Those twins studies constitutes a low-power measurement of effects of whatever it is that parents in the broad population happen to be doing during the time period of the study. It should not be confused with a measurement of the effects of best practice. Many professional and parent-mediated interventions have been shown to have significant effects in random controlled trials or by other means that are not confounded by genetics. As a broad estimate, any intervention that health insurance will pay is such an evidence-based intervention and there are more outside of that category, the standard for which evidence-based intervention are cover vary from state to state, nation to nation. Some of these have long-term effects.

You write "barring...trauma". Is the definition of "trauma" broad enough to capture all the evidence-based interventions?

This reminds me of my significantly downvoted post about AI needing a caregiver.

I think there is something to be learned from 'training natural intelligences' who also try to break out of the box so to speak. But most people here either don't see the connection or consider it obviously wrong.

Thoughts in relation to AI learning...

Parents tend to be a bit obsessed with setting limits. Setting limits is sometimes necessary, but parents tend rely too much on reacting to limit crossings. If you trained a robot by only reacting to limit crossings then the robot might well spend all it's time bouncing off the limit.

Think of a limit as a border on a region of acceptable behavior. The Kazdin method relies on incrementally (in small behavior shaping steps) drawing the child toward the optimal point in that region of acceptable behavior. If you train a robot this way, then the robot will tend stay sufficiently close to the optimal location, well away from the limits.

You mention inner motivation, competing children, conflict/violent outbreaks. I don't think you yet have a proper analysis of this violent behavior.

Indeed. I do not really know why they escalate when they do. I have the feeling that it results from inner motivation to lead and control by the older against the raising resistence of the younger one the one hand and different (incompatible?) emotion regulation of both - namely the older continuously raises the level while the younger handles it relatively smart and cool until he suddenly has enough. Then boom. Trouble is this is a slow process which can go on for a long time below the radar and sometimes not happen at all, e.g. if they don't touch problematic areas esp. competive ones.

I don't think of competition as bad in and of itself.

Neither do I. But their competition is not a friendly one.

But maybe that is an idea I can follow up on. Not trying to shape cooperation (as they do have a lot of that), but reinforcing positive competition. But probably I have to start with simulation to get that started.

It probably the kids motivating each other's behavior. ... so it can be a bit harder to address.

Exactly.

I think the usual approach is to separate the kids.

I had and have to use it often enough. But separating them doesn't help. Except for the moment. As Kazdin writes: It comes too late. Whatever the cause, both will think they won (or at least didn't lose) and thus got their reward. So any punishment (time out) has no effect.

Why do you say "reinforce separating them"?

The only effect it does have is that they are sparated and I do not want to reinforce separation beteween them. I recognize that they can and do learn a lot from their interaction. I don't want to alienate them of each other. And it shouldn't be necessary. They can play and cooperate for hours - if the agree on a topic. And are in not too bad a mood.

Kindness Chart.

I will try it. I will just have to look out that it doesn't degrade into just another competition and superficial kindness.

You mention inner motivation, competing children, conflict/violent outbreaks. I don't think you yet have a proper analysis of this violent behavior.

I don't think of competition as bad in and of itself. Kids can compete to improve in the direction you want them to improve and you can direct sometimes this process merely by directing your attention toward the preferred behavior.

The violent conflicts are probably not caused by inner motivation. It probably the kids motivating each other's behavior. The problem is that, like inner motivation, it's not your behavior that is reinforcing the conflict, so it can be a bit harder to address. The dynamics might be the Patterson Coercive Cycle, only between two siblings rather than a parent and child:

http://www.pendletonpsych.com/doc/parent-child-coercive-cycle.pdf

I think the usual approach is to separate the kids. Why do you say "reinforce separating them"? You probably are not reinforcing the conflict by separating them. It probably puts conflicts on extinction if you put them both in time out.

Otherwise, you'd have to make sure the aggression does not get it's reward. That is possible but seems hard. Or you could come up with alternative behaviors that had the same function as the aggression, but I don't have any good ideas on how to do that, but you could come up with competitions that are less likely to lead to aggression.

