A dual only contributes to the team, and usually and most importantly, doesn't interfere with their partner's thinking processes. Non-interference implies not trying to get into the other person's head or to supplant their ideas. On average, this helps to create a conducive environment and or harmonious team but there certainly isn't melding or merger of minds or souls, or functions. I don't often pair duals for many projects because although they often get along with one another, their skill sets are so different that they don't usually pull on the same oars.

a.k.a. I/O