3-position scale

What Is the 3-Position Scale?

The 3-position scale is a simplified numerical scoring system used in polygraph test data analysis to evaluate physiological responses recorded during a structured polygraph examination. It functions as an abbreviated version of the more widely used 7-position scale, reducing the range of assignable values from -3 through +3 down to just -1, 0, and +1.

How the 3-Position Scale Works

The fundamental principle underlying the 3-position scale is the same as its 7-position counterpart: physiological reactions of greater magnitude are caused by stimuli that are more psychologically significant — or salient — to the examinee. When evaluating each comparison point on a polygraph chart, the examiner assigns one of three possible values:

Negative Values (-1)

A score of -1 indicates that the examinee displayed a greater physiological response to the relevant question than to the adjacent comparison question. In the context of Comparison Question Testing, consistent negative scores across multiple comparison points and chart presentations suggest the examinee may be deceptive regarding the relevant issue.

Zero (0)

A score of zero indicates that the responses to the relevant and comparison questions were essentially equal, that no meaningful difference was observed, or that the data at that point did not meet minimum standards for interpretation. A zero is effectively a neutral result for that comparison point.

Positive Values (+1)

A score of +1 indicates greater physiological responding to the comparison question than to the relevant question. Consistent positive scores suggest the examinee is more concerned about the comparison questions — the expected pattern for a truthful examinee in a CQT format.

Comparison to 7-Position Scoring

The primary trade-off between the 3-position and 7-position scales is between simplicity and granularity. The 3-position scale is faster to apply and requires fewer judgment calls from the examiner, as each comparison point receives only one of three possible values. However, the 7-position scale allows examiners to express the degree of difference between responses with greater precision — distinguishing, for example, between a slight difference (±1) and a dramatic difference (±3).

Research comparing the two systems has found both to be effective for diagnostic purposes. The 7-position scale remains the more widely used approach in professional practice, particularly in the United States federal government and among APA-trained examiners. However, the 3-position scale continues to be taught and used in certain programmes, especially where speed of analysis is valued.

Decision Rules

As with the 7-position scale, the 3-position scale requires established decision rules to translate numerical scores into categorical outcomes — Deception Indicated, No Deception Indicated, or Inconclusive. The specific cut-scores differ from those used with 7-position scoring because the reduced range produces lower absolute totals.

References

See: Capps & Ansley (1992); Harwell (2000); Krapohl (1998); Van Herk (1990).