Fenna Krienen researched these connections.
- She wanted to know if your brain reacts differently to the four combinations.
- She also wanted to know if you base judgments on people depending if they are similar to you or if they are a close friend or relative.
In her research she found that when people answered questions about their friends or family, whether or not they were similar to them, the medial prefrontal cortex (MPFC) was active. The MPFC is the area of the brain that perceives value and regulates social behavior. When people answered and thought about someone they didn't know, but still had commonalities with, the MPFC was not active.

69. The Brain Responds Uniquely To People You Know Personally