Research shows we make up our minds about people through unspoken communication within seven seconds of meeting them. (Para. 1)
Meaning: "Research shows within the first seven seconds when we meet someone, we form our opinion about him or her through nonverbal communication."
make up our minds about people: "form our opinions about people". The phrase "make up one's mind" also means "decide". For example,
I haven't made up my mind where to go yet. 我還沒決定去哪兒。
At the age of 8 she made up her mind to become a doctor. 她8歲時就打定主意要成為一名醫生。