a lie. More recently, scientists have attempted to establish the differences between truthful and deceptive behavior using a myriad of psychological and physiological approaches. In 1969, Ekman and Friesen used straightforward observation methods to determine deceptive non-verbal leakage cues, while more recently Rosenfeldet et al. used magnetic resonance imaging (MRI) to detect differences between honest and deceptive responses.

In 1989, DePaulo and Kirkendol developed the Motivation Impairment Effect