We examined how a friend's presence affects a performer's prefrontal activation in daily-life activities using two wireless portable near-infrared spectroscopy (NIRS) devices. Participants played a driving video game either solely in the single group or with a friend in the paired group. The two groups (single and paired) were subdivided according to their game proficiency (low and high). The NIRS data demonstrated a significant interaction of group by proficiency. Low-proficiency players in the paired group showed lower activation than those in the single group, but high-proficiency players did not. In the paired group, high-proficiency players showed higher activation than low-proficiency players, but not in the single group. These results suggest that NIRS detects social presence effects in everyday situations: decreasing prefrontal activation in low-proficiency performers due to tension reduction and increasing prefrontal activation in high-proficiency performers due to increased arousal.
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