Effects of questions' repetition and variation on the efficiency of the guilty knowledge test: a reexamination.

The effect of question repetition and variation on the efficiency of the Guilty Knowledge Test (GKT), based on electrodermal and respiration measures, was examined in a between-subjects experiment with 3 conditions. Each participant was presented with a sequence of 12 biographical questions. In Condition 1, a single question was repeated 12 times; in Condition 4, each of 4 different questions was repeated 3 times; and in Condition 12, 12 different questions were used. A monotonic relationship between the number of different questions used and detection efficiency was observed only with the electrodermal measure (the areas under the receiver operating characteristic curves, obtained with this measure in Conditions 1, 4, and 12 were .68, .81, and .99, respectively). These results demonstrate that a GKT based on multiple questions is superior to the use of many repetitions of a single or a few questions, and it can reach an almost perfect detection efficiency.