The cart comes way before the horse in the reality series “Married at First Sight.” Based on a hit Danish format, “Married…” features people who agree to participate in an extreme experiment: Each covenants legal marriage with a complete stranger. Specialists — including a spiritualist, a relationship coach and a sociologist — use scientific matchmaking methods to determine each couple, who will not have met or had contact with each other until the wedding day. The series then documents the relationships, including honeymoons and other relatable events of married life. After several weeks, each couple must decide whether to remain together or go their individual ways.