When we have a momentary rise in our anxiety level, in an extremely high percentage of the time portions of our head and/or neck will itch. This is not imaginary - they truly itch. There are probably several reasons for this that have not to date, been fully elicited - however one of these is a simple rise in blood pressure. The blood vessels will press on surrounding tissue - which of course contains nerve endings and this pressure leads to pruritus. When a lie is told (or heard) we tend to experience this itching/swelling in some areas more than others. The nose is particularly prone to this phenomenon. Another region is just above the lip and below the nose - in the "mustache area". So when we tell a lie, we scratch the nose and above the upper lip particularly often. Part of this particular gesture is "vestigial behavior" from childhood - when the mouth is immediately covered once a lie is told. We partially, but never completely "unlearn" this response as we grow older. Here, the lovely Megan Fox is shown in this highly characteristic Body Language maneuver.