Penile circumference changes were measured using an indium gallium gauge supplied by Behavioral Technology, Inc. The signal from the indium gallium gauge was amplified by 1000; data retrieval was set at a rate of 10 samples per second. Each penile gauge was calibrated to a full range of 3.0 cm before each assessment to ensure that the correlation between circumference and deflection was linear. GSR electrodes and respiration belts were also used for deterrence and potential detection of faking or suppression attempts.