The Problem with Shaping Behavior
Suppose you want your daughter to do her homework. From the behavioristic perspective, you reward her when she does her homework, and/or punish her when she does not, thereby "shaping" the proper behavior – a homework-doing daughter. (I am using "shaping" to describe the overall process of changing behavior to fit some desired goal.)
The dominant theory of most parents seems to be to use rewards and punishments to shape their child's behavior. So children are shaped into sharing, being polite, being responsible, etc.
But then what? Have you accomplished anything? What happens when you are gone?
If you are only concerned with behavior, then you have succeeded – your daughter is doing homework. But parents are concerned with turning their children into responsible adults. Has this been accomplished, if your daughter will stop doing her homework the second you are not there to provide rewards and punishments? No.
Habit
As noted elsewhere, there is the hope that doing his/her homework will prove to be naturally rewarding. This seems unlikely -- if homework was naturally rewarding for your child, you wouldn't need to shape behavior.
There is another hope for continuation of the behavior you have shaped. Lay people call it habit; psychologists call it automatic behavior. If you repeat a behavior over and over, then it becomes a habit and that behavior can occur without thinking (in the same situation). For example, you keep your silverware in a particular drawer, so reaching into that drawer for silverware (when you want silverware) has become a habit. If you move your silverware to a different drawer, you will know in memory that the silverware is moved, but you will find yourself constantly opening the old drawer.
So, if can get your child in the habit of doing homework, the behavior should persist. At least for a while.
However, it is not clear how well rewards and punishments produce habits. I remember when my daughter was about 3 and I had to listen to all the mothers reminding their children to say "thank you." I was leaving a water park, I had some unused tickets, so I gave them to a nearby girl about 11 years old. She was happy to get them. Her mother reminded her to say thank you. I thought, "Does it never stop?"
In any case, habits aren't forever. For example, if you move your silverware drawer, you will sooner or later learn to look in the new place when you want silverware.
The Negative Practice Effect
Okay, suppose you use rewards and/or punishments to get your child to do something you like. Of course, there is some "baseline" of how much your child would do that without your pushing and manipulation. You have "raised behavior above baseline", which is to say, your child is now doing the action more than your child would naturally do it. It could be sharing, homework, practicing the piano, reading, being polite, eating broccoli, whatever.
Unfortunately, you are probably causing your child to dislike the activity. So, if ever remove your rewards and punishments, your child will do it less often (than baseline).
Let me explain. There is a behavioral technique called "negative practice". Suppose there is some behavior that the client is performing but the client does not want to do. This could be smoking, washing his/her hands, some sexual compulsion, or whatever. To use negative practice, you have the client do the action more than the client wants. For example, to quit smoking, Fred Levine started smoking six packs of cigarettes a day instead of his usual three. In behavioral terms, this tends to make the action aversive, which is to say, the client does not want to perform the action. For example, Fred became sick of cigarettes and wanted to quit.
So, you are applying the negative practice technique to your child. For example, by inducing your child to read more than your child likes to, you cause your child to dislike reading.
Negative practice isn't a foolproof technique, and its effect isn't always perfect or permanent. For example, there came a time when Fred wanted a cigarette. But it works reasonably well. The point is, if you are using this technique, you have to expect that the likely effect is to cause your child to dislike the very thing you want your child to do.
There is another way of approaching this issue. It is well-accepted in the behavioral literature that frequency determines how rewarding something is -- if you get a lot of something, then it isn't as rewarding. Suppose there is some food the rat likes, such that the rat will work very hard to get this food. If you give the rat a lot of the food, then the food will not be as rewarding and the rat will not work as hard for the food.
So, if you want your child to, say, enjoy cleaning his/her room, a strategy is to reduce the amount of time your child cleans the room, so that your child is not allowed to clean his/her room as often as he/she likes. Again, if you want your child to dislike cleaning his/her room, you should do something to increase the amount of time your child spends cleaning his/her room.
Extrinsic Rewards Decrease Intrinsic Enjoyment
This is perhaps just another way of approaching the same issue. Deci paid subjects to play with a "Soma Cube". Then the subjects were left alone in the room with the Soma cube and allowed to do whatever they wanted. These subjects played with the Soma Cube
less than subjects who had not been paid to play with the Soma cube.
I think there is more going on than just negative practice. To enjoy a game, you need to become "absorbed" in the game. If you are trying to earn money, your conscious goal is to earn money, so you cannot become absorbed in the game. In fact, you cannot forget your conscious goal, for fear that you will stop playing the game.
So when you play with the Soma cube to earn money, you have a different mind-set then if you are just playing with it for fun. And it is not as good of mind-set, so you are not going to enjoy playing with the Soma cube as much.
I don't think this matters for something like eating brocolli -- a conscious goal to eat it for money probably doesn't interfere with your experience of eating it. So for brocolli, you just get a negative practice effect -- you are forced to eat the brocolli, you don't like the experience, so you dislike brocolli even more.
But this additional effect -- changing the nature of the task to that it is not as enjoyable -- would apply to reading, and it could apply to any complex activity that could be interesting, such as the organizing the clutter in your room.
Do I do this?
Yes. Programs to encourage reading, by rewarding children for reading, are widespread. If my daughters want to participate, they are allowed to. But before letting them, I remind them that reading is supposed to be fun. If they don't want to participate, I sigh with relief.
In seventh grade, students got points for reading books. My daughter is set the record for most points earned. She likes to read.
I never force my children to share. If I insist that one daughter give the other daughter something, I don't call it sharing. When I am embarassed that my child has not said thank you, I might say "I supposed we shouldn't say thank you." But in first grade my student thanked the teacher for awarding her student of the month and the teacher said that was the first time she had ever been thanked for this.