We assessed a possible link between the Introversion/Extraversion spectrum and sensori-motor gating and predicted self-reported introverts would have more sensitive sensori-motor gating pathways than extraverts at the individual subject level. 28 subjects self-identified as introverts or extraverts; individuals that self-identified as both introverted and extraverted were classified as ambiverts . Participants\u27orbicularis oculus muscles were electromyographically measured while abrupt auditory stimuli ranging from 50 to 100 decibels were played over headphones. As predicted, introverts exhibited greater electromyographical frequencies and magnitudes of response to stimuli at almost all levels of stimulus intensity. These results indicate introverts tend to be more sensitive, on a physiological level, to incoming stimuli compared to extraverts; this finding counters explanations of introversion as a purely social construct. Interestingly, a further and unpredicted pattern of three distinct groups was also observed. These groups are not organized along the lines of introversion/extraversion and may be linked to the concept of neuroticism
