What is a common physiological symptom of deception that may be observed in a subject?

The observation of excessive sweating as a common physiological symptom of deception aligns with research on the body’s response to stress and anxiety. When individuals are being deceptive or are in high-stress situations, their bodies may trigger a "fight or flight" response. This can lead to the activation of sweat glands, resulting in increased perspiration.

Excessive sweating is often referred to as hyperhidrosis and can be a real giveaway during interrogations or interviews. It may indicate nervousness and discomfort, which are common reactions when someone is trying to hide the truth.

The other options do not typically correlate with deception. A calm demeanor may suggest relaxation or honesty, making it less likely to be a signal of deception. Increased blood circulation, while it occurs physiologically in response to various factors, is not distinctly tied to deceit. Steady breathing is often a sign of calmness and control rather than deception, as most individuals exhibiting signs of lying may experience irregular or erratic breath patterns due to anxiety.