I'm thining about my first experience at Belfast Airport. In the check-in counter, the beautiful clerk, prepared to check in my suitcase, asked me: 
    "Is this suitcase packed by yourself?" 
    "Yes", I replied. 
    "Has anyone else touched the inside of your suitcase?"
    "I don't think so", was my reply.
My friend exchanged a few pleasant lines with the clerk, and my suitcase was checked in. 
My friend later told me that when asked "Has anyone else touched the suitcase", I should have replied in a firm tone, "No." This is to show I'm sure that there is nothing illegal in the suitcase. Otherwise, the clerk may request to check the inside of my suitcase. 
This is a case in point to show that culture does play an important role in Second Language Acquisition.