Artifact

What Is a Polygraph Artifact?

In polygraph testing, an artifact is any observable change in the physiological recording that is not caused by a genuine psychophysiological response to a test question. Artifacts are essentially "noise" in the data — they appear as physiological reactions in the chart tracings but are actually caused by external factors, physical events, medical conditions, or instrument issues rather than the examinee's psychological response to the question stimulus.

Accurate identification and handling of artifacts is one of the most important skills in polygraph chart analysis. Failure to recognise artifacts can lead to incorrect scoring and unreliable test outcomes.

Common Types of Polygraph Artifacts

Artifacts can arise from many sources during a polygraph examination:

Physical Movement Artifacts

• Coughing, sneezing, clearing the throat, or swallowing
• Yawning or sighing
• Shifting position in the chair
• Scratching, fidgeting, or involuntary muscle twitches
• Head or limb movements

Medical Artifacts

• Premature ventricular contractions (PVCs) — Extra heartbeats that appear as distinctive spikes in the cardiovascular tracing
• Hiccups or gastric disturbances
• Muscle spasms or tremors
• Chronic respiratory conditions (asthma, COPD) affecting breathing patterns

External Environmental Artifacts

• Sudden loud noises (door slamming, phone ringing, outside traffic)
• Vibrations transmitted through the floor or chair
• Temperature changes in the testing room
• Visual distractions

Instrument-Related Artifacts

• Loose or displaced sensor connections
• Cardio cuff pressure drift over time
• Electrode gel drying on EDA finger plates
• Pneumograph tube displacement

Deliberate Countermeasure Artifacts

• Physical countermeasures such as tongue biting, toe pressing, controlled breathing, or anal sphincter contraction
• These are intentional artifacts designed to manipulate test results

Why Artifact Identification Matters for Polygraph Accuracy

Accurate identification and exclusion of artifacts is critical to polygraph accuracy. If an artifact is mistakenly scored as a genuine psychophysiological response, it can lead to two types of errors:

• False positives — A movement artifact during a relevant question could be mistakenly scored as a deception response, causing a truthful examinee to be incorrectly classified as deceptive
• False negatives — A countermeasure artifact during a comparison question could artificially inflate the comparison response, masking genuine deception on relevant questions

How Examiners Identify Artifacts

Trained polygraph examiners learn to recognise artifacts through several methods:

• Multi-channel pattern analysis — Genuine psychophysiological responses typically affect specific channels in predictable ways. Artifacts like coughs or movements produce simultaneous disturbances across all channels — a distinctly different signature
• Activity sensor correlation — Modern digital instruments include motion sensors on the seat and feet. When movement is detected at the exact moment of a physiological change, the change is attributable to the movement rather than the question stimulus
• Timing analysis — Genuine psychophysiological responses follow a characteristic latency pattern (typically 1–3 seconds after the question stimulus). Artifacts often occur at irregular timing or independently of the question sequence
• Direct observation — Examiners visually monitor the examinee during testing and note any observable physical events (cough, sneeze, movement) that correspond with chart disturbances

Handling Artifacts in Scoring

When an artifact is identified at a specific question, the APA Standards of Practice provide guidelines for handling:

• The affected question-response pair may be excluded from scoring for that chart
• If artifacts are frequent or severe, the examiner may recollect additional charts to obtain clean data
• If data quality is compromised beyond recovery, the examiner may report a No Opinion (NO) result
• All artifacts and their handling must be documented in the examination report

Proper artifact documentation also supports quality control review by independent scorers or blind reviewers, ensuring transparency and accountability in the scoring process.

For more information on polygraph data quality and scoring methods, visit the Polygraph Examiner Hub or explore the research database.