Which of the following is a sign of stress or anxiety during SFST?

Elevated heart rate is a recognized physiological response associated with stress or anxiety. When an individual is feeling anxious or under stress, their body may release adrenaline, which can lead to an increased heart rate. This is a common reaction in situations where people perceive a threat or feel under pressure, such as during a field sobriety test. Recognizing the signs of stress or anxiety is crucial for officers administering the SFST, as these factors can influence a person's performance and behavior.

In contrast, casual conversation and a calm demeanor typically indicate that a person is relaxed and comfortable, which would not be associated with stress or anxiety. Consistent test performance reflects a stable state of mental clarity and control, rather than the fluctuations in performance that can arise from anxiety. Therefore, an elevated heart rate is a clear physiological indicator signaling that the individual may be experiencing stress or anxiety during the testing process.