Friendships:

Eric Barker:

"So which costly signals do we want to display (and look for) when it comes to true friends? The experts firmly agree on two, the first one is time. Why is time so powerful? Because it's scarce, and scarce = costly. Want to make someone feel special? Do something for them you simply cannot do for others. If I give you an hour of my time every day, I cannot do that for more than twenty-four people. Cannot. End of discussion."