Social interaction is the mutual influence between two or more individuals. It often occurs through signals and sometimes symbols, at least in humans. The sharing of meaning and an evolutionary advantage for all sides make interplay a communicative act. Individuals use a language when codes (i.e., sets of signs) share (even partially) senses, connections (between elements), or contexts. There are at least three general misconceptions in this field: the overestimation of nonverbal cues, some Palo Alto Group principles, and the assumption that people always use body movements as a language. These misconceptions often do not produce the desired results, as the story of the Screening of Passengers by Observation Techniques (SPOT) program suggests.