inspiration/expiration ratio

What Is the I/E Ratio?

The inspiration/expiration (I/E) ratio compares inhalation duration to exhalation duration. Normally about 1:2 at rest, it was first reported by Benussi (1914) to change during deception. However, more recent research has not found it to be of strong diagnostic value in manual scoring, and Benussi's original approach differs considerably from what is sometimes taught in polygraph schools.

Professional Standards

The American Polygraph Association Standards of Practice govern the use of polygraph techniques and scoring methods. Only validated techniques with published peer-reviewed research support should be used for diagnostic purposes. The test data analysis method must be approved and applied consistently to ensure reliable and defensible results.

Research Basis

For access to the published research supporting polygraph techniques and scoring methods, visit the polygraph research database. Understanding the empirical foundation of each technique is essential for practitioners, researchers, and those evaluating polygraph evidence.

Professional Context

This concept forms part of the knowledge base expected of qualified forensic psychophysiologists. Training at APA-accredited schools covers the theoretical foundations, practical applications, and research evidence underlying all aspects of polygraph methodology. Ongoing continuing education ensures practitioners stay current with developments in the field.