Page 134 - Practical English Usage 3ed - Michael Swan, Oxford

can and could (5): with see, hear, etc 125
7 criticisms
Could can be used to criticise people for not doing things. You could ask before you borrow my car.
Could have + past participle is used for criticisms about the past. You could have told me you were getting married.
For the use of might in similar cases, see 344.
8 indirect speech
Could is used in past indirect speech, when can was used in direct speech. Can you give me a hand?- What? - I asked ifyou could give me a hand.
125 can and could (5): with see, hear, etc
1 see, hear, feel, smell, taste
When these verbs refer to perception (receiving information through the eyes, ears etc), we do not nonnally use progressive forms. To talk about seeing, hearing etc at a particular moment, we often use can see, can hear etc (especially in British English).
I can see Susan coming. (NOT I'm seeing . ..)
Can you hear somebody coming up the stairs?
What did you put in the stew? I can taste something funny. Suddenly she realised she could smell something burning.
In American English, I see/hear etc are common in this sense.
2 guess, tell
Can and could are often used with guess and with tell (meaning see, know). Can/could are not normally used with know in the sense of 'find out'
(see 313.5).
I could guess what she wanted.
You can tell he's Irish from his accent. (NOT ~l:t 62"' kn6W ...)
3 understand, follow, remember
CanIcould is often used with these verbs too. It does not always add very much to the meaning.
I can't/don't understand what she's talking about. Do/Can you follow what he's saying?
I (can) remember your grandfather.
126 can't help
If you say that you cannot/can't help doing something, you mean that you can't stop yourself, even if you don't want to do it.
She's a selfish woman, but somehow you can't help liking her. Excuse me - I couldn't help overhearing what you said.
Sorry I broke the cup - I couldn't help it.
Can't help can be followed by but + infinitive without to (see 116.3), with the same meaning as can't help .. .ing. This is common in American English.
I can't help but wonder what I should do next.
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