Edit: relevant quotes from the post:

When trying to maintain order in a class, ignore unruly behavior and praise good behavior (Madsen et al. 1968; McNamara 1987).

To help someone improve at dance or sport, ignore poor performance but reward good performance immediately, for example by shouting "Good!" (Buzas & Allyon 1981) The reason you should ignore poor performance if you say "No, you're doing it wrong!" you are inadvertently punishing the effort. A better response to a mistake would be to reinforce the effort: "Good effort! You're almost there! Try once more."

Reward opinion-expressing to get people to express their opinions more often

Now that we all know this, shouldn't we abolish downvotes? From my personal experience the emotional impact of a downvote is extremely frustrating and not helpful at all. The message I get from a downvote is "You are wrong!" or "What you said doesn't agree with the group consensus so we will punish you for it!". I don't see this as constructive in any sense.