Disagree with a negative statement eg. I've decided I'm not going to India. Oh, I am.
Notice that whether you agree or disagree we don't use "not". We also must use the form of the verb used in the first statement. That could be a different tense or using a modal.
Remember that it's the question form we are using: "do, did, can and am".
When agreeing we use "so" or "neither", positive or negative, and when disagreeing we can use "oh" or "actually".
So, it's quite easy really.