Scientific Study Summary: Hasan, Y. (2017). "Violent Video Games Increase Voice Stress: An Experimental Study." Psychology of Popular Media Culture 6(1), 74-81. - NITV Federal Services | The manufacturer of the 'Computer Voice Stress Analyzer' - CVSA

In the field of law enforcement, voice stress analysis technology such as the Computer Voice Stress Analyzer (CVSA ®) is used in a range of applications, including criminal investigations, employment interviews, and immigration investigations. The CVSA detects changes in the subject’s voice which are indicative of stress. The presence of stress-induced vocal changes when correlated directly to specific questions suggests the subject is being deceptive. The validity of the technology relies on the basic assumption that external stressors, such as relevant crime-related questions, can cause detectable changes in the voice.

In 2017, a scientific study on violent video games and voice stress, published in the journal Psychology of Popular Media Culture, provided further evidence for the link between external stressors and vocal changes. Even though the study did not directly include law enforcement scenarios, it can help law enforcement professionals understand the scientific concepts underpinning the CVSA as a reliable truth verification tool for law enforcement applications.

Established Associations Between Violent Video Games and Stress

The study, “Violent Video Games Increase Voice Stress: An Experimental Study,” was conducted by Youssef Hasan at Qatar University. The goal was to use voice analysis technology to reaffirm the connection between emotional stress and playing violent video games. Before Hasan began the study, research in the field had already established that many intense video games cause stress. In particular, Hasan cites a meta-analysis review of studies, which demonstrates that playing such games induces physiological changes associated with the sympathetic nervous system. The sympathetic nervous system activates the body’s “fight or flight” response, and the scientific literature consistently shows that changes in key physiological indicators—including increased heart rate, blood pressure, and skin conduction—can all result when a player engages in a violent game.

Based on the overwhelming amount of data previously collected by researchers in the field, it was clear that playing violent video games can induce stress-related physiological effects. However, before Hasan published the paper, no researcher had specifically considered stress-induced vocal changes, so Hasan set out to fill this gap in the literature. He knew that stress can effect the natural microtremors in the vocal cords, so he created a study to measure these changes in the voices of subjects after playing violent video games.

Violent Video Game Experiment and Results

For the experiment, 87 students at a French university were randomly assigned to play either a violent video game or a nonviolent video game for 20 minutes. Afterward, they read, out loud, a story about the Kurdish Genocide—which Hasan describes as “graphic” and “distressing.” Their voices were recorded and then analyzed using a voice analysis device installed on a computer. This device identifies changes in the frequencies of the voice recordings, which in turn could be used to identify stress-related alterations in the microtremors of the vocal cords.

Ultimately, the voice stress analysis data Hasan collected verifies the connection between violent video games and stress exhibited by the voice. Hasan calculated a statistically significant increase in the level of voice stress for subjects who played violent video games, as compared to those who played nonviolent video games.

Significance for Law Enforcement Professionals

For years, the polygraph community has supported research seeking to discredit voice stress analysis technology. One claim has been that there is no real connection between stress and vocal changes, but more and more research—including Hasan’s study—disproves that assertion. There is overwhelming evidence that violent video games cause stress, and this study shows that one of the symptoms of this stress is a change impacting upon stress-related frequencies of the voice, which can be measured using voice stress analysis equipment.

Therefore, Hasan’s study provides further proof of the reliability of the CVSA for detecting stress. Even though law enforcement professionals use voice stress analysis technology in much more serious situations, the study proves the sympathetic nervous system responds to the external stress, inducing psycho-physiological effects—including vocal changes. As such, law enforcement professionals can count on voice stress analysis technology to accurately identify stress associated with deception.

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