Psychologist (d. 2006) and ardent critic of the CQT. Dr. Lykken produced numerous writings for the scientific and general press, including a book, A Tremor in the Blood, in which he argued strongly that the CQT is fatally flawed, that it resulted in wrongful criminal convictions, and it was vulnerable to countermeasures by the guilty. Dr. Lykken did not publish any research of his own on the CQT but used anecdotal histories and interpretations of other research to form his arguments. Lykken endorsed the Guilty Knowledge Test (GKT, now known as the Concealed Information Test, or CIT), an alternate PDD testing format. The CIT has not been widely used outside of Japan. See: Lykken (1998).