Auxiliary verbs - so / neither
so + auxiliary + subject
neither (or nor) + auxiliary + subject
We can use so / neither / nor + auxiliary to show that people have something in common (i.e something is the same about them)
This can be in the form of a short answer:
S1: I feel tired.
S2: So do I.
Or in a statement comparing people.
Tim wants to go and so do Simon and Janet.
It doesn't make any difference. They're the same.
Pronunciation of 'neither'
The first syllable 'nei' can be pronounced in two ways:
'nei' - rhymes with 'eye' This is more common in British English
'nei' - rhymes with 'see' This is more common in American English
How to respond when you do not have something in common
We only say 'So / Neither / Nor + aux + I' when we have something in common with the first speaker:
S1: I like this cheesecake.
S2: So do I!
However, sometimes we want to make it clear that we are different.
S1: I've never seen a shark before.
S2: Oh, I have. We saw some in the zoo last year.
In this case, S2 has given a short answer with an auxiliary ('I have') and a short explanation.
S1: I don't like this music.
S2: Really? I do. Michael Jackson's one of my favourites.