automatic mode

What Is Automatic Mode?

Automatic mode refers to a feature on computerised polygraph instruments that automatically adjusts sensor gain settings, centering, and display parameters without manual intervention from the examiner. In automatic mode, the instrument's software continuously monitors the incoming physiological signals and makes real-time adjustments to keep the tracings properly centred and appropriately scaled on the screen, compensating for gradual baseline drifts and sudden signal changes.

How Automatic Mode Operates

Modern digital polygraph instruments continuously digitise the raw physiological signals from the electrodermal, pneumograph, and cardiograph sensors. In automatic mode, the software applies algorithms that detect when a tracing is drifting off-centre, when gain settings produce tracings that are too large or too small for optimal evaluation, or when baseline shifts require recalibration. The instrument then adjusts these parameters transparently, maintaining readable tracings throughout the examination.

Automatic vs. Manual Mode

The alternative to automatic mode is manual mode, where the examiner controls all gain, centering, and sensitivity adjustments manually. Each approach has advantages:

• Automatic mode — Allows the examiner to focus on the examinee and the test protocol rather than instrument adjustments. Particularly useful during the pre-test phase and for less experienced examiners. May occasionally make adjustments at inopportune times (such as during a response window)
• Manual mode — Gives the examiner complete control over when and how adjustments occur. Preferred by many experienced examiners during actual chart collection because it ensures no automatic adjustment occurs during a scoring window that might alter the appearance of a response

Impact on Data Quality

The choice between automatic and manual mode does not affect the underlying raw data being collected — both modes digitise the same physiological signals. The difference lies in display parameters. However, some examiners prefer manual mode during chart collection because automatic gain changes could theoretically cause a quality control reviewer to misinterpret a sudden gain change as a physiological response, or vice versa. Most instrument manufacturers recommend that examiners develop proficiency with both modes and select the appropriate mode based on the testing phase and circumstances.

Modern Implementation

Current polygraph software from manufacturers such as Lafayette, Limestone Technologies, and Stoelting typically offers both automatic and manual modes with easy switching during a session. Some systems provide a hybrid approach where automatic centering is active but gain adjustments require manual confirmation.