EFFECTS OF ITEM REPETITIONS AND VARIATIONS ON THE EFFICIENCY OF THE GUILTY KNOWLEDGE TEST

Two mock-crime experiments were designed to examine the effects of que stion repetition and variation on the efficiency of the guilty knowled ge test. In the first experiment, two factors (single vs. multiple que stions, and high vs. low motivation) were manipulated and in the secon d experiment, which was an analog study conducted in a police laborato ry using field equipment, only the first factor was examined. Similar detection efficiencies were obtained in both experiments when a single question was repeated 12 times, and when each of four different quest ions was repeated 3 times. The results also showed that accumulating i nformation across repetitions and across physiological measures tended to increase detection efficiency and reduce false positive errors. Th e results of Experiment 1 suggest that motivation to avoid detection m ay be associated with better detection efficiency.