Dropping the head and plucking invisible lint from clothing while in a conversation is a signal of contempt and disapproval. In doing so, eye contact is broken to stammer the flow of conversation. The gesture says that there are unspoken objections that are withheld either because they feel that they won’t be well received, because they are too timid to speak up, or as an effort to passively attack a figure of authority.
Any other rude gestures meant to occupy the mind in lieu of paying attention, says that a person lacks respect, integrity, or feels that they undeservedly lack control in the relationship. Body language tells us that they also set out to prove it. A person can pick their nails or remove dirt from underneath them, drum their fingers, smooth their clothing when it does not require it, or seem distracted due to any number of factors. The goal of any of these gestures is to gain the upper hand through indifference and discretely ending the conversation on their terms.