Why might HGN testing provide variable results among different individuals?

HGN testing can yield variable results among different individuals due to individual differences in physical health, which can significantly impact the way a person displays indicators of impairment. Factors such as age, medical conditions, medications, and neurological function can all influence how the eyes move when subjected to the HGN test. For example, someone with a history of brain injuries or certain medical conditions may exhibit nystagmus even without alcohol impairment. Consequently, this variability highlights the importance of considering an individual’s unique physical health profile during assessment, making it clear why option B is the correct choice. The other options do not accurately capture the complex interaction between health and test results, suggesting misunderstood or incorrect premises about universal responses or conditions.