Does the phrase "I don't think" imply that the speaker does not use his brain? Or should it not be taken literally?
Hello, Guest,
Taken as it stands, "I don't think." (full stop) it may mean that the speaker doesn't use his/her brain as you say, or that s/he acts on implusion.
However, it's mostly used as follows:
1. A: "Do you think it is going to rain?" - B: "I don't think so" (my opinion is that it is not going to rain)
2. "I don't think he's going to win the race" (my opinion is that he won't win ...)
'I don't think!' can also be a sarcastic retort.

'I see that our boss has given himself an 'excellent' rating for 'people management skills' in his annual assessment'

'Yeah, I don't think!'

(Meaning I think that he is terrible at people management skills).

Has to be done in a certain tone of voice though...
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Dear Guest,

Think about it:
"I think, so I am"

Best regards,
 nona the brit's reply was promoted to an answer.
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