A very good article in the New Yorl Times about conditionnal and unconditional parenting, by Alfie Kohn, author of 11 books about human behavior and education, including Unconditional Parenting and Punished by Rewards :
More than 50 years ago, the psychologist Carl Rogers suggested that simply loving our children wasn’t enough. We have to love them unconditionally, he said — for who they are, not for what they do.
[...] this is a tall order, but it becomes even more challenging now that so much of the advice we are given amounts to exactly the opposite. In effect, we’re given tips in conditional parenting, which comes in two flavors: turn up the affection when they’re good, withhold affection when they’re not.
[...] Conditional parenting isn’t limited to old-school authoritarians. Some people who wouldn’t dream of spanking choose instead to discipline their young children by forcibly isolating them, a tactic we prefer to call “time out.” Conversely, “positive reinforcement” teaches children that they are loved, and lovable, only when they do whatever we decide is a “good job.”
[...] studies found that both positive and negative conditional parenting were harmful, but in slightly different ways. The positive kind sometimes succeeded in getting children to work harder on academic tasks, but at the cost of unhealthy feelings of “internal compulsion.” Negative conditional parenting didn’t even work in the short run; it just increased the teenagers’ negative feelings about their parents.
[...] In practice, according to an impressive collection of data by Dr. Edward L. Deci and others, unconditional acceptance by parents as well as teachers should be accompanied by “autonomy support”: explaining reasons for requests, maximizing opportunities for the child to participate in making decisions, being encouraging without manipulating, and actively imagining how things look from the child’s point of view.