I also don’t know.

In Singapore, the answer to a question will often be “I also don’t know.” The implication is that the asker doesn’t know and that the answerer is thus the second person who doesn’t know.

We Americans don’t say ‘also’ in English when we don’t know unless at least one person has already failed to answer the question.

In Singapore:

“Where can I get some good Italian food?” asked Amelia.
“I also don’t know,” said Bob.

In the US:

“Where can I get some good Italian food?” asked Amelia.
“I don’t know,” said Bob.
“I also don’t know,” said Cindy.

Cindy is the second person to say the phrase “I don’t know.” The word ‘also’ is just there to emphasize the echo. But probably Cindy wouldn’t even use ‘also’. She’d probably say “me neither” or “I don’t know either.”