Differential effects of practice on the executive processes used for truthful and deceptive responses: an...

Behavior and event-related potentials (ERP) were recorded while participants made truthful and deceptive responses about previously memorized words under three instructional conditions: consistent truthful, consistent deceptive, and random deceptive. To determine if practice affected the deception-related activity we reported previously [R. Johnson, Jr., J. Barnhardt, J. Zhu, The deceptive response: effects of response conflict and strategic monitoring on the late positive component and episodic memory-related brain activity. Biol. Psychol., 64 (2003) 217-253; R. Johnson, Jr., J. Barnhardt, J. Zhu, The contribution of executive processes to deceptive responding. Neuropsychologia, 42 (2004) 878-901], participants performed two blocks of 145 trials of each condition. In the consistent truthful condition, practice benefited performance as indicated by decreased reaction time (RT) and RT variability. In addition, practice increased P300 amplitude and decreased the amplitude of a medial frontal negativity (MFN), which is believed to index the use of response-monitoring processes. However, a different pattern of results obtained in the two deception conditions. Although practice decreased RTs by almost as much as in the consistent truthful condition, the extent to which deceptive response in both conditions were slower than those in the consistent truthful condition actually increased slightly. Hence, the component of RT reflecting processing of conflicting response information did not decrease. In accord with the RT results, MFN amplitudes in the consistent deceptive and random deceptive conditions were unaffected by practice, suggesting that the amount of executive processes required to make and/or monitor deceptive responses was undiminished by practice. Although P300 amplitude increased slightly in the consistent deceptive condition, there was no change in the random deceptive condition. Thus, a major finding here is that, unlike truthful responses, the conceptually driven response conflicts underlying deceptive responses appear to be as resistant to practice-induced changes as described previously for perceptually driven response conflicts.