We pay for most things in money or attention, often exchanging one for the other. But we mistakenly view expenditures of attention as "free"
Influence 101: When you see behavior you want more of, acknowledge it & express appreciation. Needn't be effusive, but be direct & timely.
2/ We'd do well to take the opposite view. Attention is the more precious resource by far. We have a finite amount of it in this lifetime.