When a girlfriend asks to do some chores, he would do it right away, knowing that it is the only chore she needs to have done. However, when I ask him to do something, he already knows another chore will need to be done as soon as he finishes the one I asked him to do.
I had told that story to students during a coffee break and one decided to ask the same question to her husband. And his answer was? The tone of voice!