Polygraph Instrument or Polygraph Machine?
This article is a response to Director Raymond Nelson’s piece in the Sept/Oct APA Magazine. First, I want to take a moment to commend Ray for his thoughtful contributions to the APA and the polygraph profession as a whole. His work consistently reflects a deep dedication to advancing our field and fostering meaningful dialogue. That said, I’d like to offer my perspective on the ongoing debate surrounding the terms “instrument” versus “machine” within the polygraph community. While this distinction may seem trivial or even semantic at first glance, it holds great significance in how we present ourselves and communicate with the broader scientific and professional communities.
As Ray pointed out, the term “instrument” is widely taught and used in polygraph schools. During my decade teaching neurophysiology at NCCA from January 1997 to January 2007, I made it a point to emphasize that the recordings obtained during a polygraph examination are captured by an “instrument,” not a “machine.” This distinction is more than just a matter of word choice—it reflects the nuanced and specialized role of the polygraph device in our work and highlights the scientific precision involved in its operation.
Understanding “Instrument” vs. “Machine”
To fully appreciate the significance of this debate, it’s helpful to consider how the terms “instrument” and “machine” are understood in various fields. These words carry different connotations and are associated with distinct functions. For clarity, let’s start with some common definitions of the term “instrument,” as provided by Joel Reicherter, Professor Emeritus at SUNY:
- Musical instruments: Devices designed to produce music.
- Legal instruments: Documents that serve specific legal functions.
- Surgical or dental instruments: Tools crafted for precise procedures in medical or dental settings.
- Specialized tools: Instruments designed for specific professional uses.
- Medical instruments: Devices like EKGs or EEGs that collect physiological data for diagnostic purposes.
Across all these examples, an instrument is defined as a tool designed for precision, data collection, or a very specific purpose. It is not necessarily associated with performing physical tasks; instead, it aids in observation, analysis, and decision-making.
By comparison, a “machine” is typically thought of as a device that performs mechanical work. Machines are task-oriented devices that convert energy into force to accomplish a specific goal. For instance:
- A snowblower converts electricity or fuel into air pressure to move snow.
- A lawnmower transforms gasoline into the motion of rotating blades to cut grass.
- A bulldozer uses fuel to generate power that moves soil.
Machines perform mechanical tasks by converting energy into motion or force—tangible outputs that directly impact the physical world.
The Polygraph: Instrument or Machine?
To decide whether the polygraph is better described as an instrument or a machine, we must ask: What “work” does it perform? A machine, as defined above, performs mechanical work, such as moving objects or generating force. The polygraph, however, does not engage in such tasks. Instead, its primary function is to collect neurophysiological data, such as electrodermal activity, cardiovascular responses, and respiratory patterns, which are related to a subject’s psychological and physiological reactions during questioning. The data collected by the polygraph is then carefully analyzed by an examiner to assess the subject’s truthfulness.
In this sense, the polygraph parallels medical instruments like the EKG or EEG, which are used to record and display physiological data for analysis by a trained professional. Much like these devices, the polygraph is a tool for data acquisition, not a machine that performs physical tasks. The ultimate responsibility for interpreting the recorded data rests with the examiner, whose expertise ensures the process is carried out accurately and ethically. This further supports the argument that the polygraph is best described as an instrument—a device designed for precision and analysis—rather than a machine.
Scientific Considerations and Error Rates
It is also important to remember that no scientific test is entirely free of error. When we describe a test as “scientific,” we mean it follows established protocols and procedures, not that it is infallible. A critical part of any scientific test is the use of controls to ensure accuracy. In the context of polygraphy, “inconclusive” results serve as a safeguard, helping to minimize error rates and maintain the integrity of the process.
The polygraph device must meet rigorous scientific standards in order to accurately record neurophysiological responses during questioning. However, it is the examiner, as the decision-maker, who interprets the data using validated methods, pretest interviews, and post-examination analysis. This distinction underscores the polygraph’s function as an instrument that assists in scientific evaluation rather than a machine that mechanically carries out a predetermined task.
The Importance of Precise Terminology
Why does this distinction matter? The way we describe our tools and processes reflects the professionalism and scientific rigor of our field. Using precise terminology helps us present polygraphy as a legitimate and reliable discipline to the broader scientific community and the public. Referring to the polygraph as an instrument emphasizes its role as a specialized tool for data collection and analysis, aligning it with other respected scientific and medical devices.
A Proposed Compromise
If the debate over terminology continues, perhaps a compromise is in order. One potential solution is to adopt a more neutral term, such as “polygraph device.” This phrase acknowledges the polygraph’s function as a tool for scientific data collection while avoiding the semantic challenges associated with “instrument” versus “machine.” It also underscores the polygraph’s versatility and its role in supporting the examiner’s expertise.
Conclusion
In conclusion, the polygraph is best described as an instrument—a device specifically designed to record and present neurophysiological data for expert analysis. While machines perform mechanical tasks by converting energy into force, instruments like the polygraph provide critical data that requires human interpretation. By using precise and thoughtful terminology, we can better represent our profession, foster greater understanding, and strengthen our credibility within the scientific community and beyond.
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