Like when you are on the phone or interacting on social network with them, they don't necessarily response to you imediately everytime but they never make the absence too long for you to feel awkward.
And they never send voice-mail to you when they know you're in the middle of some important occasions or when you're on the subway, because they know that it will make it very inconvenient for you and thattext is the more appropriate choice.
And while they're pretty good listeners, they also have their own mature thoughts and would love to share them if they think the it suits the situation.
