Background: It is well-known that Type A behavior pattern is characterized by hard-driving, competitive behavior and time urgency. Also, people with hyperthymic temperament are known to have high energy levels and are full of plans. It is therefore hypothesized that hyperthymic temperament is associated with rapid processing and fast reaction time in making decisions. Methods: Using data from our previous experimental studies(N¼58) examining brightness judgment and brightness preference, reactiontime (RT) was investigated in relation to hyperthymic temperament scores and fMRI signal changes of the left inferior orbito frontal cortex during brightness judgment. Results: RT for brightness judgment was significantly shorter than RT for brightness preference. Significant associations were found between RT for brightness preference and hyperthymic temperament scores, and RT for brightness preference and fMRI signal changes of the left inferior orbito frontal cortex whilst performing brightness preference task. Multiple regression analysis revealed that RT for brightness preference task was significantly and negatively associated with hyperthymic temperament scores, and significantly and positively associated with fMRI signal changes of the left inferior orbito frontal cortex. Limitations: It is uncertain whether the findings of RT (around1s) can be extrapolated to routine life (around24h) and whether RT for brightness preference can be generalized to avariety of daily activities. Conclusions: The present findings suggest that hyperthymic temperament is associated with rapid processing. Further studies are required to overcome the above limitations.