There are a lot of sources for error here. 1. You may pay more attention to ads you wouldn't have noticed. 2. Something prompted you to say what you said and Fa

There are a lot of sources for error here. 1. You may pay more attention to ads you wouldn't have noticed. 2. Something prompted you to say what you said and Facebook may be aware of that cause. 3. Your behavior may change as a result of having said it and Facebook may pick up on that. There is a solution to all this. A (repeated) double blind experiment. Pick two phrases. Say one so the phone can hear and one so it can't. It's very important you don't know which is which. You could eg have a friend put the phone in one of two rooms.