Assessing the concealed information test : countermeasures, stimuli, group and measures

The concealed information test (aka the Guilty knowledge Test) is a well-established paradigm for memory detection often advocated as a method for deception detection. Theoretically grounded, the concealed information test (CIT) exploits orienting and response inhabitation to detect concealment. The test compares responses to information that a knowledgeable suspect would recognise against equally plausible alternatives. Traditionally the CIT can be conducted using a polygraph set up measuring electrodermal activity, heart rate and respiration to compare the physiological changes found during orienting. Recent research has also found that a reaction time task CIT design can also be effective in discriminating those with and without guilty knowledge. The purpose of this work is to demonstrate the robustness of the CIT for both the physiological approach and the reaction time approach across a range of different stimuli, tasks and designs. Stimuli used are mock crime procedures, planned crimes and autobiographic scenes. Standard and Group CIT are tested and the effectiveness of countermeasures are considered. Various scoring methods are examined when combining physiological channels and also when pre-test is used to determine individual channel sensitivity. Finally the effectiveness of different overt and covert measures including standard polygraph, facial thermography, pupil dilation and voice stress of are discussed. The experiments reported will help to further demonstrate the effectiveness of various CIT designs and further advocate its use in the field