Also, this Kindness Chart, or something like it might help:

http://www.netmums.com/parenting-support/parenting-advice/netmums-parenting-course-about-the-courses/getting-the-best-part-2

Inner motivation is a different issue, I think. Typically you change the behavior to a better one that fulfills the same inner motivation.

One thing you did not discuss is fading. Fade tokens to just use praise and positive attention. Fade constant praise to occasional random praise. Random reinforcement makes a habit more robust and less prone to extinction. (I think of fading as moving toward occasionally reminding the kid that the behavior is evidence of his good character, his virtues, but I a not sure that is explicit in Kazdin's book.)

A central idea is catch them being good and reinforce. Then, after a period of constant reinforcement, fade. If the target behavior does not happen then you can't just catch them doing it. So, use methods to get it started: simulation, prompting, token reward charts. (Also, you might shape if starting with some existing behavior.)

Prompting is a technique to get more compliance to commands. Get close to the kid, speak calmly, touch, don't use a question. Avoid prompting more than a few times (3 or 4) without compliance (nagging). Instead, come up with a different strategy.

The term punishment kind of tricky in this context. Kazdin is a behaviorist writing a parenting book. In behaviorism, the term has a different meaning from it's typical use by parents.

In behaviorism, "positive" means adding something, and "negative" means taking something away. A reinforcement increases a behavior, a punishment decreases a behavior. So in behaviorism efficacy is built into the definition, if it does not decrease behavior then it's not a punishment.

In parenting, punishments are typically used incorrectly, overused, have bad side effects. And, most importantly, it's often not the best alternative because research has found better alternatives. Also, parents are reinforced to punish because they tend to be rewarded with short-term reinforcement, so it can be part of a vicious cycle. What parents consider a punishment might actually be reinforcement, for instance (1) yelling at your kid can make you look like a vanquished foe (2) if the kid can divert the parent into a predictable punishment mode, the parent might not follow through on something that the kid wanted to avoid even more.

If I recall correctly, Kazdin's does not tell parents to never use short-term grounding (or withdrawal of privilege), and that's a negative punishment in behaviorism. He says long-term grounding is no more effective and just causes resentment with no extra benefit.

Isn't punishment negative reward? Shouldn't punishment have the same effect as reward but just the opposite sign?

One hypothesis:

When reward happens, the subject gets curious about exactly what they did to earn the reward; they refine their behavior to more efficiently obtain it (explore → exploit mode). But when punishment happens, the subject gets aversive towards the whole general area around the punishment; they take opportunities to avoid the situation associated with it. If getting in a scuffle at school gets me punished at home, that's a good reason to avoid school or home (or telling parents about school) rather than avoiding scuffles.

In the sufficiently general case, the punished person feels they are being punished for being who they are rather than for any specific action. "I can't be myself around you, because you don't like me." This seems like a chance to lead into some pretty nasty stuff.

One thing I wonder about:

What are good ways to reinforce someone for being honest about making mistakes? If kid comes home from school and has the choice of whether to confess that they got in trouble at school, or lie about it, then punishing them if they confess will deter confession. There's a trope that kids stop telling their parents what happens at school because they take their parents' reactions to be aversive or at least embarrassing. "What'd you do at school, dear?" "Oh, nothing ..."

The way it's phrased, it suggests that "money should be only for food and shelter, really". It may not be what you're trying to express, but I read it as having that kind of subtext. That, I believe, is an untenable position. The fact that musical instruments, which are necessary for meeting certain emotional needs, cost money has nothing at all to do with culture converting anything.

Trying to channel Marcuse from memory, here goes: We have a finite need for money. We need it for is adequate food and shelter. But unsatisfied emotional needs can be effectively unbounded. It's possible for the culture to convert the things that money can buy into something that we seek because of unsatisfied emotional needs. From hence flows the unbounded need for money.

Marcuse would substitute "capitalist" for "culture". But perhaps it's just something about human nature. Perhaps it's the dopamine system in our brains. Not sure why it works this way (assuming it does indeed work this way).