ANS and Deception
Physiological Signs of Deception
Lying is a mental exercise, but it’s also a physical event. Even for the well-prepared and practiced liar, the body can broadcast subtle signs of emotion and psychological stress. The autonomic nervous system (ANS), our body’s internal regulator, governs involuntary processes like breathing, heart rate, and sweating. While we can choose our words, controlling these physiological responses is far more difficult.
How the ANS Reacts to Emotion
My research has shown that people often lie about their feelings and that the act of lying can also trigger a range of emotions. When emotions are aroused—whether by fear, guilt, anger, or excitement—the ANS springs into action. Rapid breathing, a heaving chest, swallowing, sweating, and even a dry mouth are all potential signs of emotional arousal. These responses are largely automatic and hard to inhibit, making them reliable markers of emotional intensity.
Psychologists have debated for decades over the extent to which each emotion is linked to a unique pattern of ANS changes. Most agree that the ANS signals the intensity of emotion and some also argue that it indicates the type of emotion as well. In my studies, I found evidence that voluntarily producing emotional facial expressions can also produce emotion-specific patterns of autonomic activity.
What Polygraphs Measure—and What You Can See Without One
As I’ve pointed out elsewhere, polygraph tests are not reliable lie detection tools. This is because they detect signs of emotion, not lies per se. The polygraph measures ANS responses like breathing rate, skin conductance (sweating), and blood pressure to detect deception. The underlying assumption is that lying is stressful and that this stress will manifest as measurable changes in these systems.
Interestingly, many of these physiological responses are visible without a polygraph. A person feeling distress, guilt, or fear while lying may show:
- Rapid breathing or a heaving chest
- Frequent swallowing
- Visible sweating or even a noticeable odor
Faking and Misleading Signs
Although some autonomic physiological changes are hard to hide, others can be intentionally falsified. For instance:
- Breathing and swallowing: It’s relatively easy to mimic faster breathing or frequent swallowing, potentially creating the appearance of emotional arousal.
- Sweating: In contrast, sweating is difficult to fake or suppress, making it a more reliable marker of autonomic arousal.
Still, even real signs of arousal—whether natural or faked—don’t necessarily confirm deception. Nervousness, fear of being accused, or other unrelated emotions can cause similar reactions, leading to false positives. This is one of the reasons polygraph tests are controversial and often inadmissible as evidence.
The Future of Emotion and Deception Detection
The autonomic nervous system offers a fascinating window into human emotion, but its signals remain more of a general alarm than a precise language. Changes in breathing, sweating, and swallowing are potential indicators of emotional intensity, but pinpointing the specific emotion and meaning of these signs requires further investigation and consideration of context.
Advances in neuroscience and deception detection technologies may one day allow us to more accurately and precisely map patterns of ANS activity to specific emotions and lies. For now, we know this much: our body speaks volumes when we lie, whether through a dry mouth, a sheen of sweat, or a racing heart. And while deception may begin in the mind, the truth often lies in the physiology.
