What physical response is described as goose bumps and is an indicator of hallucinogen use?

The correct choice is piloerection, which refers to the physiological response that results in hair follicles contracting, causing the hair to stand upright and creating the sensation commonly known as goose bumps. This response is a result of the autonomic nervous system reacting to various stimuli, including emotional responses and certain drug use, such as hallucinogens.

In the context of hallucinogen use, piloerection can indicate the drug's effects on the body, as these substances alter sensory perception and emotional states, potentially triggering heightened arousal or altered emotional responses. Understanding this can help individuals recognize specific physiological indicators associated with different substances.