echo question vs so/neither — match A's auxiliary (GiU Unit 51)
The frame
Section titled “The frame”A: I didn’t sleep well last night. B: Didn’t you? ✓
Echo question — repeats A’s negative polarity + past-simple did.
Two jobs for B
Section titled “Two jobs for B”| echo question | so / neither (same fact) | |
|---|---|---|
| B adds own info? | no — bounces A’s words | yes — B’s own experience |
| Polarity | same as A | matches the frame |
| Form | repeat A’s auxiliary: Didn’t you? | So + aux + I / Nor(=Neither) + aux + I |
| Intonation | rising, surprised | flat |
| Example | Didn’t you? | Nor did I |
The lock: A’s auxiliary + tense decides everything
Section titled “The lock: A’s auxiliary + tense decides everything”- A didn’t sleep (past simple) → echo Didn’t you?; same-fact Nor did I. ✗ Nor do I, ✗ Nor am I, ✗ haven’t either
- A haven’t slept (present perfect) → Haven’t you? / Nor have I / I haven’t either
- A can’t sleep (modal) → Can’t you? / Nor can I
- A was tired (be) → Were you? / So was I
- A positive → echo Did you?; same-fact So did I
Verb-type map: be → am/was; have → have; modal → can/could/will; ordinary verb → do/does/did.
Disambiguating when both fit
Section titled “Disambiguating when both fit”Does the prompt give B a shared fact? No → echo. Yes → so/neither.
In this card the choice list contained no past-simple so/neither (only Nor am I, So do I, Nor do I, So am I, So would I, Neither will I, I haven’t either — all tense-mismatched). Only the echo survives → Didn’t you?.
Source
Section titled “Source”Raymond Murphy, English Grammar in Use, Unit 51 — Auxiliary verbs / I think so. Ebot lesson 2026-09-05.