If you tell a child not to do something, chances are he or she will do it. This is a simple rule of parenting that everyone has experienced at some point in their lives. People (especially children and teenagers) are wired in a certain way so that if they are told they cannot do or have something, they react by wanting it more. They then rebel by reasserting their freedom and express anger towards the person restricting their freedom. This is a natural response for a person that is beginning to develop a sense of self and ego, as they feel an instinctive desire to protect their right to free will. This psychological phenomenon is known as reactance.
Although reactance can be very troublesome and annoying to deal with, you can easily turn it around to your advantage if you understand the basic principles behind the effect. Under the assumption that a child will always react to your commands and advice by doing the opposite, we can deduce that if you say the opposite of what you want, they will end up doing what you want. This is reverse psychology. It is a surprisingly effective method of manipulation, especially in those with high reactance (usually children or those who are as immature and stubborn as children).
It has been scientifically proven that reverse psychology is extremely effective in children, as they would rather protect their (perceived) free will than avoiding study or not eating their greens. An example of reverse psychology would be telling a child to stay home when they actually want them to go out and play. However, reverse psychology is not the most ideal way of parenting as it reinforces the idea that it is okay to do the opposite of what you ask, thus undermining your authority.
Reverse psychology works just as well in adults when used right. For example, using a strong imperative tone against a person effectively assaults their ego, which provokes their natural instinct of reactance. If you are not in a position of authority and the person has the option to defy you, it is likely that they will revert to an irrational teenager and do the opposite of what you commanded. However, repetitive use of reverse psychology may lead the person to think that they are being manipulated, causing them to nullify it by reverse reverse psychology. Reverse psychology can be a double-edged sword if this happens, so it is important to know when it is most likely to be effective.
Psychological reactance is more likely to arise if the restricted option appears more attractive and important. The greater the restriction of freedom, the greater the psychological reactance. Also, arbitrary threats produce high reactance as they do not make sense, making people more rebellious. It is important that reverse psychology be used subtly and sparingly on people who are resistant to direct requests. Mastery of the above skills will help you manipulate a person into doing your bidding under the illusion that they are acting on their free will.