Polygraph Glossary Practice

extrapolygraphic

Definition

Extrapolygraphic describes information not derived exclusively from the polygraph waveforms. Sources include case facts, behavioural indicators, and base rates. Some schools teach that extrapolygraphic information should inform the final decision (the clinical approach), while numerical analysis ...

What Does Extrapolygraphic Mean?

Extrapolygraphic describes information not derived from the polygraph's physiological recordings — case facts from investigators, behavioural observations, verbal admissions, background information, and all other non-waveform sources of information available to the examiner.

Carefully Bounded Role

Extrapolygraphic information is essential during the pre-test interview for developing appropriate test questions, understanding context, and assessing suitability. However, it must not influence scoring, which must be based entirely on chart data and validated methodology. This separation is fundamental to maintaining the scientific integrity of the diagnostic process.

Risk of Bias

The primary risk is examiner bias. Knowledge of case evidence might unconsciously influence scoring — even for experienced professionals. Blind chart analysis safeguards against this by having charts scored without any case information.

Standards

APA Standards of Practice require that diagnostic opinions be based on validated test data analysis, not case facts or behavioural impressions. Extrapolygraphic data may be noted in the report but must not determine classification decisions.

Cross-references

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