Common Mistakes in English - So do I, Neither did I

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The forms 'So ... I' and 'Neither ... I' are used to agree with statements other people make. 'So ... I' states that you feel the same way about positive statements:

I love ice-cream! - So do I!

'Neither ... I' shows that you a condition in a negative statement is true for you:

Peter didn't finish the homework on time. - Neither did I.

Between 'so' or 'neither' and the subject, Insert an auxiliary verb in order to complete the statement.

So do I.
Neither have I.
So will I.
Neither am I.
etc. 

Make sure to conjugate the tense correctly based on the tense of the statement with which you are agreeing. In other words, use the same tense as in the statement with which you are agreeing, or showing similarity. 

I won't come to the party next week. - Neither will I. (use of the future with 'will')
I've lived in Portland a long time. - So Have I. (use of the present perfect with 'have')
They didn't like the show. - Neither did I. (use of the past simple with 'did')
She works in the city. - So do I. (use of the present simple with 'do')

Here's an explanation of both forms and their construction. 

So … I

So + Auxiliary Verb + Subject

Use "so ... I" in a positive sense to show that we feel the same way as another person, or have performed the same action. Change the auxiliary verb related to the original statement. The form is usually used in the first person singular, however, other forms are also possible.

He flew to Geneva last summer. - So did she. (simple past 'did' for simple past verb 'flew')
I'd love to visit Poland some day. - So would I. ('would' for the modal 'would' to express a desire)
I'm meeting a colleague tomorrow. - So am I. ('am' for the helping verb 'be' with the present continuous)

Neither … I

Neither + Auxiliary Verb + Subject

Use "neither ... I" in a negative sense to show that we feel the same way as another person, or have performed the same action. Change the auxiliary verb related to the original statement. The form is usually used in the first person singular, however, other forms are also possible.

I haven't had a promotion for a long time. - Neither have I. ('have' for the present perfect tense)
They weren't sure they had the resources to complete the job. - Neither were we. (the verb 'be' only has the past form 'was / were' and does not take a helping verb)
She won't be able to attend the conference. - Neither will I. (the future with 'will')

Do you understand the rules? Test your knowledge with this So do I / Neither did I quiz.

So do I / Neither do I Quiz

  1. I don't like classical music. - __________ I.
  2. She bought a new car last year. - __________ I.
  3. They haven't been to a museum in years. - __________ she.
  4. I'm going to take a few weeks off for vacation this summer. - __________ I.
  5. Her brother had already written the report by the time the professor requested the work. - __________ I.
  6. I can't understand what he's saying. - __________ I.
  7. I haven't had a steak in a long time. - __________ I.
  8. They've been working since early this morning. - __________ he.
  1. The computer isn't working. - __________ this one. 
  2. The students would like to take a break. - __________ we!
  3. We had been working for hours before she arrived. - ________ I!

Answers

  1. Neither do I.
  2. So did I
  3. Neither has she.
  4. So am I.
  5. So had I.
  6. Neither can I.
  7. Neither have I.
  8. So has he.
  9. Neither is this one.
  10. So would we.
  11. So had I. 

 

Using the wrong tense with 'neither...I' and 'so ... I' is not the only common mistake in English. Take a look at this most common mistakes in English page for helpful explanations and examples of some more.