How can distractions influence the outcome of the HGN test?

Distractions can significantly interfere with a subject's ability to maintain focus during the Horizontal Gaze Nystagmus (HGN) test. When a subject is exposed to distractions, their eye behavior can change, which may lead to misinterpretation of the test results. The HGN test relies on observing the way the eyes move in response to a stimulus, typically a pen or another object held at a specific distance. If the subject is distracted—either by environmental factors or by internal thoughts—this may cause them to exhibit nystagmus (involuntary eye movements) that are not due to impairment from substances but rather due to their lack of focus. Thus, the presence of distractions can compromise the accuracy and reliability of the test outcomes.