Othello occurs when a suspicious observer discounts cues of truthfulness. Essentially the Othello error occurs, Paul Ekman states, "when the lie catcher fails to consider that a truthful person who is under stress may appear to be lying", their non-verbal signals expressing their worry at the possibility of being disbelieved. A lie-detector or polygraph may be deceived in the same way, by misinterpreting nervous signals from a truthful person. The error is named after William Shakespeare's tragic play Othello; the dynamics between the two main characters, Othello and Desdemona, are a particularly well-known example of the error in practice.