What is an observable symptom of someone under the influence of stimulants?

Rapid speech is a well-established observable symptom often associated with stimulant use. Stimulants, such as amphetamines or cocaine, increase nervous system activity, leading to heightened energy levels and increased alertness. This acceleration can manifest in various behaviors, one of which is rapid or pressured speech. Individuals under the influence may feel overly talkative and may struggle to maintain a normal conversational pace, often jumping from topic to topic due to their heightened state.

In contrast, symptoms such as a calm demeanor, reduced heart rate, or excessive sleepiness are inconsistent with the effects of stimulants. These symptoms are more typically linked with depressants or sedatives rather than substances that stimulate the central nervous system. Thus, rapid speech serves as a direct indicator of stimulant influence, making it the correct answer.