Procedure used by many PDD examiners before or between the regular tests. One of its purposes is to demonstrate to examinees that the polygraph works with them, and in doing so, reassure the innocent while heightening the guilty person’s concern about the relevant questions. Other purposes include allowing the testing examiner set the gains properly, to verify that the sensors are properly placed and functioning correctly, and to acquaint the examinee with the examination procedures. Virtually all stimulation tests use a question set of very similar items in which is embedded a single item that the subject is directed to lie about. There are several types of stimulation tests. The more common are the card test, known numbers acquaintance test, blind numbers test, control test, and true blue control test. Tests of this nature were used by early polygraph examiners for the purpose of comparing the reactions on the stimulation test with those from the relevant questions on the R/I test. Stimulation tests were sometimes referred to in general as stim tests.