CPE Calibration 2 — Questions and Answers
Question 1: During polygraph calibration, what is the primary purpose of a 'known lie' test?
- To establish a physiological baseline for deception responses (Correct answer)
- To test the sensitivity of the pneumograph channel
- To verify that the polygraph chart paper feeds at the correct speed
- To check that the cardio cuff is inflated to the proper pressure
Correct answer: To establish a physiological baseline for deception responses
A known lie test establishes a subject-specific physiological baseline so the examiner can identify deception-related responses relative to truthful ones.
Question 2: Which galvanic skin response (GSR) value during calibration would most likely indicate a sensor placement or contact problem?
- A resistance reading of several kilohms
- A resistance reading near zero ohms (Correct answer)
- A gradual drift in baseline resistance over time
- Fluctuating resistance during a deep breath
Correct answer: A resistance reading near zero ohms
A near-zero ohm reading typically indicates a short circuit caused by bridging gel or improper electrode contact, not a valid skin conductance signal.
Question 3: When calibrating the cardiovascular component, the examiner notes the cardio tracing is flat-lined. The most likely cause is:
- The subject has an abnormally slow heart rate
- The cuff pressure is too low to detect pulse (Correct answer)
- The sensitivity setting is correctly set to zero
- The subject is in a relaxed, resting state
Correct answer: The cuff pressure is too low to detect pulse
Insufficient cuff inflation pressure prevents the transducer from detecting arterial pulsation, producing a flat cardiovascular tracing.
Question 4: A polygraph examiner observes that both pneumograph channels show identical, mirror-image tracings. This most likely indicates:
- Normal respiratory coupling between thoracic and abdominal breathing
- A wiring or channel cross-connection error in the instrument (Correct answer)
- Hyperventilation producing synchronous chest and abdominal movement
- Correct calibration of both respiratory channels
Correct answer: A wiring or channel cross-connection error in the instrument
Perfectly identical mirror-image tracings suggest a signal cross-connection or wiring fault rather than a legitimate physiological response.
Question 5: What does it mean when a polygraph instrument is described as having 'inter-channel synchronization' during calibration?
- All physiological channels record data simultaneously at the same time reference (Correct answer)
- The sensitivity of each channel is set to the same numeric value
- The pneumograph channels are averaged into a single combined tracing
- The GSR and cardio channels share one common amplifier circuit
Correct answer: All physiological channels record data simultaneously at the same time reference
Inter-channel synchronization ensures that all recorded physiological signals are time-aligned, allowing accurate comparison of responses across channels.
Question 6: During calibration of a computerized polygraph, the examiner adjusts the 'gain' setting. This adjustment controls:
- The time delay before recording begins after a stimulus
- The amplitude of the recorded physiological signal (Correct answer)
- The sampling rate at which the analog signal is digitized
- The baseline offset of the electrodermal tracing
Correct answer: The amplitude of the recorded physiological signal
Gain controls the amplification of the physiological signal, directly determining the height (amplitude) of the tracing on the chart.
Question 7: A subject's baseline electrodermal activity during calibration shows a very slow recovery rate after each stimulus. As an examiner, you should interpret this as:
- An instrument malfunction requiring immediate recalibration
- A normal physiological variation that may reflect autonomic tone (Correct answer)
- Evidence that the subject is deliberately suppressing responses
- Proof that the GSR electrodes have insufficient gel
Correct answer: A normal physiological variation that may reflect autonomic tone
Recovery rate after electrodermal arousal varies among individuals and reflects normal differences in autonomic nervous system function, not instrument error.
CPE Calibration 2
During polygraph calibration, what is the primary purpose of a 'known lie' test?