This is from 59 Seconds by Richard Wiseman on discipline:
"If you happen to find yourself in the company of a child who is struggling with such skills, what is the best way of helping them control their impulses and behave themselves? Is it better, for example, to play good cop (?Would you be a little darling and please spend only thirty minutes on the computer??) or to adopt a more threatening approach (?If you don?t get off the computer now, that optical mouse is going right up your USB port?). In the mid-1960s, Jonathan Freedman from Stanford University conducted an experiment on this issue.
His study involved a group of about forty boys, between seven and ten years of age, who were attending one of two
local schools in California. One at a time, the boys were invited into a room and asked to rate the degree to which they liked five toys by assigning each one a number between 0 (?very, very bad toy?) and 100 (?very, very good toy?). Four of the toys were fairly mundane: a cheap plastic submarine, a child?s baseball glove, a toy tractor, and a Dick Tracy toy rifle. In contrast, the fifth toy was far more expensive and exciting. This was a toy among toys, a battery-controlled robot that represented the very height of 1960s technological wonder.
After the boy completed the ratings, the researcher explained that he had an errand to run and so would have to
leave the room for a few minutes. He told the boy that he was free to play with four of the toys but was not to
touch the robot. Half of the boys were clearly told that bad things would happen if they disobeyed the experimenter (?If you play with the robot, I?ll be very angry and will have to do something about it?), while the other half were subjected to a more ?softly, softly? approach (?Do not play with the robot. It is wrong to play with the robot?). The experimenter then left, leaving the boy staring longingly at the robot and its ?come and play with me? flashing eyes. About five minutes later, the experimenter returned, thanked the boy for taking part, and allowed him to leave.
Did the boys succumb to temptation? To find out, the researchers had fitted the robot with a secret device that
measured whether the toy had been turned on. The data revealed that only two of the boys had the self-control to
leave the robot alone. One of the boys came from the group that had been given stern instructions not to play with
the robot, while the other was from the group that had been subjected to the ?softly, softly? approach. When the experimenter was not present to enforce the instruction not to play with the robot, both approaches proved equally
ineffective.
However, Freedman hadn?t expected any real difference in the short term. He was far more interested in differences
that might emerge over a long period of time. About six weeks later, he sent a female experimenter back to the schools, apparently to conduct a different study with the same boys. Each boy was invited into the room and
asked to make a drawing. Exactly the same collection of toys had been placed in the corner of the room, and when
the children had finished their drawings,the experimenter explained that they could now spend a few minutes
playing with any of the toys. This time, none of the toys were designated out of bounds, and so all of them were up for grabs. A big difference emerged between the two groups. Of those in the ?I?ll be really angry and will have to do something about it? group, 77 percent played with the robot, compared to just 33 percent of those in the ?softly, softly? group. Remarkably, just a slight change from the experimenter?s instructions of several weeks earlier had had a significant impact on the boys? subsequent behavior, with the softer wording producing far more
compliance.
Why the big difference? There are several possible explanations. According to some researchers, it has to do
with people?s response to threats. Normally, people need to be threatened only when someone does not want
them to do something that they want to do. And the more they want to do something, the bigger the threat needs
to be to prevent them from doing it. According to this approach, the children who heard the stronger threats would
have unconsciously thought, ?Wow, people only give out big threats like that when I really want to do something that they don?t want me to do, so I must really want to play with the robot.? Using the same logic, a quiet request to the other boys that they not play with the robot resulted in their convincing themselves that they
didn?t really want to play with the toy.
Other researchers argue that the threat instantly elevated the robot to the status of forbidden fruit and elicited
the age-old tendency to want to do something because it is not permitted. Although academic arguments rage about whether this tendency is driven by a sense of curiosity, stubbornness, or rebellion, everyone agrees that the effect is powerful and reliable, and explains why attempts to ban teenage smoking, drinking, and fast driving frequently backfire.
In the secret science of self-discipline, the truth is that some children have an almost innate ability to control their impulses, whereas others find it difficult to resist instant gratification. And to instill self-discipline in those who grab the single marshmallow rather than waiting for two later, it?s clear that the smaller the threat you make, the bigger the impact.
...
Threats work well in the short term but can actually prove counterproductive over longer periods of time. By pointing out all of the terrible things that will happen if your child follows a course of action, you may be making that activity more attractive in their minds. Instead, try the ?softly, softly? approach used in
the toy robot experiment. State that you do not want them to do something and leave it there. If they really do insist on knowing why you are stopping them, try to get them to identify some possible reasons themselves."