The part of the brain most related to reasoning, emotional reactions, and personality is the prefrontal cortex. This area is responsible for higher- level cognitive functions including planning, decision-making, emotion regulation, and personality expression. It works closely with other brain structures such as the amygdala, which handles emotional responses like fear and anger, and the hypothalamus, which manages physiological and hormonal reactions related to emotions. Together, these areas form a network that processes and regulates emotional and cognitive reactions, contributing to a person's personality and reasoning abilities.