CESTARO, V. L. and DOLLINS, A. B. A comparison of signals from two occlusive cuff cardiovascular sensors used for the psychophysiological detection of deception. July 1994, Report No. DoDPI94-R-0002. Department of Defense Polygraph Institute, Ft. McClellan, AL 36205.
This study was designed to investigate the correlation between cardiovascular signals measured during a psychophysiological detection of deception (PDD) examination using the occlusive arm and finger cuffs. Data collected during this study were used to examine the viability of the occlusive finger cuff as an alternative to the occlusive arm cuff currently used in PDD examinations. Because the finger cuff is more comfortable than the arm cuff, its use will allow examiners to ask more questions per test and facilitate development of new, longer, test question formats. Twenty subjects participated in this study. They were asked to complete a number search task (circle a specific set of two-digit numbers within a block of two-digit numbers) and participate in a PDD examination conducted by a Forensic Psychophysiologist. The PDD examination questions addressed the number circled during the number search task. Half of the subjects circled numbers within the range the questions included and half circled numbers outside of the range. Each subject completed one examination (three tests per examination). Testing conditions and question order were constant across all subjects. Dependent measures included the time-locked amplitudes of electrophysiologic signals measured from the occlusive arm and finger cuffs (i.e., amplitudes were time-locked, relative to question offset). The degree of correlation between these measures was assessed. The Pearson correlations between the right finger cuff and the left arm cuff were 0.90 or higher for 379 of 529 (72%) data pairs. The correlations between the left finger cuff and the left arm cuff were equal to or greater than 0.90 for 219 of 523 (42%) data pairs. These results, and practical considerations, suggest that the occlusive finger cuff tested (Lafayette Model 76520) is not a viable alternative to the traditional arm cuff. A finger cuff may, however, be more sensitive to peripheral blood volume changes than the arm cuff and a less problematic design should be investigated.
Key-words: cardiovascular, occlusive arm cuff, finger cuff, blood volume
This is the first study, in what will be a series of studies, to explore a variety of sensors for recording cardiovascular physiological activities (CPA). The purpose of this line of research is to find a sensor for recording CPA that will: (1) be easier to quantify; (2) be more sensitive to basic CPA; (3) not cause discomfort to the examinee; and (4) allow lengthier test formats should circumstances require them.
Other sensors to be studied are the Finapres; the Cortronic; the Impedance Cardiograph; various Systolic Time Intervals; Pulse Wave Velocity; a variety of Thumb Cuffs; the Plethysmograph; and the Cardiovascular Activity Monitor. The description and function of these other sensors will be presented in the final research reports associated with each sensor.
The results of this study suggest that the Lafayette Thumb Cuff Model 76520 is not the appropriate sensor for usage in the psychophysiological detection of deception. Other commercial thumb cuffs, as well as those developed by Institute researchers, will be studied as time and priorities permit.